ASTM D445-24

Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)

SIGNIFICANCE AND USE
5.1 Many petroleum products, and some non-petroleum materials, are used as lubricants, and the correct operation of the equipment depends upon the appropriate viscosity of the liquid being used. In addition, the viscosity of many petroleum fuels is important for the estimation of optimum storage, handling, and operational conditions. Thus, the accurate determination of viscosity is essential to many product specifications.
SCOPE
1.1 This test method specifies a procedure for the determination of the kinematic viscosity, ν, of liquid petroleum products, both transparent and opaque, by measuring the time for a volume of liquid to flow under gravity through a calibrated glass capillary viscometer. The dynamic viscosity, η, can be obtained by multiplying the kinematic viscosity, ν, by the density, ρ, of the liquid.  
Note 1: For the measurement of the kinematic viscosity and viscosity of bitumens, see also Test Methods D2170 and D2171.
Note 2: ISO 3104 corresponds to Test Method D445 – 03.  
1.2 The result obtained from this test method is dependent upon the behavior of the sample and is intended for application to liquids for which primarily the shear stress and shear rates are proportional (Newtonian flow behavior). If, however, the viscosity varies significantly with the rate of shear, different results may be obtained from viscometers of different capillary diameters. The procedure and precision values for residual fuel oils, which under some conditions exhibit non-Newtonian behavior, have been included.  
1.3 The range of kinematic viscosities covered by this test method is from 0.2 mm2/s to 300 000 mm2/s (see Table A1.1) at all temperatures (see 6.3 and 6.4). The precision has only been determined for those materials, kinematic viscosity ranges and temperatures as shown in the footnotes to the precision section.  
1.4 The values stated in SI units are to be regarded as standard. The SI unit used in this test method for kinematic viscosity is mm2/s, and the SI unit used in this test method for dynamic viscosity is mPa·s. For user reference, 1 mm2/s = 10-6 m2/s = 1 cSt and 1 mPa·s = 1 cP = 0.001 Pa·s.  
1.5 WARNING—Mercury has been designated by many regulatory agencies as a hazardous substance that can cause serious medical issues. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to materials. Use Caution when handling mercury and mercury-containing products. See the applicable product Safety Data Sheet (SDS) for additional information. The potential exists that selling mercury or mercury-containing products, or both, is prohibited by local or national law. Users must determine legality of sales in their location.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Mar-2024
• ICS: 17.060 - Measurement of volume, mass, density, viscosity
• ICS: 75.080 - Petroleum products in general
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.07 - Flow Properties

Relations

• Replaces: ASTM D445-23 - Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
• Effective Date: 01-Apr-2024
• Referred By: ASTM D7415-22 - Standard Test Method for Condition Monitoring of Sulfate By-Products in In-Service Petroleum and Hydrocarbon Based Lubricants by Trend Analysis Using Fourier Transform Infrared (FT-IR) Spectrometry
• Effective Date: 01-Apr-2024
• Referred By: ASTM D7887-20 - Standard Guide for Selection of Substitute, Non-hazardous, Liquid Filling Substances for Packagings Subjected to the United Nations Performance Tests
• Effective Date: 01-Apr-2024
• Referred By: ASTM D7156-24 - Standard Test Method for Evaluation of Diesel Engine Oils in the T-11 Exhaust Gas Recirculation Diesel Engine
• Effective Date: 01-Apr-2024
• Referred By: ASTM D4054-23 - Standard Practice for Evaluation of New Aviation Turbine Fuels and Fuel Additives
• Effective Date: 01-Apr-2024
• Referred By: ASTM D2501-14(2019) - Standard Test Method for Calculation of Viscosity-Gravity Constant (VGC) of Petroleum Oils
• Effective Date: 01-Apr-2024
• Referred By: ASTM D5372-20 - Standard Guide for Evaluation of Hydrocarbon Heat Transfer Fluids
• Effective Date: 01-Apr-2024
• Referred By: ASTM D2414-23a - Standard Test Method for Carbon Black-Oil Absorption Number (OAN)
• Effective Date: 01-Apr-2024
• Referred By: ASTM D6891-23 - Standard Test Method for Evaluation of Automotive Engine Oils in the Sequence IVA Spark-Ignition Engine
• Effective Date: 01-Apr-2024
• Referred By: ASTM D7414-22 - Standard Test Method for Condition Monitoring of Oxidation in In-Service Petroleum and Hydrocarbon Based Lubricants by Trend Analysis Using Fourier Transform Infrared (FT-IR) Spectrometry
• Effective Date: 01-Apr-2024
• Referred By: ASTM D8324-21 - Standard Guide for Selection of Environmentally Acceptable Lubricants for the U.S. Environmental Protection Agency (EPA) Vessel General Permit
• Effective Date: 01-Apr-2024
• Referred By: ASTM D7973-19 - Standard Guide for Monitoring Failure Mode Progression in Plain Bearings
• Effective Date: 01-Apr-2024
• Referred By: ASTM D2170/D2170M-22 - Standard Test Method for Kinematic Viscosity of Asphalts
• Effective Date: 01-Apr-2024
• Referred By: ASTM D4603-18 - Standard Test Method for Determining Inherent Viscosity of Poly(Ethylene Terephthalate) (PET) by Glass Capillary Viscometer
• Effective Date: 01-Apr-2024
• Referred By: ASTM D4057-22 - Standard Practice for Manual Sampling of Petroleum and Petroleum Products
• Effective Date: 01-Apr-2024

Overview

ASTM D445-24 is an internationally recognized standard from ASTM International, specifying the test method for determination of the kinematic viscosity of transparent and opaque liquids, including petroleum products, by using a calibrated glass capillary viscometer. Additionally, it provides a calculation method for dynamic viscosity by multiplying the measured kinematic viscosity by the liquid density.

The standard is essential in petroleum, lubricant, and fuel industries due to the importance of viscosity in equipment operation, storage, and handling. By ensuring consistent viscosity measurements, ASTM D445 supports product specifications, quality control, and compliance with regulatory demands worldwide.

Key Topics

• Scope: ASTM D445-24 applies to both transparent and opaque liquids, primarily covering Newtonian fluids where shear stress and shear rate are proportional, but also includes some guidance for non-Newtonian fuels under certain conditions.
• Measurement: The method involves timing the flow of a specified volume of liquid through a calibrated glass capillary viscometer under gravity at controlled temperatures.
• Viscosity Ranges: Covers a broad kinematic viscosity range from 0.2 mm²/s to 300,000 mm²/s at any temperature, accommodating a wide variety of petroleum and non-petroleum liquids.
• Temperature Control: Emphasizes precise temperature control and accurate temperature measurement for valid results, with guidelines on appropriate equipment such as liquid-in-glass thermometers and digital contact thermometers.
• Calibration and Standards: Requires the use of calibrated equipment and certified viscosity reference standards traceable to ISO 17025 or equivalent laboratory accreditation.
• Sample Preparation: Details careful cleaning, filtration, and air bubble removal procedures, especially for viscous oils or when testing residual fuel oils and special substances.
• Safety: Warns about hazardous substances (e.g., mercury) and urges users to implement appropriate health, safety, and environmental precautions.

Applications

ASTM D445-24 is widely utilized across industries where liquid viscosity impacts performance or safety. Practical uses include:

• Lubricant Specification: Ensuring motor oils, hydraulic fluids, and gear oils meet the required viscosity grades for optimal engine and machinery performance.
• Fuel Quality Control: Verifying fuel viscosity for proper combustion characteristics, efficient fuel pump operation, and reliable fuel transfer, especially in diesel, jet, and marine fuels.
• Petrochemical Processes: Supporting process control and product consistency in refineries and chemical plants by monitoring and adjusting liquid viscosities.
• Product Development: Facilitating research and development of new lubricants and fuel blends by providing repeatable viscosity data.
• Quality Assurance: Serving as a benchmark for acceptance testing and certificate of analysis for raw materials and finished products.
• Regulatory Compliance: Meeting requirements set by international, national, or industry regulators for petroleum and lubricating oil products.

Related Standards

For a comprehensive viscosity measurement program and global alignment, several related standards are often referenced alongside ASTM D445-24:

• ASTM D2170 / D2171: For measurement of kinematic viscosity and dynamic viscosity of asphalts and bitumens.
• ASTM D446: Specifications and operating instructions for glass capillary kinematic viscometers.
• ISO 3104: International equivalent for determination of kinematic viscosity and calculation of dynamic viscosity in petroleum products.
• ISO 3105: Glass capillary viscometers-specifications and operation.
• ASTM D1193 & ISO 3696: Specifications for reagent and analytical water.
• ASTM D2162: Basic calibration practices for master viscometers and viscosity standard oils.
• ISO 17025: General criteria for competence of testing and calibration laboratories.

