ISO/TC 256/WG 3 - General test methods for colorants and extenders

This document specifies the Saunderson correction for different measurement geometries and the solutions of the Kubelka-Munk equation for hiding and transparent layers. It also specifies methods for the calculations of the tinting strength including the residual colour difference based on different criteria such as the depth of shade. Finally, methods for determining the hiding power are provided. The procedures for preparing the samples for these measurements are not part of this document. They are agreed between the contracting parties or are described in other national or international standards.

This document specifies the procedure and test report for determining small colour differences of object colours according to equidistant colour spaces. Three suggestions for metrics for the quantitative determination of small colour differences (∆E Annexes A, B and C. These examples are related to the three colour space models: OSA-UCS modified by Oleari et al., DIN99o and CAM16-UCS (uniform colour space). This document is applicable for the assessment of pigments, dyestuff and extenders in the field of coatings, plastic and prints only that are evaluated in pairs for colour conformity, and which have small perceptible colour differences.

This document specifies different methods of calculating special indices, which are generally used to describe lightness respectively jetness of samples including chroma or hue within one colour-coordinate. This document is applicable to tristimulus values and chromaticity coordinates calculated using colour-matching functions of the standard colorimetric system of the CIE 1931 (2°) or CIE 1964 (10°). It is used for the specification of colour stimuli perceived as belonging to a reflecting or transmitting object where a one-dimensional value is required.

This document specifies a general method of test for determining the mass fraction in percent of matter volatile at a temperature of 105 °C in a sample of pigment or extender. This method is applicable to pigments and extenders that are stable at 105 °C.

This document specifies a formalism for the calculation of the illuminant metamerism of solid surface colours. It cannot be applied to colours of effect coatings without metrical adaptation. This document only covers the phenomenon of metamerism for change of illuminant, which has the greatest meaning in practical application. In the case of chromaticity coordinates of a pair of samples under reference conditions that do not exactly match, recommendations are given on which correction measures are to be taken. Regarding the reproduction of colours, the metamerism index is used as a measure of quality in order to specify tolerances for colour differences between a colour sample and a colour match under different illumination conditions. The quantification of the illuminant metamerism of pairs of samples is formally performed by a colour difference assessment, for which tolerances that are common for the evaluation of residual colour differences can be used. NOTE In the colorimetric literature and textbooks, the term geometric metamerism is sometimes used for the case that two colours appear to be the same under a specific geometry for visual assessment and selected standard observer and standard illuminant pair, but is perceived as two different colours at changed observation geometry. The term geometric metamerism is different to metamerism described in this document.

This document specifies a general method of test for determining the water-soluble nitrates in a sample of pigments by a spectrophotometric method using salicylic acid. ISO 787-13 specifies a method for determining the water-soluble nitrates in a sample of pigments using Nessler`s method.

This document describes a general method of test for comparing the resistance to light of samples of similar types of coloured pigments (agreed reference pigment and test sample). Two methods of exposure are described in this document. In method A, the material is exposed under glass to natural light. In method B, the material is exposed to direct artificial light.

This document specifies a general method of test for determining the water-soluble sulphates, chlorides and nitrates of pigments.

This document specifies a method for determining the total content of polychlorinated biphenyls (PCBs), checking for all 209 possible congeners in pigment materials. This document is applicable to a working range from1 mg/kg to 150 mg/kg. The lower quantitation limit of this method is 1 mg/kg per congener. Results below 1 mg/kg are considered to be qualitative only.

This document specifies a general method of test for comparing the lightening (reducing) power of a white pigment with the lightening power of an agreed sample of the same type. Two procedures (A and B) are specified. Procedure A is quicker than procedure B and is suitable for testing one sample of pigment; procedure B is better for testing several samples, and especially if a pigment of unknown lightening power is being tested.

This document specifies the requirements and the corresponding test methods for three types of lithopone pigments.

This document specifies a general method of test for determining the pH value of an aqueous suspension of a sample of pigment or extender.

