ASTM D6131-17(2023)

Standard Test Method for Evaluating the Relative Tint Undertone of Titanium Dioxide Pigments

SIGNIFICANCE AND USE
5.1 This test method allows the user to make a determination of the blueness or yellowness of the tint undertone of titanium dioxide pigments, versus a reference pigment agreed upon by the parties to the test. This is an important measure of tone, since it gives both a measure of effective particle size, and quick approximation of the blue/yellow undertone that can be expected when a coating containing the titanium dioxide is tinted.  
5.2 Such matters as the vehicle for preparing the dispersions and the mechanical method of preparing the dispersion are left to the user. However, variation in these practices will lead to increased variance in the results, so users ought to fix these parameters, in-so-far as is possible, within any one laboratory. This will lead to reduced uncertainty of the results within that laboratory, and it is seldom that interlaboratory comparisons of this test result is needed.  
5.3 Each user must decide whether the loss of accuracy in his measurements due to variation of these parameters is negligibly small for the purpose for which the data are obtained.
SCOPE
1.1 This test method is intended to be used to determine the tint undertone (blue or yellow) of titanium dioxide pigments. This relates to the effective particle size of the pigment  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 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.  
1.4 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: 30-Jun-2023
• ICS: 87.060.10 - Pigments and extenders
• Technical Committee: D01 - Paint and Related Coatings, Materials, and Applications
• Drafting Committee: D01.26 - Optical Properties

Relations

• Refers: ASTM D16-24 - Standard Terminology for Paint, Related Coatings, Materials, and Applications
• Effective Date: 01-Jan-2024
• Refers: ASTM E1331-15(2023) - Standard Test Method for Reflectance Factor and Color by Spectrophotometry Using Hemispherical Geometry
• Effective Date: 01-Nov-2023
• Refers: ASTM E1164-23 - Standard Practice for Obtaining Spectrometric Data for Object-Color Evaluation
• Effective Date: 01-Nov-2023
• Refers: ASTM E1347-06(2020) - Standard Test Method for Color and Color-Difference Measurement by Tristimulus Colorimetry
• Effective Date: 01-May-2020
• Refers: ASTM E1331-15(2019) - Standard Test Method for Reflectance Factor and Color by Spectrophotometry Using Hemispherical Geometry
• Effective Date: 01-Nov-2019
• Refers: ASTM E308-17 - Standard Practice for Computing the Colors of Objects by Using the CIE System
• Effective Date: 01-May-2017
• Refers: ASTM D16-16 - Standard Terminology for Paint, Related Coatings, Materials, and Applications
• Effective Date: 01-Jul-2016
• Refers: ASTM E1347-06(2015) - Standard Test Method for Color and Color-Difference Measurement by Tristimulus Colorimetry
• Effective Date: 01-Nov-2015
• Refers: ASTM E1331-15 - Standard Test Method for Reflectance Factor and Color by Spectrophotometry Using Hemispherical Geometry
• Effective Date: 01-Jul-2015
• Refers: ASTM E308-15 - Standard Practice for Computing the Colors of Objects by Using the CIE System
• Effective Date: 01-Apr-2015
• Refers: ASTM D16-14 - Standard Terminology for Paint, Related Coatings, Materials, and Applications
• Effective Date: 01-Dec-2014
• Refers: ASTM E1349-06(2013) - Standard Test Method for Reflectance Factor and Color by Spectrophotometry Using Bidirectional (45°:0° or 0°:45°) Geometry
• Effective Date: 01-Jan-2013
• Refers: ASTM D16-12 - Standard Terminology for Paint, Related Coatings, Materials, and Applications
• Effective Date: 01-Aug-2012
• Refers: ASTM E308-12 - Standard Practice for Computing the Colors of Objects by Using the CIE System
• Effective Date: 01-Jul-2012
• Refers: ASTM E1164-12e1 - Standard Practice for Obtaining Spectrometric Data for Object-Color Evaluation
• Effective Date: 01-Jul-2012

Overview

ASTM D6131-17(2023) is the internationally recognized standard test method for evaluating the relative tint undertone of titanium dioxide pigments. Developed by ASTM International, this test method is essential for quantifying whether the tint undertone of titanium dioxide is more blue or yellow relative to a reference pigment. The tint undertone determination is closely connected to the effective particle size of the pigment, providing valuable insights for manufacturers and users in the coatings, paints, and plastics industries.

The procedure described ensures accurate assessment by dispersing the pigment in a chosen medium, applying the resulting mixture on standardized drawdown cards, and measuring colorimetric values with calibrated instruments. This standard supports product development, quality assurance, and internal process optimization in laboratories that work with titanium dioxide pigments.

Key Topics

• Tint Undertone Determination: The core of ASTM D6131-17(2023) is the measurement of the blueness or yellowness of titanium dioxide pigments relative to an agreed-upon reference. This is often described by calculating the Yellowness Index (YI) from instrumental readings.
• Relevance to Particle Size: The undertone result reflects the effective particle size of the pigment, which can influence the appearance and performance of coatings and colored products.
• Test Procedure Highlights:
  • Preparation of pigment dispersions according to the user’s end-use scenario.
  • Application of pigment mixtures to black and white sealed drawdown cards.
  • Measurement with colorimetric spectrophotometers or tristimulus colorimeters in the specified spectral range (400-700 nm).
• Reporting Requirements: The standard specifies the necessary data to report, including pigment type, reference standard, pigment-to-vehicle ratio, instrument details, tristimulus values, and the calculated yellowness index.
• Precision and Laboratory Control: Users are advised to standardize dispersion vehicles and methods within their laboratory to minimize measurement variance, as interlaboratory comparisons are uncommon for this method.