By following ASTM D445-24 and these related standards, laboratories and industry professionals can ensure precise, reliable, and globally accepted viscosity measurement results for transparent and opaque liquids. This supports product quality, equipment protection, and regulatory conformance across a range of applications.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D445 − 24
Standard Test Method for
Kinematic Viscosity of Transparent and Opaque Liquids
(and Calculation of Dynamic Viscosity)
This standard is issued under the fixed designation D445; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* serious medical issues. Mercury, or its vapor, has been dem-
onstrated to be hazardous to health and corrosive to materials.
1.1 This test method specifies a procedure for the determi-
Use Caution when handling mercury and mercury-containing
nation of the kinematic viscosity, ν, of liquid petroleum
products. See the applicable product Safety Data Sheet (SDS)
products, both transparent and opaque, by measuring the time
for additional information. The potential exists that selling
for a volume of liquid to flow under gravity through a
mercury or mercury-containing products, or both, is prohibited
calibrated glass capillary viscometer. The dynamic viscosity, η,
by local or national law. Users must determine legality of sales
can be obtained by multiplying the kinematic viscosity, ν, by
in their location.
the density, ρ, of the liquid.
1.6 This standard does not purport to address all of the
NOTE 1—For the measurement of the kinematic viscosity and viscosity
safety concerns, if any, associated with its use. It is the
of bitumens, see also Test Methods D2170 and D2171.
responsibility of the user of this standard to establish appro-
NOTE 2—ISO 3104 corresponds to Test Method D445 – 03.
priate safety, health, and environmental practices and deter-
1.2 The result obtained from this test method is dependent
mine the applicability of regulatory limitations prior to use.
upon the behavior of the sample and is intended for application
1.7 This international standard was developed in accor-
to liquids for which primarily the shear stress and shear rates
dance with internationally recognized principles on standard-
are proportional (Newtonian flow behavior). If, however, the
ization established in the Decision on Principles for the
viscosity varies significantly with the rate of shear, different
Development of International Standards, Guides and Recom-
results may be obtained from viscometers of different capillary
mendations issued by the World Trade Organization Technical
diameters. The procedure and precision values for residual fuel
Barriers to Trade (TBT) Committee.
oils, which under some conditions exhibit non-Newtonian
behavior, have been included.
2. Referenced Documents
1.3 The range of kinematic viscosities covered by this test
2.1 ASTM Standards:
2 2
method is from 0.2 mm /s to 300 000 mm /s (see Table A1.1)
D396 Specification for Fuel Oils
at all temperatures (see 6.3 and 6.4). The precision has only
D446 Specifications and Operating Instructions for Glass
been determined for those materials, kinematic viscosity
Capillary Kinematic Viscometers
ranges and temperatures as shown in the footnotes to the
D1193 Specification for Reagent Water
precision section.
D1217 Test Method for Density and Relative Density (Spe-
1.4 The values stated in SI units are to be regarded as
cific Gravity) of Liquids by Bingham Pycnometer
standard. The SI unit used in this test method for kinematic
D1480 Test Method for Density and Relative Density (Spe-
viscosity is mm /s, and the SI unit used in this test method for
cific Gravity) of Viscous Materials by Bingham Pycnom-
dynamic viscosity is mPa·s. For user reference, 1 mm /s =
eter
-6 2
10 m /s = 1 cSt and 1 mPa·s = 1 cP = 0.001 Pa·s.
D1481 Test Method for Density and Relative Density (Spe-
cific Gravity) of Viscous Materials by Lipkin Bicapillary
1.5 WARNING—Mercury has been designated by many
Pycnometer (Withdrawn 2023)
regulatory agencies as a hazardous substance that can cause
1 2
This test method is under the jurisdiction of Committee D02 on Petroleum For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom- contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
mittee D02.07 on Flow Properties. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved April 1, 2024. Published April 2024. Originally the ASTM website.
approved in 1937. Last previous edition approved in 2023 as D445 – 23. DOI: The last approved version of this historical standard is referenced on
10.1520/D0445-24. www.astm.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D445 − 24
D2162 Practice for Basic Calibration of Master Viscometers NIST GMP 11 Good Measurement Practice for Assignment
and Viscosity Oil Standards and Adjustment of Calibration Intervals for Laboratory
Standards
D2170 Test Method for Kinematic Viscosity of Asphalts
NIST Special Publication 811 Guide for the Use of the
D2171 Test Method for Viscosity of Asphalts by Vacuum
International System of Units (SI)
Capillary Viscometer
NIST Special Publication 1088 Maintenance and Validation
D6071 Test Method for Low Level Sodium in High Purity
of Liquid-in-Glass Thermometers
Water by Graphite Furnace Atomic Absorption Spectros-
copy
3. Terminology
D6074 Guide for Characterizing Hydrocarbon Lubricant
3.1 See also International Vocabulary of Metrology.
Base Oils
D6299 Practice for Applying Statistical Quality Assurance
3.2 Definitions:
and Control Charting Techniques to Evaluate Analytical
3.2.1 digital contact thermometer (DCT), n—an electronic
Measurement System Performance device consisting of a digital display and associated tempera-
D6300 Practice for Determination of Precision and Bias ture sensing probe.
3.2.1.1 Discussion—This device consists of a temperature
Data for Use in Test Methods for Petroleum Products,
Liquid Fuels, and Lubricants sensor connected to a measuring instrument; this instrument
measures the temperature-dependent quantity of the sensor,
D6617 Practice for Laboratory Bias Detection Using Single
computes the temperature from the measured quantity, and
Test Result from Standard Material
provides a digital output. This digital output goes to a digital
D6708 Practice for Statistical Assessment and Improvement
display and/or recording device that may be internal or external
of Expected Agreement Between Two Test Methods that
to the device.
Purport to Measure the Same Property of a Material
3.2.1.2 Discussion—The devices are often referred to as a
D8278 Specification for Digital Contact Thermometers for
“digital thermometers,” however the term includes devices that
Test Methods Measuring Flow Properties of Fuels and
sense temperature by means other than being in physical
Lubricants
contact with the media.
E1 Specification for ASTM Liquid-in-Glass Thermometers
3.2.1.3 Discussion—PET is an acronym for portable elec-
E77 Test Method for Inspection and Verification of Ther-
tronic thermometers, a subset of digital contact thermometers
mometers
(DCT).
E563 Practice for Preparation and Use of an Ice-Point Bath
3.3 Definitions of Terms Specific to This Standard:
as a Reference Temperature
3.3.1 automated viscometer, n—apparatus which, in part or
E1750 Guide for Use of Water Triple Point Cells
in whole, has mechanized one or more of the procedural steps
E2593 Guide for Accuracy Verification of Industrial Plati-
indicated in Section 11 or 12 without changing the principle or
num Resistance Thermometers
technique of the basic manual apparatus. The essential ele-
2.2 ISO Standards:
ments of the apparatus in respect to dimensions, design, and
ISO 3104 Petroleum products—Transparent and opaque
operational characteristics are the same as those of the manual
liquids—Determination of kinematic viscosity and calcu-
method.
lation of dynamic viscosity
3.3.1.1 Discussion—Automated viscometers have the capa-
ISO 3105 Glass capillary kinematic viscometers—
bility to mimic some operation of the test method while
Specification and operating instructions
reducing or removing the need for manual intervention or
ISO 3696 Water for analytical laboratory use—Specification
interpretation. Apparatus which determine kinematic viscosity
and test methods
by physical techniques that are different than those used in this
ISO 5725 Accuracy (trueness and precision) of measurement
test method are not considered to be Automated Viscometers.
methods and results
3.3.2 density, n—the mass per unit volume of a substance at
ISO 9000 Quality management and quality assurance
a given temperature.
standards—Guidelines for selection and use
3.3.3 dynamic viscosity, η, n—the ratio between the applied
ISO 17025 General requirements for the competence of
shear stress and rate of shear of a material.
testing and calibration laboratories
3.3.3.1 Discussion—It is sometimes called the coefficient of
2.3 NIST Standards:
dynamic viscosity or absolute viscosity. Dynamic viscosity is a
NIST Technical Note 1297 Guideline for Evaluating and measure of resistance to flow or deformation which constitutes
Expressing the Uncertainty of NIST Measurement Re- a material’s ability to transfer momentum in response to steady
sults or time-dependent external shear forces. Dynamic viscosity has
http://ts.nist.gov/WeightsAndMeasures/upload/GMP_11_Mar_2003.pdf
4 8
Available from American National Standards Institute (ANSI), 25 W. 43rd St., http://www.nist.gov/pml/pubs/sp811/index.cfm
4th Floor, New York, NY 10036, http://www.ansi.org. http://www.nist.gov/pml/pubs/sp1088/index.cfm
5 10
Available from National Institute of Standards and Technology (NIST), 100 International Vocabulary of Metrology — Basic and General Concepts and
Bureau Dr., Stop 3460, Gaithersburg, MD 20899-3460. Associated Terms (VIM), 3rd ed., 2008, http://www.bipm.org/en/publications/
http://physics.nist.gov/cuu/Uncertainty/bibliography.html guides/vim.html.
D445 − 24
the dimension of mass divided by length and time and its SI 6.1.2 Automated Viscometers—Automated apparatus may
unit is pascal times second (Pa·s). Among the transport be used as long as they mimic the physical conditions,
properties for heat, mass, and momentum transfer, dynamic
operations, or processes of the manual apparatus. Any
viscosity is the momentum conductivity. viscometer, temperature measuring device, temperature
control, temperature-controlled bath, or timing device incorpo-
3.3.4 kinematic viscosity, ν, n—the ratio of the dynamic
rated in the automated apparatus shall conform to the specifi-
viscosity (η) to the density (ρ) of a material at the same
cation for these components as stated in Section 6 of this test
temperature and pressure.
method. Flow times of less than 200 s are permitted, however,
3.3.4.1 Discussion—Kinematic viscosity is the ratio be-
a kinetic energy correction shall be applied in accordance with
tween momentum transport and momentum storage. Such
Section 7 on Kinematic Viscosity Calculation of Specifications
ratios are called diffusivities with dimensions of length squared
D446. The kinetic energy correction shall not exceed 3.0 % of
divided by time and the SI unit is metre squared divided by
the measured viscosity. The automated apparatus shall be
second (m /s). Among the transport properties for heat, mass,
capable of determining kinematic viscosity of a certified
and momentum transfer, kinematic viscosity is the momentum
viscosity reference standard within the limits stated in 9.2.1
diffusivity.
and Section 17. The precision has been determined for auto-
3.3.4.2 Discussion—Formerly, kinematic viscosity was de-
mated viscometers tested on the sample types listed in 17.3.1
fined specifically for viscometers covered by this test method
and is no worse than the manual apparatus (that is, exhibits the
as the resistance to flow under gravity. More generally, it is the
same or less variability).
ratio between momentum transport and momentum storage.
3.3.4.3 Discussion—For gravity-driven flow under a given
NOTE 3—Precision and bias of kinematic viscosity measurements for
hydrostatic head, the pressure head of a liquid is proportional
flow times as low as 10 s have been determined for automated instruments
to its density, ρ, if the density of air is negligible compared to
tested with the sample types listed in 17.3.1.
