ISO/DIS 787-29:2026(en)

ISO/TC 256

Secretariat: DIN

Date: 2026-01-27

General methods of test for pigments and extenders — Part 29: determination of resistance to liquids

© ISO 2026

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Contents

Foreword iv

1 Scope 1

2 Normative references 1

3 Terms and definitions 1

4 Apparatus 2

5 Reagents and materials 2

6 Sampling 2

7 Resistance to water 2

7.1 Procedure 2

7.1.1 Number of determinations 2

7.1.2 Preparation of filtrate 3

7.1.3 Assessment of staining grade 3

7.2 expression of results 3

8 Resistance to acid 3

8.1 Procedure 3

8.1.1 Number of determinations 3

8.1.2 Preparation of filtrate and filter cake 3

8.1.3 Assessment of staining grade 4

8.1.4 Assessment of colour change grade 4

8.2 Expression of results 4

9 Resistance to alkali 5

9.1 Procedure 5

9.1.1 Number of determinations 5

9.1.2 Preparation of filtrate and filter cake 5

9.1.3 Assessment of staining grade 5

9.1.4 Assessment of colour change grade 5

9.2 Expression of results 5

10 Resistance to solvent 6

10.1 Procedure 6

10.1.1 Number of determinations 6

10.1.2 Preparation of filtrate 6

10.1.3 Assessment of staining grade 6

10.2 Expression of results 6

11 Test report 7

Bibliography 8

Foreword

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General methods of test for pigments and extenders — Part 29: determination of resistance to liquids

This document specifies general test methods for determining the resistance to water, acid, alkali-and solvent of pigments.

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 105‑A02, Textiles — Tests for colour fastness — Part A02: Grey scale for assessing change in colour

ISO 105‑A03, Textiles — Tests for colour fastness — Part A03: Grey scale for assessing staining

ISO 105‑A04, Textiles — Tests for colour fastness — Part A04: Method for the instrumental assessment of the degree of staining of adjacent fabrics

ISO 105‑A05, Textiles — Tests for colour fastness — Part A05: Instrumental assessment of change in colour for determination of grey scale rating

ISO 3696, Water for analytical laboratory use — Specification and test methods

ISO 15528, Paints, varnishes and raw materials for paints and varnishes — Sampling

CIE 15:2018, Colorimetry

For the purposes of this document, the following terms and definitions 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

resistance to water

the ability of the pigment to resist the dissolution in water and the staining to water

3.2

resistance to acid

the ability of the pigment to resist the staining to the acid solution and the colour change of the pigment by the action of acid and dissolution of pigment in acid

3.3

resistance to alkali

the ability of the pigment to resist the staining to the alkali solution and the colour change of the pigment by the action of alkali and dissolution of pigment in alkali

3.4

resistance to solvent

the ability of the pigment to resist the dissolution in the solvent and the staining to solvent

Use ordinary laboratory apparatus and glassware, together with the following:

4.1 Glass container, made of chemically resistant glass, of capacity 25 ml, fitted with a ground stopper.

4.2 Mechanical shaker, providing movement to obtain a sufficient contact between pigment sample and liquid with the amplitudes of to-and-from 30 mm to 50 mm at a rate of 280 min⁻¹.

4.3 Vacuum filtration system, fitted with a filter funnel of capacity 25 ml and a filter flask of capacity 125 ml.

4.4 Filter paper, fine textured.

4.5 Cuvette, 5 mm light path length.

4.6 Cuvette holder, with white background and two holes suitable for the cuvettes.

4.7 Grey scale for assessing change in colour, complying with the requirements of ISO 105-A02.

4.8 Grey scale for assessing staining, complying with the requirements of ISO 105-A03.

4.9 Spectrophotometer or colorimeter, meeting any one of the geometric conditions for reflection and transmission measurements described in CIE 15:2018.

4.10 Balance, accurate to 0,001 g or better.

4.11 Glass slide, clear and colourless, with suitable size.

Use only reagents of recognized chemically grade and only water of at least grade 3 purity as specified in ISO 3696.

5.1 Hydrochloric acid solution, CAS Registry Number^®[1] 7647-01-0, 2 % (mass fraction) or to be agreed between the interested parties.