Applications

ASTM D6131-17(2023) is widely applied in:

• Paints and Coatings: Ensuring color consistency and desired undertone when formulating paints and industrial coatings that contain titanium dioxide pigments.
• Plastics Manufacturing: Assessing pigment undertone helps achieve the correct shade and opacity in plastic products.
• Quality Control: Labs utilize this method to monitor batch-to-batch consistency, verify pigment supplier claims, and support regulatory documentation.
• Research and Product Development: Technologists use undertone evaluation results to optimize pigment formulations for new product innovations.
• Internal Laboratory References: Many organizations use this method for internal benchmarking rather than for formal interlaboratory comparison.

Related Standards

This ASTM standard is complemented by a series of related references that support colorimetric testing and terminology:

• ASTM D16 - Terminology for Paint, Related Coatings, Materials, and Applications
• ASTM E308 - Practice for Computing the Colors of Objects by Using the CIE System
• ASTM E1164 - Practice for Obtaining Spectrometric Data for Object-Color Evaluation
• ASTM E1331 - Test Method for Reflectance Factor and Color by Spectrophotometry Using Hemispherical Geometry
• ASTM E1347 - Test Method for Color and Color-Difference Measurement by Tristimulus Colorimetry
• ASTM E1349 - Test Method for Reflectance Factor and Color by Spectrophotometry Using Bidirectional Geometry

These standards provide guidance on procedures, instruments, and colorimetric data interpretation to ensure consistency and reliability in tint undertone evaluations of titanium dioxide pigments.

Keywords: ASTM D6131, titanium dioxide, tint undertone, pigment evaluation, yellowness index, blue undertone, quality control, color measurement, paint pigments, pigment characterization.

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: D6131 − 17 (Reapproved 2023)
Standard Test Method for
Evaluating the Relative Tint Undertone of Titanium Dioxide
Pigments
This standard is issued under the fixed designation D6131; 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.
1. Scope Spectrophotometry Using Bidirectional (45°:0° or 0°:45°)
Geometry
1.1 This test method is intended to be used to determine the
tint undertone (blue or yellow) of titanium dioxide pigments.
3. Terminology
This relates to the effective particle size of the pigment
3.1 Any special terms used in this test method can be found
1.2 The values stated in SI units are to be regarded as
in Terminology D16.
standard. No other units of measurement are included in this
4. Summary of Test Method
standard.
1.3 This standard does not purport to address all of the 4.1 Titanium dioxide pigments are dispersed in a liquid
safety concerns, if any, associated with its use. It is the medium of the user’s choice by a dispersion method applicable
responsibility of the user of this standard to establish appro- to the user’s intended end use. Test and reference pigments are
priate safety, health, and environmental practices and deter- treated identically. The resultant white paints or colorants are
mine the applicability of regulatory limitations prior to use. drawn down on white and black cards and read instrumentally.
1.4 This international standard was developed in accor- These readings are then used to calculate the yellowness index.
dance with internationally recognized principles on standard-
5. Significance and Use
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- 5.1 This test method allows the user to make a determina-
tion of the blueness or yellowness of the tint undertone of
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee. titanium dioxide pigments, versus a reference pigment agreed
upon by the parties to the test. This is an important measure of
2. Referenced Documents
tone, since it gives both a measure of effective particle size, and
quick approximation of the blue/yellow undertone that can be
2.1 ASTM Standards:
expected when a coating containing the titanium dioxide is
D16 Terminology for Paint, Related Coatings, Materials, and
tinted.
Applications
E308 Practice for Computing the Colors of Objects by Using
5.2 Such matters as the vehicle for preparing the dispersions
the CIE System
and the mechanical method of preparing the dispersion are left
E1164 Practice for Obtaining Spectrometric Data for Object-
to the user. However, variation in these practices will lead to
Color Evaluation
increased variance in the results, so users ought to fix these
E1331 Test Method for Reflectance Factor and Color by
parameters, in-so-far as is possible, within any one laboratory.
Spectrophotometry Using Hemispherical Geometry
This will lead to reduced uncertainty of the results within that
E1347 Test Method for Color and Color-Difference Mea-
laboratory, and it is seldom that interlaboratory comparisons of
surement by Tristimulus Colorimetry
this test result is needed.
E1349 Test Method for Reflectance Factor and Color by
5.3 Each user must decide whether the loss of accuracy in
his measurements due to variation of these parameters is
negligibly small for the purpose for which the data are
This test method is under the jurisdiction of ASTM Committee D01 on Paint
and Related Coatings, Materials, and Applications and is the direct responsibility of obtained.
Subcommittee D01.26 on Optical Properties.
Current edition approved July 1, 2023. Published August 2023. Originally 6. Apparatus
approved in 1997. Last previous edition approved in 2017 as D6131 – 17. DOI:
6.1 Balance, electronic scale with readability of 0.01 g and
10.1520/D6131-17R23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or resolution of 0.02 g.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
6.2 Drawdown Cards, black and white sealed drawdown
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. charts.
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D6131 − 17 (2023)
6.3 Drawdown Bars, capable of applying a coating typically 100 1.0313 X 2 1.14
...