that of the liquid. For any particular viscometer covered by this
6.2 Viscometer Holders—Use viscometer holders to enable
test method, the time of flow of a fixed volume of liquid is
all viscometers which have the upper meniscus directly above
directly proportional to its kinematic viscosity, ν, where
the lower meniscus to be suspended vertically within 1° in all
ν = η ⁄ρ, and η is the dynamic viscosity.
directions. Those viscometers whose upper meniscus is offset
from directly above the lower meniscus shall be suspended
4. Summary of Test Method
vertically within 0.3° in all directions (see Specifications D446
4.1 The time is measured for a fixed volume of liquid to
and ISO 3105).
flow under gravity through the capillary of a calibrated
6.2.1 Viscometers shall be mounted in the constant tempera-
viscometer under a reproducible driving head and at a closely
ture bath in the same manner as when calibrated and stated on
controlled and known temperature. The kinematic viscosity
the certificate of calibration. See Specifications D446, see
(determined value) is the product of the measured flow time
Operating Instructions in Annexes A1–A3. For those viscom-
and the calibration constant of the viscometer. Two such
eters which have Tube L (see Specifications D446) held
determinations are needed from which to calculate a kinematic
vertical, vertical alignment shall be confirmed by using (1) a
viscosity result that is the average of two acceptable deter-
holder ensured to hold Tube L vertical, or (2) a bubble level
mined values.
mounted on a rod designed to fit into Tube L, or (3) a plumb
line suspended from the center of Tube L, or (4) other internal
5. Significance and Use
means of support provided in the constant temperature bath.
5.1 Many petroleum products, and some non-petroleum
6.3 Temperature-Controlled Bath—Use a transparent liquid
materials, are used as lubricants, and the correct operation of
bath of sufficient depth such, that at no time during the
the equipment depends upon the appropriate viscosity of the
measurement of flow time, any portion of the sample in the
liquid being used. In addition, the viscosity of many petroleum
viscometer is less than 20 mm below the surface of the bath
fuels is important for the estimation of optimum storage,
liquid or less than 20 mm above the bottom of the bath.
handling, and operational conditions. Thus, the accurate deter-
6.3.1 Temperature Control—For each series of flow time
mination of viscosity is essential to many product specifica-
measurements, the temperature control of the bath liquid shall
tions.
be such that within the range from 15 °C to 100 °C, the
temperature of the bath medium does not vary by more than
6. Apparatus
60.02 °C of the selected temperature over the length of the
6.1 Viscometers—Use only calibrated viscometers of the
viscometer, or between the position of each viscometer, or at
glass capillary type, capable of being used to determine
the location of the thermometer. For temperatures outside this
kinematic viscosity within the limits of the precision given in
range, the deviation from the desired temperature must not
the precision section.
exceed 60.05 °C.
6.1.1 Viscometers listed in Table A1.1, whose specifications
6.4 Temperature Measuring Devices:
meet those given in Specifications D446 and in ISO 3105 meet
these requirements. It is not intended to restrict this test method 6.4.1 Liquid-in-glass Thermometers—Use calibrated ther-
mometers noted in Annex A2. Devices with a nominal tem-
to the use of only those viscometers listed in Table A1.1.
Annex A1 gives further guidance. perature range from 0 °C to 100 °C will have an accuracy after
D445 − 24
correction of 60.02 °C or better. When the nominal tempera- accomplished with the use of a water triple point cell, an ice
ture range is outside the 0 °C to 100 °C range, they will have bath, or other suitable constant temperature device which has a
an accuracy after correction of 60.05 °C or better.
known temperature value of suitable precision. See Practice
6.4.1.1 If calibrated liquid-in-glass thermometers are used,
E563 and Guides E1750 and E2593 for more information
the use of two thermometers is recommended. When the
regarding checking calibrations.
temperature range is from 0 °C to 100 °C, the two
6.4.2.2 In the case of constant temperature baths used in
thermometers, with corrections applied, shall agree within
instruments for automatic viscosity determinations, the user is
0.04 °C. When the temperature range is outside 0 °C to 100 °C,
to contact the instrument manufacturer for the correct DCT that
the two thermometers, with corrections applied, shall agree to
has performance equivalence to that described here.
within 0.1 °C.
6.4.3 Outside the range from 0 °C to 100 °C, use either
6.4.2 Digital Contact Thermometer—Use the indicated
calibrated liquid-in-glass thermometers of an accuracy after
DCT for the following nominal temperature ranges:
correction of 60.05 °C or better, or any other thermometric
Nominal Temperature Range Specification D8278 DCT Id
device of equal or better accuracy. When two temperature
–80 °C to 0 °C D02-DCT04
0 °C to 100 °C D02-DCT05
measuring devices are used in the same bath, they shall agree
100 °C to 175 °C D02-DCT06
within 60.1 °C.
6.4.2.1 Verify the calibration at least annually. The probe
6.4.4 Temperature Device Placement:
shall be recalibrated when the check value differs by more than
0.02 °C from the last probe calibration. Verification can be
FIG. 1 Temperature Probe Immersion in Constant Temperature Bath
D445 − 24
6.4.4.1 Liquid-in-glass Thermometer, shall be suspended 7. Reagents and Materials
vertically and positioned so that the top of the liquid column is
7.1 Chromic Acid Cleaning Solution, or a nonchromium-
just below the surface of the bath fluid. See Fig. 1.
containing, strongly oxidizing acid cleaning solution.
6.4.4.2 DCT Probe, shall be immersed by more than its
(Warning—Chromic acid is a health hazard. It is toxic, a
minimum immersion depth in a constant temperature bath so
recognized carcinogen, highly corrosive, and potentially haz-
that the center of the probe’s sensing region is at the same level
ardous in contact with organic materials. If used, wear a full
as the lower half of the working capillary provided the probe’s
face-shield and full-length protective clothing including suit-
minimum immersion depth is met and is no less than indicated
able gloves. Avoid breathing vapor. Dispose of used chromic
on calibration certificate. See Fig. 1. The end of the probe
acid carefully as it remains hazardous. Nonchromium-
sheath shall not extend past the bottom of the viscometer. It is
containing, strongly oxidizing acid cleaning solutions are also
preferable for the center of the sensing element to be located at
highly corrosive and potentially hazardous in contact with
the same level as the lower half of the working capillary as
organic materials, but do not contain chromium which has
long as the minimum immersion requirements are met.
special disposal problems.)
6.4.5 When using liquid-in-glass thermometers, such as
7.2 Sample Solvent, completely miscible with the sample.
those in Table A2.1, use a magnifying device to read the
Filter before use.
thermometer to the nearest ⁄5 division (for example, 0.01 °C or
7.2.1 For most samples, a volatile petroleum spirit or
0.02 °F) to ensure that the required test temperature and
naphtha is suitable. For residual fuels, a prewash with an
temperature control capabilities are met (see 10.1). It is
aromatic solvent such as toluene or xylene may be necessary to
recommended that thermometer readings (and any corrections
remove asphaltenic material.
supplied on the certificates of calibrations for the thermom-
eters) be recorded on a periodic basis to demonstrate compli-
7.3 Drying Solvent, a volatile solvent miscible with the
ance with the test method requirements. This information can
sample solvent (see 7.2) and water (see 7.4). Filter before use.
be quite useful, especially when investigating issues or causes
7.3.1 Acetone is suitable. (Warning—Extremely flam-
relating to testing accuracy and precision.
mable.)
6.5 Timing Device for Manual Viscometers—Use any timing
7.4 Water, deionized or distilled and conforming to Speci-
device, mechanical (spring-wound or motor driven) or digital,
fication D1193 or Grade 3 of ISO 3696. Filter before use.
that is capable of taking readings with a discrimination of 0.1 s
or better and has an accuracy within 60.07 % (see Annex A3)
8. Certified Viscosity Reference Standards
of the reading when tested over the minimum and maximum
8.1 Certified viscosity reference standards shall be certified
intervals of expected flow times.
by a laboratory that has been shown to meet the requirements
6.5.1 Timing devices powered by alternating electric current
of ISO 17025 by independent assessment. Viscosity standards
motors may be used if the current frequency is controlled to an
shall be traceable to master viscometer procedures described in
accuracy of 0.05 % or better. Alternating currents, as provided
Practice D2162.
by some public power systems, are intermittently rather than
8.2 The uncertainty of the certified viscosity reference
continuously controlled. When used to actuate electrical timing
standard shall be stated for each certified value (k = 2, 95 %
devices, such control can cause large errors in kinematic
confidence). See ISO 5725 or NIST 1297.
viscosity flow time measurements.
6.5.2 Timing devices employed in automated viscometers
9. Calibration and Verification
are an integral part of the apparatus and typically are digital
(using a precision crystal oscillator) with discriminations of
9.1 Viscometers—Use only calibrated viscometers,
0.01 s or better. As such, the timing devices are included within
thermometers, and timers as described in Section 6.
the overall system calibration of automated viscometers. Fol-
9.2 Certified Viscosity Reference Standards (Table A1.2)—
low the manufacturer’s instructions for ensuring the automated
These are for use as confirmatory checks on the procedure in
viscometer is properly calibrated using CRM’s such that it is
the laboratory.
capable of determining kinematic viscosity of a certified
9.2.1 If the determined kinematic viscosity does not agree
viscosity reference standard within the limits stated in 9.2.1
within the acceptable tolerance band, as calculated from Annex
and Section 17 (see 6.1.2).
A4, of the certified value, recheck each step in the procedure,
6.6 Ultrasonic Bath, Unheated—(optional), with an operat-
including thermometer and viscometer calibration, to locate the
ing frequency between 25 kHz to 60 kHz and a typical power
source of error. Annex A1 gives details of standards available.
output of ≤100 W, of suitable dimensions to hold container(s)
NOTE 4—In previous issues of Test Method D445, limits of 60.35 % of
placed inside of bath, for use in effectively dissipating and
the certified value have been used. The data to support the limit of
removing air or gas bubbles that can be entrained in viscous
60.35 % cannot be verified. Annex A4 provides instructions on how to
sample types prior to analysis. It is permissible to use ultra-
determine the tolerance band. The tolerance band combines both the
sonic baths with operating frequencies and power outputs
uncertainty of the certified viscosity reference standard as well as the
uncertainty of the laboratory using the certified viscosity reference
outside this range, however it is the responsibility of the
standard.
laboratory to conduct a data comparison study to confirm that
results determined with and without the use of such ultrasonic 9.2.1.1 As an alternative to the calculation in Annex A4, the
baths does not materially impact results. approximate tolerance bands in Table 1 may be used.
D445 − 24
TABLE 1 Approximate Tolerance Bands
open ends of the viscometer is permitted but not mandatory.
These are designed to prevent water condensation. It is
NOTE 1—The tolerance bands were determined using Practice D6617.
A
essential that they do not set up a pressure differential and
The calculation is documented in Research Report RR:D02-1498.
affect the rate of flow. Before the first use of drying tubes, it is
Viscosity of Reference Material,
Tolerance Band
mm /s
recommended that a certified viscosity reference standard is