5.2 Sodium hydroxide solution, CAS Registry Number^®1 1310-73-2, 2 % (mass fraction) or to be agreed between the interested parties.

5.3 Solvent, to be agreed between the interested parties.

Take a representative sample of the product to be tested, in accordance with ISO 15528.

Carry out all tests in duplicate.

Preparation with cold water

Weigh, to the nearest 1 mg, 0,5 g of pigment sample into the glass container (4.1), add 20 ml of distilled water, cover with the ground stopper tightly. Fix the glass container horizontally on the mechanical shaker (4.2) or shake violently by hand for 5 min, and then stand for 30 min. Transfer the suspension into the filter funnel of a vacuum filtration system (4.3) paved with three layers of filter paper (4.4) and filter in vacuum until clear filtrate is obtained.

Preparation with hot water

Weigh 0,5 g of pigment sample, to the nearest 1 mg, into the glass container (4.1), add 20 ml of boiling distilled water, cover with the ground stopper tightly. After the sample is wetted fully, heat the glass container in a boiling water bath for 10 min, then cool it to room temperature. Transfer the suspension into the filter funnel of a vacuum filtration system (4.3) paved with three layers of filter paper (4.4), and filter in vacuum until a clear filtrate is obtained.

Visual assessment

Fill two cuvettes (4.5) respectively with distilled water and the clear filtrate prepared according to 7.1.2.1 or 7.1.2.2, and insert these two cuvettes into the cuvette holder (4.6). Illuminate the surfaces with north sky light in the Northern hemisphere, south sky light in the Southern hemisphere, or an equivalent source with an illumination of 600 lx or more. The light should be incident upon the surfaces at approximately 45° and the direction of viewing approximately perpendicular to the plane of the surfaces. Compare the visual difference between the distilled water and the filtrate with the differences represented by the grey scale for assessing staining (4.8).

Instrumental assessment

Fill two cuvettes (4.5) respectively with distilled water and the clear filtrate prepared according to 7.1.2.1 or 7.1.2.2. Measure the colour values of distilled water in the cuvette and the colour values of the clear filtrate in the cuvette respectively with spectrophotometer or colorimeter (4.9) using CIE standard illuminant D65 and 10° observer. Calculate the CIELAB L*, a*, b* values. Determine the staining-scale rating (SSR) as described in ISO 105-A04.

The resistance of pigment to water is expressed by the staining rating of the pigment filtrate.

A 9-step scale is used to express the result. The best staining rating of the filtrate is 5 and the worst is 1. The half-step staining ratings are expressed as 4-5, 3-4, 2-3 and 1-2.

If the parallel test results do not match, the differences being more than half-step rating, repeat the test, if necessary, record all the results.

Carry out all tests in duplicate.

Weigh two pigment samples, each 0,5 g, to the nearest 1 mg, into glass containers (4.1) respectively. Add 20 ml distilled water to one container, and add 20 ml hydrochloric acid solution (5.1) to the other. Cover the two containers with ground stoppers tightly, and fix them horizontally on the mechanical shaker (4.2) or shake violently by hand for 5 min. Transfer each suspension into a filter funnel of a vacuum filtration system (4.3) paved with three layers of filter paper (4.4) and filter in vacuum until clear filtrate is obtained. Retain the filter cakes as well.

Visual assessment

Fill two cuvettes (4.5) respectively with hydrochloric acid solution (5.1) and the clear filtrate prepared by hydrochloric acid solution according to 8.1.2, and insert these two cuvettes into the cuvette holder (4.6). Illuminate the surfaces with north sky light in the Northern hemisphere, south sky light in the Southern hemisphere, or an equivalent source with an illumination of 600 lx or more. The light should be incident upon the surfaces at approximately 45° and the direction of viewing approximately perpendicular to the plane of the surfaces. Compare the visual difference between the hydrochloric acid solution and the filtrate with the differences represented by the grey scale for assessing staining (4.8).

