ISO 5267-2:2025
(Main)Pulps — Determination of drainability — Part 2: "Canadian Standard" freeness method
Pulps — Determination of drainability — Part 2: "Canadian Standard" freeness method
This document specifies a method for determination of the drainability of water from a pulp suspension in terms of the “Canadian Standard” freeness method in millilitres. In principle, this method is applicable to all kinds of pulp in aqueous suspension. NOTE Treatments of pulp suspensions which produce a large proportion of fines can induce an anomalous rise in freeness (false freeness), as a rule at values below 100 ml.
Pâtes — Détermination de l'égouttabilité — Partie 2: Méthode de mesure de l'indice d'égouttage "Canadian Standard"
La présente partie de l'ISO 5267 spécifie une méthode de détermination de l'égouttabilité, en termes d'indice d'égouttage «Canadian Standard» (CSF) exprimé en millilitres, d'une suspension aqueuse de pâte. En principe, cette méthode est applicable à tous les types de pâtes en suspension aqueuse. NOTE Les traitements produisant une grande quantité de fines peuvent quelquefois causer des montées anormales d'indice d'égouttage (faux indice), généralement pour des valeurs inférieures à 100 ml.
General Information
Relations
Standards Content (Sample)
International
Standard
ISO 5267-2
Third edition
Pulps — Determination of
2025-10
drainability —
Part 2:
"Canadian Standard" freeness method
Pâtes — Détermination de l'égouttabilité —
Partie 2: Méthode de mesure de l'indice d'égouttage "Canadian
Standard"
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 2
6 Preparation of sample . 2
7 Procedure . 3
8 Expression of results . 3
9 Precision . 4
10 Test report . 4
Annex A (normative) “Canadian Standard” freeness tester . 5
Annex B (normative) Maintenance of the “Canadian Standard” freeness tester .12
Annex C (informative) Freeness corrections to 0,30 % stock concentration .13
Annex D (informative) Freeness corrections to 20 °C .15
Annex E (Informative) Precision . 17
Bibliography .18
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 6, Paper, board and pulps.
This third edition cancels and replaces the second edition (ISO 5267-2:2001), which has been technically
revised.
The main changes are as follows:
— references to a standardizing laboratory and to authorized laboratories, and consequently to ISO 4094,
have been removed to comply with ISO guidelines and ISO 4094 now is only relevant to optical standards;
— some contradictions have been corrected;
— an error in the table in Annex C has been corrected.
A list of all parts in the ISO 5267 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
The “Canadian Standard” freeness test is designed to provide a measure of the rate at which a dilute
suspension of pulp is dewatered under specified conditions. It has been shown that the drainability is
related to the surface conditions and swelling of the fibres, and constitutes a useful index of the amount of
mechanical treatment to which the pulp has been subjected.
The rate at which a suspension dewaters depends on the conditions of measurement, particularly the
geometric characteristics of the instrument. One such instrument is the “Canadian Standard” freeness tester.
The only practical means of achieving the required degree of accuracy for the measurement of “Canadian
Standard” freeness is by the maintenance procedure specified in Annex B and in Annex C. Results of this
test do not necessarily correlate with the drainage behaviour of a fibre suspension on a commercial paper
machine.
A crucial part of the equipment used to determine “Canadian Standard” freeness is the screen plate. When
developing the test, the Pulp and Paper Research Institute of Canada (Paprican) found that even when
screen plates were made to carefully defined specifications, they were variable in performance. A particular
plate was chosen as the ‘standard’ plate and unless the plate used in a “Canadian Standard” freeness tester
matches the performance of this original reference plate the instrument will produce an erroneous result.
Production and calibration of Canadian Freeness Test plates thus requires the existence of an organisation
which maintains a master plate that matches the performance of the original reference plate using a
1)
procedure detailed in this document .
A method for the determination of drainability in terms of the Schopper-Riegler number is specified in
ISO 5267-1.
NOTE Two slightly different types of “Canadian Standard” freeness testers have been in use, as described in
Annex A. These generally provide similar results, although some differences can occur.
1) At the date of publication of this document, FPInnovations, the successor of Paprican, is an organisation that
maintained a master drainage plate using a procedure that meets the requirements detailed in Annex B. This information
is given for the convenience of users of this document and does not constitute an endorsement by ISO.
v
International Standard ISO 5267-2:2025(en)
Pulps — Determination of drainability —
Part 2:
"Canadian Standard" freeness method
1 Scope
This document specifies a method for determination of the drainability of water from a pulp suspension in
terms of the “Canadian Standard” freeness method in millilitres.
In principle, this method is applicable to all kinds of pulp in aqueous suspension.