< 10 ±0.30 %
used to verify the correct use of the viscometer with and
10 to 100 ±0.32 %
without drying tubes in order to ensure that there is no
100 to 1000 ±0.36 %
1000 to 10 000 ±0.42 % restriction in the flow. When the test temperature is below the
10 000 to 100 000 ±0.54 %
dew point, fill the viscometer in the normal manner as required
> 100 000 ±0.73 %
in 11.1. It is recommended to charge the viscometer outside the
A
Supporting data have been filed at ASTM International Headquarters and may be
bath. To ensure that moisture does not condense or freeze on
obtained by requesting Research Report RR:D02-1498.
the walls of the capillary, draw the test portion into the working
capillary and timing bulb, place rubber stoppers into the tubes
to hold the test portion in place, and insert the viscometer into
the bath. After insertion, allow the viscometer to reach bath
9.2.2 The most common sources of error are caused by
temperature, and then remove the stoppers. When performing
particles of dust lodged in the capillary bore and temperature
manual viscosity determinations, do not use those viscometers
measurement errors. It must be appreciated that a correct result
which cannot be removed from the constant temperature bath
obtained on a standard oil does not preclude the possibility of
for charging the sample portion.
a counterbalancing combination of the possible sources of
10.2.3 Viscometers used for silicone fluids, fluorocarbons,
error.
and other liquids which are difficult to remove by the use of a
9.3 The calibration constant, C, is dependent upon the
cleaning agent, shall be reserved for the exclusive use of those
gravitational acceleration at the place of calibration and this
fluids except during their calibration. Subject such viscometers
must, therefore, be supplied by the standardization laboratory
to calibration checks at frequent intervals. The solvent wash-
together with the instrument constant. Where the acceleration
ings from these viscometers shall not be used for the cleaning
of gravity, g, differs by more than 0.1 %, correct the calibration
of other viscometers.
constant as follows:
C 5 g /g × C (1)
~ !
2 2 1 1
11. Procedure for Transparent Liquids
where the subscripts 1 and 2 indicate, respectively, the
11.1 Although not mandatory, for some transparent liquid
standardization laboratory and the testing laboratory.
sample types such as viscous oils that are prone to having
entrained air or gas bubbles present in the sample, the use of an
10. General Procedure for Kinematic Viscosity
ultrasonic bath (see 6.6) without the heater turned on (if so
equipped) has been found effective in homogenizing and
10.1 Adjust and maintain the viscometer bath at the required
dissipating bubbles typically within 5 min prior to taking a test
test temperature within the limits given in 6.3.1, taking account
specimen for analysis, with no material impact on results.
of the conditions given in Annex A2 and of the corrections
Charge the viscometer in the manner dictated by the design of
supplied on the certificates of calibration for the thermometers.
the instrument, this operation being in conformity with that
10.1.1 Thermometers shall be held in an upright position
employed when the instrument was calibrated. If the sample is
under the same conditions of immersion as when calibrated.
thought or known to contain fibers or solid particles, filter
10.1.2 In order to obtain the most reliable temperature
through a 75 μm screen, either prior to or during charging (see
measurement, it is recommended that two thermometers with
Specifications D446).
valid calibration certificates be used (see 6.4).
10.1.3 They should be viewed with a lens assembly giving
NOTE 5—To minimize the potential of particles passing through the
approximately five times magnification and be arranged to
filter from aggregating, it is recommended that the time lapse between
eliminate parallax errors.
filtering and charging be kept to a minimum.
11.1.1 In general, the viscometers used for transparent
10.2 Select a clean, dry, calibrated viscometer having a
range covering the estimated kinematic viscosity (that is, a liquids are of the type listed in Table A1.1; however, for the
manual measurement of kinematic viscosity of jet fuels at
wide capillary for a very viscous liquid and a narrower
capillary for a more fluid liquid). The flow time for manual –20 °C only suspended-level type viscometers as noted in
Table A1.1 shall be used. The suspended level type viscometer
viscometers shall not be less than 200 s or the longer time
noted in Specifications D446. Flow times of less than 200 s are types used for jet fuel do not require a correction to the
calibration constant for the test temperature being used.
permitted for automated viscometers, provided they meet the
requirements of 6.1.2. 11.1.2 With certain products which exhibit gel-like
behavior, exercise care that flow time measurements are made
10.2.1 The specific details of operation vary for the different
types of viscometers listed in Table A1.1. The operating at sufficiently high temperatures for such materials to flow
freely, so that similar kinematic viscosity results are obtained
instructions for the different types of viscometers are given in
Specifications D446. in viscometers of different capillary diameters.
10.2.2 When the test temperature is below the ambient dew 11.1.3 Allow the charged viscometer to remain in the bath
point, the use of loosely-packed drying tubes affixed to the long enough to reach the test temperature. Where one bath is
D445 − 24
used to accommodate several viscometers, never add or 12. Procedure for Residual Fuel Oils and Opaque
withdraw, or clean a viscometer while any other viscometer is Liquids
in use for measuring a flow time.
12.1 For steam-refined cylinder oils and black lubricating
11.1.4 Because this time will vary for different instruments,
oils, proceed to 12.2 ensuring a thoroughly representative
for different temperatures, and for different kinematic
sample is used. The kinematic viscosity of residual fuel oils
viscosities, establish a safe equilibrium time by trial.
and similar waxy products can be affected by the previous
11.1.4.1 Thirty minutes should be sufficient except for the
thermal history and the following procedure described in
highest kinematic viscosities, however a minimum of 30 min is
12.1.1 to 12.1.8 shall be followed to minimize this.
specifically required for manual analysis of jet fuels at −20 °C.
12.1.1 In general, the viscometers used for opaque liquids
11.1.5 Where the design of the viscometer requires it, adjust
are of the reverse-flow type listed in Table A1.1, C.
the volume of the sample to the mark after the sample has
12.1.2 Heat the sample in the original container at a
reached temperature equilibrium.
temperature between 60 °C and 65 °C for 1 h.
11.2 Use suction (if the sample contains no volatile con- 12.1.3 Place the BS/IP/RF U-tube reverse-flow, or Zeitfuchs
stituents) or pressure to adjust the head level of the test sample Cross-arm, or Lantz-Zeitfuchs type reverse-flow viscometer
to a position in the capillary arm of the instrument about 7 mm for the samples to be tested in the viscometer bath(s) at the
above the first timing mark, unless any other value is stated in required test temperature. If the viscometers are to be charged
the operating instructions for the viscometer. With the sample prior to insertion in the viscometer bath, for example, Cannon
flowing freely, measure, in seconds to within 0.1 s, the time Fenske Opaque, see 12.2.1.
required for the meniscus to pass from the first to the second
12.1.4 Upon completion of step 12.1.2, vigorously stir each
timing mark. If this flow time is less than the specified
sample for approximately 20 s with a glass or steel rod of
minimum (see 10.2), select a viscometer with a capillary of
sufficient length to reach the bottom of the container. For
smaller diameter and repeat the operation.
samples of a very waxy nature or oils of high kinematic
11.2.1 Repeat the procedure described in 11.2 to make a viscosity, it may be necessary to increase the heating tempera-
second measurement of flow time. Record both measurements. ture above 65 °C to achieve proper mixing. The sample should
be sufficiently fluid for ease of stirring and shaking.
11.2.2 From the two measurements of flow time, calculate
two determined values of kinematic viscosity. 12.1.5 Remove the stirring rod and inspect for sludge or
wax adhering to the rod. Continue stirring until there is no
11.2.3 If the two determined values of kinematic viscosity
sludge or wax adhering to the rod.
calculated from the flow time measurements agree within the
stated determinability figure (see 17.1.1) for the product, use 12.1.6 Recap the container tightly and shake vigorously for
the average of these determined values to calculate the kine- 1 min to complete the mixing. To protect the integrity of the
matic viscosity result to be reported. Record the result. If not, sample should a repeat analysis be required, pour sufficient
repeat the measurements of flow times (11.2 to 11.2.2) after a sample to fill two flasks and loosely stopper. (Each flask should
hold sufficient sample to fill two viscometers in order to obtain
thorough cleaning and drying of the viscometers and filtering
(where required, see 11.1) of the sample until the calculated two determinations. The second flask is required to carry out a
repeat analysis.) If a repeat analysis is not a consideration the
kinematic viscosity determinations agree with the stated deter-
minability. next steps can be performed using the original container,
loosely capped.
NOTE 6—Poor determinability can be the result of several factors
12.1.7 Heat the first sample flask or sample container
including: air bubbles trapped in the sample within the viscometer, poor
between 100 °C and 105 °C for 30 min.
temperature stability of the constant temperature bath, particulate con-
tamination in the viscometer, or specimen heterogeneity. Additional
12.1.8 Remove the first sample flask or sample container
sample-specific issues may be conformational changes related to time and
from the heat, close tightly, and shake vigorously for 60 s.
thermal history (incomplete reaction of blended chemistries, re-alignment
of polymeric chains, or outgassing of un-reacted components) or the
12.2 Two determinations of the kinematic viscosity of the
sample is a binary mixture of mixed phases (i.e., there may be precipitated
test material are required. For those viscometers that require a
solids such as waxes in the liquid portion of the sample).
complete cleaning after each flow time measurement, two
11.2.4 If the material or temperature, or both, is not listed in
viscometers must be used. These two determinations are used
17.1.1, use 1.5 % as an estimate of the determinability. to calculate one result. Charge two viscometers in the manner
dictated by the design of the instrument. For example, for the
11.2.5 In automated apparatuses, it is permissible to con-
Lantz-Zeitfuchs Cross-arm or the BS/IP/RF U-tube reverse-
tinue running successive determinations after the initial two
flow viscometers for opaque liquids, filter the sample through
determinations up to a maximum of four, without the need to
a 75 μm filter into two viscometers previously placed in the
clean and dry the viscometer tube in between determinations.
bath. For samples subjected to heat treatment, use a preheated
Choose from any two successive determinations (i.e., 1-2, 2-3,
filter to prevent the sample coagulating during the filtration.
3-4) which meet the corresponding determinability precision
statement for the material type being measured. If two succes- 12.2.1 Viscometers which are charged before being inserted
sive determinations that meet the determinability precision into the bath may need to be preheated in an oven prior to
cannot be found for a sample, suspend execution of this test charging the sample. This is to ensure that the sample will not
method for that sample. See Note 6 for further guidance. be cooled below test temperature.
D445 − 24
12.2.2 After 10 min, adjust the volume of the sample (where 13. Cleaning of Viscometer
the design of the viscometer requires) to coincide with the
13.1 Between successive determinations of kinematic