Instrumental assessment

Fill two cuvettes (4.5) respectively with hydrochloric acid solution (5.1) and the clear filtrate prepared by hydrochloric acid solution according to 8.1.2. Measure the colour values of hydrochloric acid solution in the cuvette and the colour values of the clear filtrate in the cuvette respectively with spectrophotometer or colorimeter (4.9) using CIE standard illuminant D65 and 10° observer. Calculate the CIELAB L*, a*, b* values. Determine the staining-scale rating (SSR) as described in ISO 105-A04.

Visual assessment

Place two filter cakes prepared according to 8.1.2 on the white ceramic plate in parallel, pressed with a glass slide (4.11). Illuminate the surfaces with north sky light in the Northern hemisphere, south sky light in the Southern hemisphere, or an equivalent source with an illumination of 600 lx or more. The light should be incident upon the surfaces at approximately 45° and the direction of viewing approximately perpendicular to the plane of the surfaces. Compare the visual difference between these two filter cakes with the differences represented by the grey scale for assessing change in colour (4.7).

Instrumental assessment

Press two filter cakes prepared according to 8.1.2 with a glass slide (4.11) to flatten the surface. Measure the colour values of these two filter cakes respectively with spectrophotometer or colorimeter (4.9) using CIE standard illuminant D65 and 10° observer. Calculate the CIELAB L*, C_ab*, h_ab* values. Determine the grey scale rating for colour change (GS_C) as described in ISO 105-A05.

The resistance of pigment to acid is expressed by the staining rating of the pigment filtrate, the colour change rating of the filter cake, or both of them.

A 9-step scale is used to express the result. The best staining rating of the filtrate is 5 and the worst is 1. The half-step staining ratings are expressed as 4-5, 3-4, 2-3 and 1-2. Similarly, the best colour change rating of the filter cake is 5 and the worst is 1. The half-step colour change ratings are expressed as 4-5, 3-4, 2-3 and 1-2.

The result comprising both the staining rating of the filtrate and the colour change rating of the filter cake shall be expressed as indicated in the following example:

— 5[4-5]

This means a staining rating of the filtrate is 5 and a colour change rating of the filter cake is 4-5.

If the parallel test results do not match, the differences being more than half-step rating, repeat the test, if necessary, record all the results.

Carry out all tests in duplicate.

Weigh two pigment samples, each 0,5 g, to the nearest 1 mg, into two glass containers (4.1) respectively. Add 20 ml distilled water to one container, and add 20 ml sodium hydroxide solution (5.2) to the other. Cover the two containers with ground stoppers tightly, and fix them horizontally on the mechanical shaker (4.2) or shake violently by hand for 5 min. Transfer each suspension into a filter funnel of a vacuum filtration system (4.3) paved with three layers of filter paper (4.4) and filter in vacuum until clear filtrate is obtained. Retain the filter cakes as well.

Visual assessment

Fill two cuvettes (4.5) respectively with sodium hydroxide solution (5.2) and the clear filtrate prepared by sodium hydroxide solution according to 9.1.2, and insert these two cuvettes into the cuvette holder (4.6). Illuminate the surfaces with north sky light in the Northern hemisphere, south sky light in the Southern hemisphere, or an equivalent source with an illumination of 600 lx or more. The light should be incident upon the surfaces at approximately 45° and the direction of viewing approximately perpendicular to the plane of the surfaces. Compare the visual difference between the sodium hydroxide solution and the filtrate with the differences represented by the grey scale for assessing staining (4.8).

Instrumental assessment

Fill two cuvettes (4.5) respectively with sodium hydroxide solution (5.2) and the clear filtrate prepared by sodium hydroxide solution according to 9.1.2. Measure the colour values of sodium hydroxide solution in the cuvette and the colour values of the clear filtrate in the cuvette respectively with spectrophotometer or colorimeter (4.9) using CIE standard illuminant D65 and 10° observer. Calculate the CIELAB L*, a*, b* values. Determine the staining-scale rating (SSR) as described in ISO 105-A04.