This document specifies a general method of test for determining the electric resistivity (specific electric resistance) or the specific electric conductivity, respectively, of the aqueous extract of a pigment. The method is applicable to all pigments and extenders, except pigments that are soluble in water. The resistivity of the aqueous extract of a pigment is considered as a property independent of the amount of water-soluble matter. If agreed, a cold extraction method can be used.

This document specifies a general test method for comparing the colour, in full-shade systems, of white, black or coloured pigments with that of an agreed reference pigment, using a colorimetric procedure.

ISO 18314-1:2015 specifies the method for determining the colour coordinates of a paint film. This method is only applicable to paint films that appear to be uniformly of one colour, i.e. monochromatic, when examined with normal vision. Paint films that do not completely hide a non-transparent substrate represent an opaque system and can be measured by using the procedure in this part of ISO 18314. Luminescent paint films, transparent paint films, and translucent paint films (for example for display or lamp glass), retroreflecting paint films (for example for traffic signs), and metallic paint films are outside the scope of this part of ISO 18314.

ISO 7579:2009 specifies two methods for determining the solubility of dyestuffs in organic solvents. They are applicable to dyestuffs that do not change chemically under the influence of the solvent and are stable and non-volatile under the specified drying conditions. For volatile solvents (boiling point 120 °C), the photometric procedure is recommended. The choice of procedure should be made on a case-by-case basis. The methods are suitable for concentrations between 1 g and 1 000 g of dyestuff per litre of solvent. Higher concentrations can be used provided the viscosity of the solution is such that the procedure can be carried out readily. The methods are not suitable for the determination of insoluble matter in a dyestuff.

ISO 787-7:2009 specifies a general method of test for determining the residue on sieve from a sample of pigment or extender dispersed in water.

Describes common sampling method, expression of results and test report for two methods of density determination using a pyknometer (method A and B) as well as their apparatus and procedure in detail.

The complete procedure consists of four parts: determination of the conditions for the preparation of the dispersion of the coloured pigment, and determination of the ratio of the coloured pigment to white pigment; preparation of the dispersion of the coloured pigment under defined conditions on an automatic muller; mixing the dispersions of coloured pigment and white pigment in a known ratio with a white pigment paste; the strength and undertone of the resulting reduction paste are compared with those of a similar paste made under the same conditions from the agreed reference pigment and the same white pigment paste. - This second edition cancels and replaces the first edition ISO 787/16-1973.

The method specified provide an instrumental alternative to those described in ISO 787/16 and ISO 787/17. Equal masses of a coloured material are separately dispersed in the same mass of the same white pigment paste. The reflectivity of each dispersion is measured photometrically. From the corresponding values of K/S the relative tinting strength is given. For measurement of the relative scattering power equal masses of a white test material and an agreed reference pigment are separately dispersed in the same mass of the same black pigment paste. The reflectivity of each dispersion is measured photometrically at 550 nm. From the corresponding values of K/S the relative scattering power is given.

The method specified can also be applied to the examination of other powders or granules which are insoluble in water. It is neither applicable to hydrophobic nor pelletized materials. In the test apparatus the material under test, dispersed in water, is brought into centrifugal motion by a system of rotating jets of water. he water flushes the fine particles through the sieve, the coarse particles being retained on the sieve. The residue on the sieve is dried and weighed. - Cancels and replaces ISO 787/18-1973 and constitutes its technical revision.

Procedure for comparing the colour of a coloured pigment with that of an agreed sample. The procedures described in this document are acceptable but the method using an automatic muller is the reference method. The binder is not specified. It shall be agreed between the interested parties. If no binder is agreed, linseed oil, complying with the specification in ISO 150, should be used. - Replaces ISO/R 787/1:1968.