filling marks as in the viscometer specifications (see Specifi-
viscosity, clean the viscometer thoroughly by several rinsings
cations D446).
with the sample solvent, followed by the drying solvent (see
12.2.3 Allow the charged viscometers enough time to reach
7.3). Dry the tube by passing a slow stream of filtered dry air
the test temperature (see 12.2.1). Where one bath is used to
through the viscometer for 2 min or until the last trace of
accommodate several viscometers, never add or withdraw, or
solvent is removed.
clean a viscometer while any other viscometer is in use for
13.2 If periodic verification of the viscometer calibration
measuring flow time.
using certified viscosity reference standards (see 9.2) is outside
12.3 With the sample flowing freely, measure in seconds to
of the acceptable tolerance band, the viscometer may need to
within 0.1 s, the time required for the advancing ring of contact
be cleaned. Clean the viscometer with the cleaning solution
to pass from the first timing mark to the second. Record the
(Warning—see 7.1), for several hours to remove residual
measurement.
traces of organic deposits, rinse thoroughly with water (7.4)
and drying solvent (see 7.3), and dry with filtered dry air or a
12.3.1 In the case of samples requiring heat treatment
described in 12.1 through 12.1.8, complete the measurements vacuum line. Remove any inorganic deposits by hydrochloric
acid treatment before the use of cleaning acid, particularly if
of flow time within 1 h of completing 12.1.8. Record the
measured flow times. the presence of barium salts is suspected. (Warning—It is
essential that alkaline cleaning solutions are not used as
12.4 Calculate kinematic viscosity, ν, in millimetres squared
changes in the viscometer calibration can occur.)
per second, from each measured flow time. Regard these as two
determined values of kinematic viscosity.
14. Calculation
12.4.1 For residual fuel oils, if the two determined values of
14.1 Calculate each of the determined kinematic viscosity
kinematic viscosity agree within the stated determinability
values, ν and ν , from the measured flow times, t and t , and
1 2 1 2
figure (see 17.1.1), use the average of these determined values
the viscometer constant, C, by means of the following equa-
to calculate the kinematic viscosity result to be reported. This
tion:
constitutes one analysis. Record the result. If a second value
ν 5 C·t (2)
(repeat) is required, then repeat the analysis after thorough
1,2 1,2
cleaning and drying of the viscometers starting from sample
where:
preparation steps 12.1.6 using the second flask. If the original
ν = determined kinematic viscosity values for ν and ν ,
1,2 1 2
container has been conditioned using steps 12.1.2 to 12.1.8,
respectively, mm /s,
then this is not suitable for a repeat analysis. If the calculated
2 2
C = calibration constant of the viscometer, mm /s , and
kinematic viscosities do not agree, repeat the measurements of
t = measured flow times for t and t , respectively, s.
1,2 1 2
flow times after thorough cleaning and drying of the viscom-
Calculate the kinematic viscosity result, ν, as an average of
eters and filtering of the sample. If the material or temperature,
ν and ν (see 11.2.3 and 12.4.1).
1 2
or both, is not listed in 17.1.1, for temperatures between 15 °C
and 100 °C use as an estimate of the determinability 1.0 %, and
14.2 Calculate the dynamic viscosity, η, from the calculated
1.5 % for temperatures outside this range; it must be realized kinematic viscosity, ν, and the density, ρ, by means of the
that these materials can be non-Newtonian, and can contain
following equation:
solids which can come out of solution as the flow time is being
η 5 ν × ρ × 10 (3)
measured.
where:
NOTE 7—Poor determinability can be the result of several factors
η = dynamic viscosity, mPa·s,
including: air bubbles trapped in the sample within the viscometer, poor
ρ = density, kg/m , at the same temperature used for the
temperature stability of the constant temperature bath, particulate con-
determination of the kinematic viscosity, and
tamination in the viscometer, or specimen heterogeneity. Additional
sample-specific issues may be conformational changes related to time and ν = kinematic viscosity, mm /s.
thermal history (incomplete reaction of blended chemistries, re-alignment
14.2.1 The density of the sample can be determined at the
of polymeric chains, or outgassing of un-reacted components) or the
test temperature of the kinematic viscosity determination by an
sample is a binary mixture of mixed phases (i.e., there may be precipitated
solids such as waxes in the liquid portion of the sample).
appropriate method such as Test Method D1217, D1480, or
D1481.
12.4.2 In automated apparatuses, it is permissible to con-
tinue running successive determinations after the initial two
15. Expression of Results
determinations up to a maximum of four, without the need to
15.1 Report the test results for the kinematic or dynamic
clean and dry the viscometer tube in between determinations.
viscosity, or both, to four significant figures, together with the
Choose from any two successive determinations (i.e., 1-2, 2-3,
test temperature.
3-4) which meet the corresponding determinability precision
statement for the material type being measured. If two succes-
16. Report
sive determinations that meet the determinability precision
cannot be found for a sample, suspend execution of this test 16.1 Report the following information:
method for that sample. See Note 7 for further guidance. 16.1.1 Type and identification of the product tested,
D445 − 24
16.1.2 Reference to this test method or a corresponding
Gas oils at 40 °C 0.0013 (y+1)
Jet fuels at –20 °C 0.007608
international standard,
Kerosine, diesel fuels, 0.0037 y (0.37 %)
16.1.3 Result of the test (see Section 15),
biodiesel fuels, and biodiesel
fuel blends at 40 °C
16.1.4 Any deviation, by agreement or otherwise, from the
procedure specified, where: y is the average of determined values being com-
pared.
16.1.5 Date of the test, and
17.1.2 The determinability for used (in-service) formulated
16.1.6 Name and address of the test laboratory.
oils has not been determined, however use a limit of 1.0 % (see
12.4.1) for temperatures between 15 °C and 100 °C.
17. Precision and Bias
17.2 Comparison of Results:
17.1 Comparison of Determined Values:
17.2.1 Repeatability (r)—The difference between successive
17.1.1 Determinability (d)—The difference between succes-
results obtained by the same operator in the same laboratory
sive determined values obtained by the same operator in the
with the same apparatus under constant operating conditions on
same laboratory using the same apparatus for a series of
identical test material would, in the long run, in the normal and
operations leading to a single result, would in the long run, in
correct operation of this test method, exceed the values
the normal and correct operation of this test method, ex
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D445 − 23 D445 − 24
Standard Test Method for
Kinematic Viscosity of Transparent and Opaque Liquids
(and Calculation of Dynamic Viscosity)
This standard is issued under the fixed designation D445; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 This test method specifies a procedure for the determination of the kinematic viscosity, ν, of liquid petroleum products, both
transparent and opaque, by measuring the time for a volume of liquid to flow under gravity through a calibrated glass capillary
viscometer. The dynamic viscosity, η, can be obtained by multiplying the kinematic viscosity, ν, by the density, ρ, of the liquid.
NOTE 1—For the measurement of the kinematic viscosity and viscosity of bitumens, see also Test Methods D2170 and D2171.
NOTE 2—ISO 3104 corresponds to Test Method D445 – 03.
1.2 The result obtained from this test method is dependent upon the behavior of the sample and is intended for application to
liquids for which primarily the shear stress and shear rates are proportional (Newtonian flow behavior). If, however, the viscosity
varies significantly with the rate of shear, different results may be obtained from viscometers of different capillary diameters. The
procedure and precision values for residual fuel oils, which under some conditions exhibit non-Newtonian behavior, have been
included.
2 2
1.3 The range of kinematic viscosities covered by this test method is from 0.2 mm /s to 300 000 mm /s (see Table A1.1) at all
temperatures (see 6.3 and 6.4). The precision has only been determined for those materials, kinematic viscosity ranges and
temperatures as shown in the footnotes to the precision section.
1.4 The values stated in SI units are to be regarded as standard. The SI unit used in this test method for kinematic viscosity is
2 2 -6 2
mm /s, and the SI unit used in this test method for dynamic viscosity is mPa·s. For user reference, 1 mm /s = 10 m /s = 1 cSt
and 1 mPa·s = 1 cP = 0.001 Pa·s.
1.5 WARNING—Mercury has been designated by many regulatory agencies as a hazardous substance that can cause serious
medical issues. Mercury, or its vapor, has been demonstrated to be hazardous to health and corrosive to materials. Use Caution
when handling mercury and mercury-containing products. See the applicable product Safety Data Sheet (SDS) for additional
information. The potential exists that selling mercury or mercury-containing products, or both, is prohibited by local or national
law. Users must determine legality of sales in their location.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
This test method is under the jurisdiction of Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee D02.07
on Flow Properties.
Current edition approved Nov. 1, 2023April 1, 2024. Published November 2023April 2024. Originally approved in 1937. Last previous edition approved in 20212023 as
ɛ2
D445 – 21D445 – 23. . DOI: 10.1520/D0445-23.10.1520/D0445-24.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D445 − 24
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D396 Specification for Fuel Oils
D446 Specifications and Operating Instructions for Glass Capillary Kinematic Viscometers
D1193 Specification for Reagent Water
D1217 Test Method for Density and Relative Density (Specific Gravity) of Liquids by Bingham Pycnometer
D1480 Test Method for Density and Relative Density (Specific Gravity) of Viscous Materials by Bingham Pycnometer
D1481 Test Method for Density and Relative Density (Specific Gravity) of Viscous Materials by Lipkin Bicapillary Pycnometer
(Withdrawn 2023)
D2162 Practice for Basic Calibration of Master Viscometers and Viscosity Oil Standards
D2170 Test Method for Kinematic Viscosity of Asphalts
D2171 Test Method for Viscosity of Asphalts by Vacuum Capillary Viscometer
D6071 Test Method for Low Level Sodium in High Purity Water by Graphite Furnace Atomic Absorption Spectroscopy
D6074 Guide for Characterizing Hydrocarbon Lubricant Base Oils
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measure-
ment System Performance
D6300 Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and
Lubricants
D6617 Practice for Laboratory Bias Detection Using Single Test Result from Standard Material
D6708 Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport
to Measure the Same Property of a Material
D8278 Specification for Digital Contact Thermometers for Test Methods Measuring Flow Properties of Fuels and Lubricants
E1 Specification for ASTM Liquid-in-Glass Thermometers
E77 Test Method for Inspection and Verification of Thermometers
E563 Practice for Preparation and Use of an Ice-Point Bath as a Reference Temperature
E1750 Guide for Use of Water Triple Point Cells
E2593 Guide for Accuracy Verification of Industrial Platinum Resistance Thermometers
2.2 ISO Standards:
ISO 3104 Petroleum products—Transparent and opaque liquids—Determination of kinematic viscosity and calculation of
dynamic viscosity
ISO 3105 Glass capillary kinematic viscometers—Specification and operating instructions
ISO 3696 Water for analytical laboratory use—Specification and test methods
ISO 5725 Accuracy (trueness and precision) of measurement methods and results
ISO 9000 Quality management and quality assurance standards—Guidelines for selection and use
ISO 17025 General requirements for the competence of testing and calibration laboratories