Visual assessment

Place two filter cakes prepared according to 9.1.2 on the white ceramic plate in parallel, pressed with a glass slide (4.11). Illuminate the surfaces with north sky light in the Northern hemisphere, south sky light in the Southern hemisphere, or an equivalent source with an illumination of 600 lx or more. The light should be incident upon the surfaces at approximately 45° and the direction of viewing approximately perpendicular to the plane of the surfaces. Compare the visual difference between these two filter cakes with the differences represented by the grey scale for assessing change in colour (4.7).

Instrumental assessment

Press two filter cakes prepared according to 9.1.2 with a glass slide (4.11) to flatten the surface. Measure the colour values of these two filter cakes respectively with spectrophotometer or colorimeter (4.9) using CIE standard illuminant D65 and 10° observer. Calculate the CIELAB L*, C_ab*, h_ab* values. Determine the grey scale rating for colour change (GS_C) as described in ISO 105-A05.

The resistance of pigment to alkali is expressed by the staining rating of the pigment filtrate, the colour change rating of the filter cake, or both of them.

A 9-step scale is used to express the result. The best staining rating of the filtrate is 5 and the worst is 1. The half-step staining ratings are expressed as 4-5, 3-4, 2-3 and 1-2. Similarly, the best colour change rating of the filter cake is 5 and the worst is 1. The half-step colour change ratings are expressed as 4-5, 3-4, 2-3 and 1-2.

The result comprising both the staining rating of the filtrate and the colour change rating of the filter cake shall be expressed as indicated in the following example:

— 5[4-5]

This means a staining rating of the filtrate is 5 and a colour change rating of the filter cake is 4-5.

If the parallel test results do not match, the differences being more than half-step rating, repeat the test, if necessary, record all the results.

Carry out all tests in duplicate.

Weigh, to the nearest 1 mg, 0,5 g of pigment sample into the glass container (4.1), add 20 ml of agreed solvent (5.3), cover with the ground stopper tightly. Fix the glass container horizontally on the mechanical shaker (4.2) or shake violently by hand for 5 min. Transfer the suspension into the filter funnel of a vacuum filtration system (4.3) paved with three layers of filter paper (4.4) and filter in vacuum until clear filtrate is obtained.

Visual assessment

Fill two cuvettes (4.5) respectively with the agreed solvent (5.3) and the clear filtrate prepared according to 10.1.2, and insert these two cuvettes into the cuvette holder (4.6). Illuminate the surfaces with north sky light in the Northern hemisphere, south sky light in the Southern hemisphere, or an equivalent source with an illumination of 600 lx or more. The light should be incident upon the surfaces at approximately 45° and the direction of viewing approximately perpendicular to the plane of the surfaces. Compare the visual difference between the agreed solvent and the filtrate with the differences represented by the grey scale for assessing staining (4.8).

Instrumental assessment

Fill two cuvettes (4.5) respectively with the agreed solvent (5.3) and the clear filtrate prepared according to 10.1.2. Measure the colour values of the agreed solvent in the cuvette and the colour values of the clear filtrate in the cuvette respectively using CIE standard illuminant D65 and 10° observer. Calculate the CIELAB L*, a*, b* values. Determine the staining-scale rating (SSR) as described in ISO 105-A04.

The resistance of pigment to solvent is expressed by the staining rating of the pigment filtrate.

A 9-step scale is used to express the result. The best staining rating of the filtrate is 5 and the worst is 1. The half-step staining ratings are expressed as 4-5, 3-4, 2-3 and 1-2.

If the parallel test results do not match, the differences being more than half-step rating, repeat the test, if necessary, record all the results.

The test report shall contain at least the following information:

a) all details necessary to identify the product tested;

b) a reference to this document, i.e. ISO 787-29:—;

c) whether cold water or hot water was used for the test of resistance to water;

d) the solvent used for the test of resistance to solvent;

e) any deviation, by agreement or otherwise, from the test method specified;

f) any unusual features (anomalies) observed during the test;

g) the results of the test;

h) the date of the test.

Bibliography

[1] GB/T 5211.5:2008, Method for the determination of resistance to materials of pigments

1. Chemical Abstracts Service (CAS) Registry Number® is a trademark of the American Chemical Society (ACS). This information is given for the convenience of users of this document and does not constitute an endorsement by ISO of the product named. Equivalent products may be used if they can be shown to lead to the same results. ↑