NOTE Treatments of pulp suspensions which produce a large proportion of fines can induce an anomalous rise in
freeness (false freeness), as a rule at values below 100 ml.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 4119, Pulps — Determination of stock concentration
ISO 4046 (all parts), Paper, board, pulps and related terms — Vocabulary
ISO 5269-1, Pulps — Preparation of laboratory sheets for physical testing — Part 1: Conventional sheet-
former method
ISO 5269-2, Pulps — Preparation of laboratory sheets for physical testing — Part 2: Rapid-Köthen method
ISO 14487, Pulps — Standard water for physical testing
3 Terms and definitions
For the purposes of this document, the terms and definitions given in given in the ISO 4046 series and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
“Canadian Standard” freeness
volume, expressed in millilitres, of the filtrate collected from the side orifice of the “Canadian Standard”
freeness tester with the temperature and stock concentration of the sample within the ranges specified
4 Principle
Drainage through a fibre mat formed during the test on a perforated screen plate of a given volume of an
aqueous pulp suspension into a funnel provided with a bottom and a side orifice. Determination is made of
the volume of filtrate discharged from the side orifice. The volume of the discharged filtrate, in millilitres, is
the “Canadian Standard” freeness of the pulp.
5 Apparatus
The usual laboratory apparatus and the following shall be used.
5.1 “Canadian Standard” freeness tester, which shall be in accordance with Annex A. Instructions for
maintenance of the apparatus given in Annex B shall be followed.
5.2 Sampling cylinder or container, capable of providing a 1 000 ml sample of aqueous suspension with
an error of less than 5 ml.
5.3 Measuring cylinders, calibrated in millilitres and capable of measuring volume with an error less
than 1,0 ml for volumes up to 100 ml, an error less than 2,0 ml for volumes between 100 ml and 250 ml, and
an error less than 5,0 ml for volumes above 250 ml or,
5.4 Tared beaker having sufficient volume to contain the maximum amount of filtrate expected to be
discharged from the side orifice.
5.5 Balance, capable of reading accurately to 0,01 g.
NOTE Although for the determination of the mass of the side orifice discharge a balance of 0,1 g accuracy is
sufficient, for the determination of stock concentration, the necessary accuracy of the balance is 0,01 g.
5.6 Standard water, for physical testing, in accordance with ISO 14487.
6 Preparation of sample
As the drainage of a pulp suspension is affected considerably by dissolved solids and the pH of the water
used in the determination, standard water (5.6) shall be used throughout the test. It is desirable that the
temperature of the standard water is close to the temperature required for the test, i.e. 20,0 °C.
Take sufficient sample of the aqueous suspension of disintegrated pulp to determine its freeness in duplicate,
i.e. containing at least 6 g OD (oven dry) of pulp.
a) If the concentration of the suspension is above 0,32 % and clearly less than 1,2 %, adjust it to
approximately 0,32 % by mass by diluting it using standard water (5.6).
b) If the concentration of the suspension is less than 0,32 %, the suspension shall be thickened to a
concentration between 1,2 % and 1,5 %. As the test result is sensitive to the quantity of fines, or “crill”,
in the suspension the filtrate from the thickening operation shall be recirculated through the pulp pad
until the filtrate is clear.
If the initial stock concentration of the suspension is potentially equal to or above 1,2 % or the suspension
has been thickened using the procedure in b) above, disperse the suspension by treating it in a standard
disintegrator (see ISO 5263-1 or ISO 5263-2 for a description of the disintegrator) at a temperature between
15 °C and 25 °C for 6 000 revolutions of the propeller. Dilute the concentration of the suspension to
approximately 0,32 % using standard water (5.6).
Irrespective of the initial stock concentration, it will now be approximately 0,32 %. Determine the actual
stock concentration in accordance with ISO 4119. Dilute the suspension to a stock concentration of
0,30 % ± 0,01 % by mass and adjust the temperature to 20,0 °C ± 0,5 °C (see the Note). Throughout the
preparation of the sample, take care to avoid the formation of air bubbles in the suspension.
If there is a delay of more than 30 min between sampling and testing, the freeness of the suspension can
change. In this case the suspension shall be deemed to have a concentration less than 0,32 % and shall be
treated as described above.
NOTE In some applications, e.g. process control, larger deviations than 0,01 % for stock concentration and 0,5 °C
for temperature are often accepted but deviations in stock concentration and temperature usually affect the result.
The “Canadian Standard” freeness is commonly corrected with the aid of correction tables given in informative
Tables C.1 and D.1. These tables were developed from groundwood freeness evaluation studies and their accuracy for
chemical pulps has not been determined. The result so obtained does not conform to this document.
7 Procedure
Check that the funnel and drainage chamber of the “Canadian Standard” freeness apparatus (5.1) are
thoroughly clean. Place the drainage chamber in position. Rinse the chamber and funnel with standard
water ensuring that they are well wetted and the temperature of the apparatus is at 20,0 °C ± 0,5 °C.
Place the measuring cylinder or tared beaker (5.3 or 5.4) in position to receive the discharge from the side
orifice.