2.3 NIST Standards:
NIST Technical Note 1297 Guideline for Evaluating and Expressing the Uncertainty of NIST Measurement Results
NIST GMP 11 Good Measurement Practice for Assignment and Adjustment of Calibration Intervals for Laboratory Standards
NIST Special Publication 811 Guide for the Use of the International System of Units (SI)
NIST Special Publication 1088 Maintenance and Validation of Liquid-in-Glass Thermometers
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
Available from National Institute of Standards and Technology (NIST), 100 Bureau Dr., Stop 3460, Gaithersburg, MD 20899-3460.
http://physics.nist.gov/cuu/Uncertainty/bibliography.html
http://ts.nist.gov/WeightsAndMeasures/upload/GMP_11_Mar_2003.pdf
http://www.nist.gov/pml/pubs/sp811/index.cfm
http://www.nist.gov/pml/pubs/sp1088/index.cfm
D445 − 24
3. Terminology
3.1 See also International Vocabulary of Metrology.
3.2 Definitions:
3.2.1 digital contact thermometer (DCT), n—an electronic device consisting of a digital display and associated temperature
sensing probe.
3.2.1.1 Discussion—
This device consists of a temperature sensor connected to a measuring instrument; this instrument measures the temperature-
dependent quantity of the sensor, computes the temperature from the measured quantity, and provides a digital output. This digital
output goes to a digital display and/or recording device that may be internal or external to the device.
3.2.1.2 Discussion—
The devices are often referred to as a “digital thermometers,” however the term includes devices that sense temperature by means
other than being in physical contact with the media.
3.2.1.3 Discussion—
PET is an acronym for portable electronic thermometers, a subset of digital contact thermometers (DCT).
3.3 Definitions of Terms Specific to This Standard:
3.3.1 automated viscometer, n—apparatus which, in part or in whole, has mechanized one or more of the procedural steps indicated
in Section 11 or 12 without changing the principle or technique of the basic manual apparatus. The essential elements of the
apparatus in respect to dimensions, design, and operational characteristics are the same as those of the manual method.
3.3.1.1 Discussion—
Automated viscometers have the capability to mimic some operation of the test method while reducing or removing the need for
manual intervention or interpretation. Apparatus which determine kinematic viscosity by physical techniques that are different than
those used in this test method are not considered to be Automated Viscometers.
3.3.2 density, n—the mass per unit volume of a substance at a given temperature.
3.3.3 dynamic viscosity, η, n—the ratio between the applied shear stress and rate of shear of a material.
3.3.3.1 Discussion—
It is sometimes called the coefficient of dynamic viscosity or absolute viscosity. Dynamic viscosity is a measure of resistance to
flow or deformation which constitutes a material’s ability to transfer momentum in response to steady or time-dependent external
shear forces. Dynamic viscosity has the dimension of mass divided by length and time and its SI unit is pascal times second (Pa·s).
Among the transport properties for heat, mass, and momentum transfer, dynamic viscosity is the momentum conductivity.
3.3.4 kinematic viscosity, ν, n—the ratio of the dynamic viscosity (η) to the density (ρ) of a material at the same temperature and
pressure.
3.3.4.1 Discussion—
Kinematic viscosity is the ratio between momentum transport and momentum storage. Such ratios are called diffusivities with
dimensions of length squared divided by time and the SI unit is metre squared divided by second (m /s). Among the transport
properties for heat, mass, and momentum transfer, kinematic viscosity is the momentum diffusivity.
3.3.4.2 Discussion—
Formerly, kinematic viscosity was defined specifically for viscometers covered by this test method as the resistance to flow under
gravity. More generally, it is the ratio between momentum transport and momentum storage.
3.3.4.3 Discussion—
For gravity-driven flow under a given hydrostatic head, the pressure head of a liquid is proportional to its density, ρ, if the density
of air is negligible compared to that of the liquid. For any particular viscometer covered by this test method, the time of flow of
a fixed volume of liquid is directly proportional to its kinematic viscosity, ν, where ν = η ⁄ρ, and η is the dynamic viscosity.
4. Summary of Test Method
4.1 The time is measured for a fixed volume of liquid to flow under gravity through the capillary of a calibrated viscometer under
a reproducible driving head and at a closely controlled and known temperature. The kinematic viscosity (determined value) is the
International Vocabulary of Metrology — Basic and General Concepts and Associated Terms (VIM), 3rd ed., 2008, http://www.bipm.org/en/publications/guides/
vim.html.
D445 − 24
product of the measured flow time and the calibration constant of the viscometer. Two such determinations are needed from which
to calculate a kinematic viscosity result that is the average of two acceptable determined values.
5. Significance and Use
5.1 Many petroleum products, and some non-petroleum materials, are used as lubricants, and the correct operation of the
equipment depends upon the appropriate viscosity of the liquid being used. In addition, the viscosity of many petroleum fuels is
important for the estimation of optimum storage, handling, and operational conditions. Thus, the accurate determination of
viscosity is essential to many product specifications.
6. Apparatus
6.1 Viscometers—Use only calibrated viscometers of the glass capillary type, capable of being used to determine kinematic
viscosity within the limits of the precision given in the precision section.
6.1.1 Viscometers listed in Table A1.1, whose specifications meet those given in Specifications D446 and in ISO 3105 meet these
requirements. It is not intended to restrict this test method to the use of only those viscometers listed in Table A1.1. Annex A1 gives
further guidance.
6.1.2 Automated Viscometers—Automated apparatus may be used as long as they mimic the physical conditions, operations, or
processes of the manual apparatus. Any viscometer, temperature measuring device, temperature control, temperature-controlled
bath, or timing device incorporated in the automated apparatus shall conform to the specification for these components as stated
in Section 6 of this test method. Flow times of less than 200 s are permitted, however, a kinetic energy correction shall be applied
in accordance with Section 7 on Kinematic Viscosity Calculation of Specifications D446. The kinetic energy correction shall not
exceed 3.0 % of the measured viscosity. The automated apparatus shall be capable of determining kinematic viscosity of a certified
viscosity reference standard within the limits stated in 9.2.1 and Section 17. The precision has been determined for automated
viscometers tested on the sample types listed in 17.3.1 and is no worse than the manual apparatus (that is, exhibits the same or
less variability).
NOTE 3—Precision and bias of kinematic viscosity measurements for flow times as low as 10 s have been determined for automated instruments tested
with the sample types listed in 17.3.1.
6.2 Viscometer Holders—Use viscometer holders to enable all viscometers which have the upper meniscus directly above the
lower meniscus to be suspended vertically within 1° in all directions. Those viscometers whose upper meniscus is offset from
directly above the lower meniscus shall be suspended vertically within 0.3° in all directions (see Specifications D446 and ISO
3105).
6.2.1 Viscometers shall be mounted in the constant temperature bath in the same manner as when calibrated and stated on the
certificate of calibration. See Specifications D446, see Operating Instructions in Annexes A1–A3. For those viscometers which
have Tube L (see Specifications D446) held vertical, vertical alignment shall be confirmed by using (1) a holder ensured to hold
Tube L vertical, or (2) a bubble level mounted on a rod designed to fit into Tube L, or (3) a plumb line suspended from the center
of Tube L, or (4) other internal means of support provided in the constant temperature bath.
6.3 Temperature-Controlled Bath—Use a transparent liquid bath of sufficient depth such, that at no time during the measurement
of flow time, any portion of the sample in the viscometer is less than 20 mm below the surface of the bath liquid or less than 20
mm above the bottom of the bath.
6.3.1 Temperature Control—For each series of flow time measurements, the temperature control of the bath liquid shall be such
that within the range from 15 °C to 100 °C, the temperature of the bath medium does not vary by more than 60.02 °C of the
selected temperature over the length of the viscometer, or between the position of each viscometer, or at the location of the
thermometer. For temperatures outside this range, the deviation from the desired temperature must not exceed 60.05 °C.
6.4 Temperature Measuring Devices:
6.4.1 Liquid-in-glass Thermometers—Use calibrated thermometers noted in Annex A2. Devices with a nominal temperature range
from 0 °C to 100 °C will have an accuracy after correction of 60.02 °C or better. When the nominal temperature range is outside
the 0 °C to 100 °C range, they will have an accuracy after correction of 60.05 °C or better.
D445 − 24
6.4.1.1 If calibrated liquid-in-glass thermometers are used, the use of two thermometers is recommended. When the temperature
range is from 0 °C to 100 °C, the two thermometers, with corrections applied, shall agree within 0.04 °C. When the temperature
range is outside 0 °C to 100 °C, the two thermometers, with corrections applied, shall agree to within 0.1 °C.
6.4.2 Digital Contact Thermometer—Use the indicated DCT for the following nominal temperature ranges:
Nominal Temperature Range Specification D8278 DCT Id
–80 °C to 0 °C D02-DCT04
0 °C to 100 °C D02-DCT05
100 °C to 175 °C D02-DCT06
6.4.2.1 Verify the calibration at least annually. The probe shall be recalibrated when the check value differs by more than 0.02 °C
from the last probe calibration. Verification can be accomplished with the use of a water triple point cell, an ice bath, or other
suitable constant temperature device which has a known temperature value of suitable precision. See Practice E563 and Guides
E1750 and E2593 for more information regarding checking calibrations.
6.4.2.2 In the case of constant temperature baths used in instruments for automatic viscosity determinations, the user is to contact
the instrument manufacturer for the correct DCT that has performance equivalence to that described here.
6.4.3 Outside the range from 0 °C to 100 °C, use either calibrated liquid-in-glass thermometers of an accuracy after correction of
60.05 °C or better, or any other thermometric device of equal or better accuracy. When two temperature measuring devices are
used in the same bath, they shall agree within 60.1 °C.
6.4.4 Temperature Device Placement:
6.4.4.1 Liquid-in-glass Thermometer, shall be suspended vertically and positioned so that the top of the liquid column is just below
the surface of the bath fluid. See Fig. 1.
6.4.4.2 DCT Probe, shall be immersed by more than its minimum immersion depth in a constant temperature bath so that the
center of the probe’s sensing region is at the same level as the lower half of the working capillary provided the probe’s minimum
immersion depth is met and is no less than indicated on calibration certificate. See Fig. 1. The end of the probe sheath shall not
extend past the bottom of the viscometer. It is preferable for the center of the sensing element to be located at the same level as
the lower half of the working capillary as long as the minimum immersion requirements are met.
6.4.5 When using liquid-in-glass thermometers, such as those in Table A2.1, use a magnifying device to read the thermometer to
the nearest ⁄5 division (for example, 0.01 °C or 0.02 °F) to ensure that the required test temperature and temperature control
capabilities are met (see 10.1). It is recommended that thermometer readings (and any corrections supplied on the certificates of
calibrations for the thermometers) be recorded on a periodic basis to demonstrate compliance with the test method requirements.
This information can be quite useful, especially when investigating issues or causes relating to testing accuracy and precision.
6.5 Timing Device for Manual Viscometers—Use any timing device, mechanical (spring-wound or motor driven) or digital, that
is capable of taking readings with a discrimination of 0.1 s or better and has an accuracy within 60.07 % (see Annex A3) of the
reading when tested over the minimum and maximum intervals of expected flow times.
6.5.1 Timing devices powered by alternating electric current motors may be used if the current frequency is controlled to an
accuracy of 0.05 % or better. Alternating currents, as provided by some public power systems, are intermittently rather than
continuously controlled. When used to actuate electrical timing devices, such control can cause large errors in kinematic viscosity
flow time measurements.
6.5.2 Timing devices employed in automated viscometers are an integral part of the apparatus and typically are digital (using a
precision crystal oscillator) with discriminations of 0.01 s or better. As such, the timing devices are included within the overall
system calibration of automated viscometers. Follow the manufacturer’s instructions for ensuring the automated viscometer is
properly calibrated using CRM’s such that it is capable of determining kinematic viscosity of a certified viscosity reference
standard within the limits stated in 9.2.1 and Section 17 (see 6.1.2).
6.6 Ultrasonic Bath, Unheated—(optional), with an operating frequency between 25 kHz to 60 kHz and a typical power output
D445 − 24
FIG. 1 Temperature Probe Immersion in Constant Temperature Bath
of ≤100 W, of suitable dimensions to hold container(s) placed inside of bath, for use in effectively dissipating and removing air
or gas bubbles that can be entrained in viscous sample types prior to analysis. It is permissible to use ultrasonic baths with operating
frequencies and power outputs outside this range, however it is the responsibility of the laboratory to conduct a data comparison
study to confirm that results determined with and without the use of such ultrasonic baths does not materially impact results.
7. Reagents and Materials
7.1 Chromic Acid Cleaning Solution, or a nonchromium-containing, strongly oxidizing acid cleaning solution. (Warning—
Chromic acid is a health hazard. It is toxic, a recognized carcinogen, highly corrosive, and potentially hazardous in contact with
organic materials. If used, wear a full face-shield and full-length protective clothing including suitable gloves. Avoid breathing
vapor. Dispose of used chromic acid carefully as it remains hazardous. Nonchromium-containing, strongly oxidizing acid cleaning
solutions are also highly corrosive and potentially hazardous in contact with organic materials, but do not contain chromium which
has special disposal problems.)
7.2 Sample Solvent, completely miscible with the sample. Filter before use.
7.2.1 For most samples, a volatile petroleum spirit or naphtha is suitable. For residual fuels, a prewash with an aromatic solvent
such as toluene or xylene may be necessary to remove asphaltenic material.
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7.3 Drying Solvent, a volatile solvent miscible with the sample solvent (see 7.2) and water (see 7.4). Filter before use.
7.3.1 Acetone is suitable. (Warning—Extremely flammable.)
7.4 Water, deionized or distilled and conforming to Specification D1193 or Grade 3 of ISO 3696. Filter before use.
8. Certified Viscosity Reference Standards
8.1 Certified viscosity reference standards shall be certified by a laboratory that has been shown to meet the requirements of ISO
17025 by independent assessment. Viscosity standards shall be traceable to master viscometer procedures described in Practice
D2162.
8.2 The uncertainty of the certified viscosity reference standard shall be stated for each certified value (k = 2, 95 % confidence).
See ISO 5725 or NIST 1297.
9. Calibration and Verification
9.1 Viscometers—Use only calibrated viscometers, thermometers, and timers as described in Section 6.
9.2 Certified Viscosity Reference Standards (Table A1.2)—These are for use as confirmatory checks on the procedure in the
laboratory.
9.2.1 If the determined kinematic viscosity does not agree within the acceptable tolerance band, as calculated from Annex A4, of
the certified value, recheck each step in the procedure, including thermometer and viscometer calibration, to locate the source of
error. Annex A1 gives details of standards available.
NOTE 4—In previous issues of Test Method D445, limits of 60.35 % of the certified value have been used. The data to support the limit of 60.35 % cannot
be verified. Annex A4 provides instructions on how to determine the tolerance band. The tolerance band combines both the uncertainty of the certified
viscosity reference standard as well as the uncertainty of the laboratory using the certified viscosity reference standard.
9.2.1.1 As an alternative to the calculation in Annex A4, the approximate tolerance bands in Table 1 may be used.
9.2.2 The most common sources of error are caused by particles of dust lodged in the capillary bore and temperature measurement
errors. It must be appreciated that a correct result obtained on a standard oil does not preclude the possibility of a counterbalancing
combination of the possible sources of error.
9.3 The calibration constant, C, is dependent upon the gravitational acceleration at the place of calibration and this must, therefore,
be supplied by the standardization laboratory together with the instrument constant. Where the acceleration of gravity, g, differs
by more than 0.1 %, correct the calibration constant as follows:
C 5 ~g /g !×C (1)
2 2 1 1
where the subscripts 1 and 2 indicate, respectively, the standardization laboratory and the testing laboratory.
TABLE 1 Approximate Tolerance Bands
NOTE 1—The tolerance bands were determined using Practice D6617.
A
The calculation is documented in Research Report RR:D02-1498.
Viscosity of Reference Material,
Tolerance Band
mm /s
< 10 ±0.30 %
10 to 100 ±0.32 %
100 to 1000 ±0.36 %
1000 to 10 000 ±0.42 %
10 000 to 100 000 ±0.54 %
> 100 000 ±0.73 %
A
Supporting data have been filed at ASTM International Headquarters and may be
obtained by requesting Research Report RR:D02-1498.
D445 − 24
10. General Procedure for Kinematic Viscosity
10.1 Adjust and maintain the viscometer bath at the required test temperature within the limits given in 6.3.1, taking account of
the conditions given in Annex A2 and of the corrections supplied on the certificates of calibration for the thermometers.
10.1.1 Thermometers shall be held in an upright position under the same conditions of immersion as when calibrated.
10.1.2 In order to obtain the most reliable temperature measurement, it is recommended that two thermometers with valid
calibration certificates be used (see 6.4).
10.1.3 They should be viewed with a lens assembly giving approximately five times magnification and be arranged to eliminate
parallax errors.
10.2 Select a clean, dry, calibrated viscometer having a range covering the estimated kinematic viscosity (that is, a wide capillary
for a very viscous liquid and a narrower capillary for a more fluid liquid). The flow time for manual viscometers shall not be less
than 200 s or the longer time noted in Specifications D446. Flow times of less than 200 s are permitted for automated viscometers,
provided they meet the requirements of 6.1.2.
10.2.1 The specific details of operation vary for the different types of viscometers listed in Table A1.1. The operating instructions
for the different types of viscometers are given in Specifications D446.
10.2.2 When the test temperature is below the ambient dew point, the use of loosely-packed drying tubes affixed to the open ends
of the viscometer is permitted but not mandatory. These are designed to prevent water condensation. It is essential that they do
not set up a pressure differential and affect the rate of flow. Before the first use of drying tubes, it is recommended that a certified
viscosity reference standard is used to verify the correct use of the viscometer with and without drying tubes in order to ensure
that there is no restriction in the flow. When the test temperature is below the dew point, fill the viscometer in the normal manner
as required in 11.1. It is recommended to charge the viscometer outside the bath. To ensure that moisture does not condense or
freeze on the walls of the capillary, draw the test portion into the working capillary and timing bulb, place rubber stoppers into
the tubes to hold the test portion in place, and insert the viscometer into the bath. After insertion, allow the viscometer to reach
bath temperature, and then remove the stoppers. When performing manual viscosity determinations, do not use those viscometers
which cannot be removed from the constant temperature bath for charging the sample portion.
10.2.3 Viscometers used for silicone fluids, fluorocarbons, and other liquids which are difficult to remove by the use of a cleaning
agent, shall be reserved for the exclusive use of those fluids except during their calibration. Subject such viscometers to calibration
checks at frequent intervals. The solvent washings from these viscometers shall not be used for the cleaning of other viscometers.
11. Procedure for Transparent Liquids
11.1 Although not mandatory, for some transparent liquid sample types such as viscous oils that are prone to having entrained air
or gas bubbles present in the sample, the use of an ultrasonic bath (see 6.6) without the heater turned on (if so equipped) has been
found effective in homogenizing and dissipating bubbles typically within 5 min prior to taking a test specimen for analysis, with
no material impact on results. Charge the viscometer in the manner dictated by the design of the instrument, this operation being
in conformity with that employed when the instrument was calibrated. If the sample is thought or known to contain fibers or solid
particles, filter through a 75 μm screen, either prior to or during charging (see Specifications D446).
NOTE 5—To minimize the potential of particles passing through the filter from aggregating, it is recommended that the time lapse between filtering and
charging be kept to a minimum.
11.1.1 In general, the viscometers used for transparent liquids are of the type listed in Table A1.1; however, for the manual
measurement of kinematic viscosity of jet fuels at –20 °C only suspended-level type viscometers as noted in Table A1.1 shall be
used. The suspended level type viscometer types used for jet fuel do not require a correction to the calibration constant for the test
temperature being used.
11.1.2 With certain products which exhibit gel-like behavior, exercise care that flow time measurements are made at sufficiently
high temperatures for such materials to flow freely, so that similar kinematic viscosity results are obtained in viscometers of
different capillary diameters.
D445 − 24
11.1.3 Allow the charged viscometer to remain in the bath long enough to reach the test temperature. Where one bath is used to
accommodate several viscometers, never add or withdraw, or clean a viscometer while any other viscometer is in use for measuring
a flow time.
11.1.4 Because this time will vary for different instruments, for different temperatures, and for different kinematic viscosities,
establish a safe equilibrium time by trial.
11.1.4.1 Thirty minutes should be sufficient except for the highest kinematic viscosities, however a minimum of 30 min is
specifically required for manual analysis of jet fuels at −20 °C.
11.1.5 Where the design of the viscometer requires it, adjust the volume of the sample to the mark after the sample has reached
temperature equilibrium.
11.2 Use suction (if the sample contains no volatile constituents) or pressure to adjust the head level of the test sample to a position
in the capillary arm of the instrument about 7 mm above the first timing mark, unless any other value is stated in the operating
instructions for the viscometer. With the sample flowing freely, measure, in seconds to within 0.1 s, the time required for the