Whilst stirring, transfer 1 000 ml ± 5 ml of homogeneous pulp suspension to a clean sampling cylinder or
container (5.2).
Close the bottom of the chamber of the freeness tester and open the top lid and the air-cock.
Mix the sample by closing the top of the cylinder or container with the hand and invert the cylinder or
container (5.2) through 180° three times, without losing any stock. As far as possible, avoid introducing air
into the stock at this stage.
Pour the stock gently but as rapidly as possible into the drainage chamber. At the end of the pouring, the
stock should be almost motionless in the chamber. This can be achieved by pouring the stock around the
inside of the chamber and finishing the pouring in the centre. Immediately close the top lid and the air-cock
and open the bottom lid. Allow 5 s to elapse from the time of opening the bottom lid, then open the air-cock
in a single motion to start the flow.
When the discharge from the side orifice has stopped, read the volume of this discharge to the nearest 1 ml
for values below 100 ml, to the nearest 2 ml for values between 100 ml and 250 ml, and to the nearest 5 ml
for values exceeding 250 ml. For greater accuracy, use the tared beaker and weigh it and its contents to the
nearest 0,1 g. Convert the mass of the contents to volume (ml).
Combine, in a 2 000 ml beaker, the pulp from the chamber, side orifice discharge and bottom orifice discharge
and drain the slurry in a sheet machine in accordance with ISO 5269-1 or ISO 5269-2, using the normal wire
or a suitable filter paper. For pulps with a high fines content, it is recommended to drain the pulp slurry on
a tared filter paper in a Buchner funnel. Oven-dry the pad to a constant mass and record it to the nearest
0,01 g. Use this mass to calculate the stock concentration. If the concentration is not within the specified
range, the determination shall be repeated.
Carry out the determination in duplicate. If the duplicate determinations differ by more than 2 % from their
mean value they shall be repeated.
After each test, the chamber and funnel shall be rinsed out with clean water to ensure that there is no
accumulation of pulp. It is particularly necessary to ensure that no pulp is retained in the holes of the screen
plate. If pitch, oil or grease may have contaminated the equipment, it shall be thoroughly cleaned to remove
such contaminants.
8 Expression of results
Report the mean of the two valid determinations as the “Canadian Standard” freeness in ml.
9 Precision
The repeatability of this method was determined from two studies. Details of the samples used and the
results are presented in Annex E. Reliable reproducibility data is not available.
10 Test report
The test report shall include the following particulars:
a) reference to this document, i.e. ISO 5267-2:2025;
b) date and place of testing;
c) all information necessary for identification of the sample tested;
d) the mean result in ml;
e) the type of funnel used in the test (modified or original design);
f) any unusual features observed during the test;
g) any operations not specified in this document or in the International Standard to which reference is
made or regarded as optional, which might have affected the results.
Annex A
(normative)
“Canadian Standard” freeness tester
A.1 “Canadian Standard” freeness tester
The tester comprises a drainage chamber and a rate-measuring funnel, mounted on a suitable support
(see Figure A.1). The rate-measuring funnel shown in Figure A.1, represents a modified design, adopted
by the Canadian Pulp and Paper Association Technical Section as a standard in 1964. The original design
side orifice, with the angle cut, fulfils the requirement of this standard. Work carried out at Pulp and Paper
Research Institute of Canada (Paprican) in 1993 comparing the two funnel designs shown in Figure A.2,
using chemical pulps ranging in Canadian Standard freeness from 215 ml to 696 ml, showed no difference in
results between the two funnels.
The dimensional and flow specifications given below are those required for the modified instrument to
provide freeness results that are in complete agreement with those obtained from the original Canadian
Standard freeness tester design. Test equipment made to the original design (without the centred side orifice
or volume adjusting plug) may require adjustment to somewhat different values for calibration, and these
values should be stated by the manufacturer. Where careful calibration procedures are followed, Canadian
Standard freeness results, from either tester design, can be made to agree within the limits prescribed in A.5.
The calibration of the rate-measuring funnel requires that two critical dimensions be adjusted within
specified limits:
a) the head of water in the funnel, which influences the flow through the bottom orifice;
b) the volume of water in the bottom section, from the bottom of the cone to the side orifice overflow level,
given as 23,5 ml in the standard procedure.
In this procedure the side orifice position is adjusted to provide the required volume, and early funnels in
which the head above the bottom orifice falls within the specification are acceptable. No adjustment shall be
made after the initial calibration.
NOTE This caused occasional rejection of funnels which did not meet both requirements. It was also demonstrated
that, with the side orifice tube cut at an angle to the tube axis, variation in the flow of water from the side orifice could
result when the funnel was rotated through 180° and the tester was not perfectly level. The design that was adopted
in 1964 utilises a side orifice tube which is cut at 90° to the tube axis, and which is mounted so that the overflow from
the funnel occurs at
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