meniscus to pass from the first to the second timing mark. If this flow time is less than the specified minimum (see 10.2), select
a viscometer with a capillary of smaller diameter and repeat the operation.
11.2.1 Repeat the procedure described in 11.2 to make a second measurement of flow time. Record both measurements.
11.2.2 From the two measurements of flow time, calculate two determined values of kinematic viscosity.
11.2.3 If the two determined values of kinematic viscosity calculated from the flow time measurements agree within the stated
determinability figure (see 17.1.1) for the product, use the average of these determined values to calculate the kinematic viscosity
result to be reported. Record the result. If not, repeat the measurements of flow times (11.2 to 11.2.2) after a thorough cleaning
and drying of the viscometers and filtering (where required, see 11.1) of the sample until the calculated kinematic viscosity
determinations agree with the stated determinability.
NOTE 6—Poor determinability can be the result of several factors including: air bubbles trapped in the sample within the viscometer, poor temperature
stability of the constant temperature bath, particulate contamination in the viscometer, or specimen heterogeneity. Additional sample-specific issues may
be conformational changes related to time and thermal history (incomplete reaction of blended chemistries, re-alignment of polymeric chains, or
outgassing of un-reacted components) or the sample is a binary mixture of mixed phases (i.e., there may be precipitated solids such as waxes in the liquid
portion of the sample).
11.2.4 If the material or temperature, or both, is not listed in 17.1.1, use 1.5 % as an estimate of the determinability.
11.2.5 In automated apparatuses, it is permissible to continue running successive determinations after the initial two
determinations up to a maximum of four, without the need to clean and dry the viscometer tube in between determinations. Choose
from any two successive determinations (i.e., 1-2, 2-3, 3-4) which meet the corresponding determinability precision statement for
the material type being measured. If two successive determinations that meet the determinability precision cannot be found for a
sample, suspend execution of this test method for that sample. See Note 6 for further guidance.
12. Procedure for Residual Fuel Oils and Opaque Liquids
12.1 For steam-refined cylinder oils and black lubricating oils, proceed to 12.2 ensuring a thoroughly representative sample is
used. The kinematic viscosity of residual fuel oils and similar waxy products can be affected by the previous thermal history and
the following procedure described in 12.1.1 to 12.1.8 shall be followed to minimize this.
12.1.1 In general, the viscometers used for opaque liquids are of the reverse-flow type listed in Table A1.1, C.
12.1.2 Heat the sample in the original container at a temperature between 60 °C and 65 °C for 1 h.
12.1.3 Place the BS/IP/RF U-tube reverse-flow, or Zeitfuchs Cross-arm, or Lantz-Zeitfuchs type reverse-flow viscometer for the
samples to be tested in the viscometer bath(s) at the required test temperature. If the viscometers are to be charged prior to insertion
in the viscometer bath, for example, Cannon Fenske Opaque, see 12.2.1.
D445 − 24
12.1.4 Upon completion of step 12.1.2, vigorously stir each sample for approximately 20 s with a glass or steel rod of sufficient
length to reach the bottom of the container. For samples of a very waxy nature or oils of high kinematic viscosity, it may be
necessary to increase the heating temperature above 65 °C to achieve proper mixing. The sample should be sufficiently fluid for
ease of stirring and shaking.
12.1.5 Remove the stirring rod and inspect for sludge or wax adhering to the rod. Continue stirring until there is no sludge or wax
adhering to the rod.
12.1.6 Recap the container tightly and shake vigorously for 1 min to complete the mixing. To protect the integrity of the sample
should a repeat analysis be required, pour sufficient sample to fill two flasks and loosely stopper. (Each flask should hold sufficient
sample to fill two viscometers in order to obtain two determinations. The second flask is required to carry out a repeat analysis.)
If a repeat analysis is not a consideration the next steps can be performed using the original container, loosely capped.
12.1.7 Heat the first sample flask or sample container between 100 °C and 105 °C for 30 min.
12.1.8 Remove the first sample flask or sample container from the heat, close tightly, and shake vigorously for 60 s.
12.2 Two determinations of the kinematic viscosity of the test material are required. For those viscometers that require a complete
cleaning after each flow time measurement, two viscometers must be used. These two determinations are used to calculate one
result. Charge two viscometers in the manner dictated by the design of the instrument. For example, for the Lantz-Zeitfuchs
Cross-arm or the BS/IP/RF U-tube reverse-flow viscometers for opaque liquids, filter the sample through a 75 μm filter into two
viscometers previously placed in the bath. For samples subjected to heat treatment, use a preheated filter to prevent the sample
coagulating during the filtration.
12.2.1 Viscometers which are charged before being inserted into the bath may need to be preheated in an oven prior to charging
the sample. This is to ensure that the sample will not be cooled below test temperature.
12.2.2 After 10 min, adjust the volume of the sample (where the design of the viscometer requires) to coincide with the filling
marks as in the viscometer specifications (see Specifications D446).
12.2.3 Allow the charged viscometers enough time to reach the test temperature (see 12.2.1). Where one bath is used to
accommodate several viscometers, never add or withdraw, or clean a viscometer while any other viscometer is in use for measuring
flow time.
12.3 With the sample flowing freely, measure in seconds to within 0.1 s, the time required for the advancing ring of contact to
pass from the first timing mark to the second. Record the measurement.
12.3.1 In the case of samples requiring heat treatment described in 12.1 through 12.1.8, complete the measurements of flow time
within 1 h of completing 12.1.8. Record the measured flow times.
12.4 Calculate kinematic viscosity, ν, in millimetres squared per second, from each measured flow time. Regard these as two
determined values of kinematic viscosity.
12.4.1 For residual fuel oils, if the two determined values of kinematic viscosity agree within the stated determinability figure (see
17.1.1), use the average of these determined values to calculate the kinematic viscosity result to be reported. This constitutes one
analysis. Record the result. If a second value (repeat) is required, then repeat the analysis after thorough cleaning and drying of
the viscometers starting from sample preparation steps 12.1.6 using the second flask. If the original container has been conditioned
using steps 12.1.2 to 12.1.8, then this is not suitable for a repeat analysis. If the calculated kinematic viscosities do not agree, repeat
the measurements of flow times after thorough cleaning and drying of the viscometers and filtering of the sample. If the material
or temperature, or both, is not listed in 17.1.1, for temperatures between 15 °C and 100 °C use as an estimate of the determinability
1.0 %, and 1.5 % for temperatures outside this range; it must be realized that these materials can be non-Newtonian, and can
contain solids which can come out of solution as the flow time is being measured.
NOTE 7—Poor determinability can be the result of several factors including: air bubbles trapped in the sample within the viscometer, poor temperature
stability of the constant temperature bath, particulate contamination in the viscometer, or specimen heterogeneity. Additional sample-specific issues may
be conformational changes related to time and thermal history (incomplete reaction of blended chemistries, re-alignment of polymeric chains, or
D445 − 24
outgassing of un-reacted components) or the sample is a binary mixture of mixed phases (i.e., there may be precipitated solids such as waxes in the liquid
portion of the sample).
12.4.2 In automated apparatuses, it is permissible to continue running successive determinations after the initial two
determinations up to a maximum of four, without the need to clean and dry the viscometer tube in between determinations. Choose
from any two successive determinations (i.e., 1-2, 2-3, 3-4) which meet the corresponding determinability precision statement for
the material type being measured. If two successive determinations that meet the determinability precision cannot be found for a
sample, suspend execution of this test method for that sample. See Note 7 for further guidance.
13. Cleaning of Viscometer
13.1 Between successive determinations of kinematic viscosity, clean the viscometer thoroughly by several rinsings with the
sample solvent, followed by the drying solvent (see 7.3). Dry the tube by passing a slow stream of filtered dry air through the
viscometer for 2 min or until the last trace of solvent is removed.
13.2 If periodic verification of the viscometer calibration using certified viscosity reference standards (see 9.2) is outside of the
acceptable tolerance band, the viscometer may need to be cleaned. Clean the viscometer with the cleaning solution (Warning—see
7.1), for several hours to remove residual traces of organic deposits, rinse thoroughly with water (7.4) and drying solvent (see 7.3),
and dry with filtered dry air or a vacuum line. Remove any inorganic deposits by hydrochloric acid treatment before the use of
cleaning acid, particularly if the presence of barium salts is suspected. (Warning—It is essential that alkaline cleaning solutions
are not used as changes in the viscometer calibration can occur.)
14. Calculation
14.1 Calculate each of the determined kinematic viscosity values, ν and ν , from the measured flow times, t and t , and the
1 2 1 2
viscometer constant, C, by means of the following equation:
ν 5 C·t (2)
1,2 1,2
where:
ν = determined kinematic viscosity values for ν and ν , respectively, mm /s,
1,2 1 2
2 2
C = calibration constant of the viscometer, mm /s , and
t = measured flow times for t and t , respectively, s.
1,2 1 2
Calculate the kinematic viscosity result, ν, as an average of ν and ν (see 11.2.3 and 12.4.1).
1 2
14.2 Calculate the dynamic viscosity, η, from the calculated kinematic viscosity, ν, and the density, ρ, by means of the following
equation:
η5ν×ρ×10 (3)
where:
η = dynamic viscosity, mPa·s,
ρ = density, kg/m , at the same temperature used for the determination of the kinematic viscosity, and
ν = kinematic viscosity, mm /s.
14.2.1 The density of the sample can be determined at the test temperature of the kinematic viscosity determination by an
appropriate method such as Test Method D1217, D1480, or D1481.
15. Expression of Results
15.1 Report the test results for the kinematic or dynamic viscosity, or both, to four significant figures, together with the test
temperature.
16. Report
16.1 Report the following information:
16.1.1 Type and identification of the product tested,
D445 − 24
16.1.2 Reference to this test method or a corresponding international standard,
16.1.3 Result of the test (see Section 15),
16.1.4 Any deviation, by agreement or otherwise, from the procedure specified,
16.1.5 Date of the test, and
16.1.6 Name and address of the test laboratory.
17. Precision and Bias
17.1 Comparison of Determined Values:
17.1.1 Determinability (d)—The difference between successive determined values obtained by the same operator in the same
laboratory using the same apparatus for a series of operations leading to a single result, would in the long run, in the normal and
correct operation of this test method, exceed the values indicated only in one case in twenty:
Base oils at 40 °C 0.0037 y (0.37 %)
Base oils at 100 °C 0.0036 y (0.36 %)
Formulated oils at 40 °C 0.0037 y (0.37 %)
Formulated oils at 100 °C 0.0036 y (0.36 %)
Formulated oils at 150 °C 0.015 y (1.5 %)
Petroleum wax at 100 °C 0.0080 y (0.80 %)
Residual fuel oils at 50 °C 0.0244 y (2.44 %)
Residual fuel oils at 100 °C 0.03 y (3 %)
15 1.1
Additives at 100 °C 0.00106 y
...