The test is carried out by the following procedure: drying of the sample in the oven at (105 2) °C, passing the dried sample through the sieve and transferring it of the graduated measuring cylinder, but so that no air pockets are formed. Weighing of the cylinder and of the sample. Placing of the cylinder in the tamping volumeter and tamping it in steps of approximately 1250 revolutions until the difference between two successive steps of tamping is less than 2 ml. Calculation of results. - Cancels and replaces ISO Recommendation ISO/R 787/11-1970.

The principle of the method consists in the hot extraction of the material by following the procedure specified in ISO 787/3, to the stage of obtaining a perfectly clear filtrate. The determination is carried out with indicator solution (method A). If the solution with the methyl red indicator is yellow (alkaline), titrate it with the hydrochloric acid solution to an orange end-point; if the solution with the methyl red indicator is red (acid), titrate it with the sodium or potassium hydroxide solution to an orange end-point. The other method (method B) is the potentiometric determination. Take 100 ml of the test solution, insert the electrodes of the pH measuring device and read the pH value.

The oil absorption value is required to be compared with the value determined at the same time on an agreed sample of the product. The principle of the method is based on addition of linseed oil from a burette to the test portion. After each addition, rub the oil into the product until conglomerates are formed. Cease the addition of oil when a paste of smooth consistency has been formed. It should just spread without cracking or crumbling. Read the burette and note the quantity of oil used. The result is expressed in millilitres of oil per 100 g of product or in grams of oil per 100 g of product. - Cancels and replaces Part 5 of ISO/R 787-1968.

Specifies a method for comparing the resistance to bleeding with that of an agreed sample. The method has been established because it is essentially a practical test and as such is probably of greater general value than other methods.

The method is intended for comparing the heat stability by specifying the temperatures of heating and the time of heating; it may also be used for determining the heat resistance of a pigment. The comparison of heat stability is carried out against that of an agreed sample.

Displacement liquids of known density should be selected in which the material to be tested is insoluble, and which has good wetting properties and a low evaporation rate under vacuum. High-boiling aromatic or aliphatic hydrocarbons are suitable. The temperature, t, at which the determination is carried out affects the density of the displacement liquid; each weighing should be made at a constant temperature. The principle consists in weighing into a tared tube a quantity of a dried sample, wetting it with displacement liquid, centrifuging until the occluded air is removed and calculation of the density from the difference of masses.

ISO 18314-3:2015 specifies different methods of calculating special indices, which are generally used to describe lightness respectively jetness of samples including chroma or hue within one colour-coordinate. ISO 18314-3:2015 is applicable to tristimulus values and chromaticity coordinates calculated using colour-matching functions of the CIE 1964 standard colourimetric system. It can be used for the specification of colour stimuli perceived as belonging to a reflecting or transmitting object, where a one-dimensional value is required.

ISO 18314-2:2015 specifies the Saunderson correction for different measurement geometries and the solutions of the Kubelka-Munk equation for hiding and transparent layers. It also specifies methods for the calculations of the tinting strength including the residual colour difference with different criteria and of the hiding power. The procedures for preparing the samples for these measurements are not part of this part of ISO 18314. They are agreed between the contracting parties or are described in other national or International Standards.

This part of ISO 787 specifies a general method of test for determining the water-soluble sulfates, chlorides and nitrates of pigments.

This part of ISO 787 specifies a general method of test for determining the resistivity (specific resistance) of the aqueous extract of a pigment. The method is applicable to all pigments and extenders, except pigments that are substantially soluble in water.

This part of ISO 787 specifies a general method of test for comparing the lightening (reducing) power of a white pigment with the lightening power of an agreed sample of the same type. Two procedures (A and B) are described. Procedure A is quicker than procedure B and is suitable for testing one sample of pigment; procedure B is better for testing several samples, and especially if a pigment of unknown lightening power is being tested.

The principle of the method specified is dispersing the test pigment and an agreed reference pigment in a particular test medium (mixture of an alkyd resin and fumed silica), preparing specimens on suitable substrates from the dispersions, measuring the tristimulus values of the specimens as described in ISO 7724-2, calculating the appropriate colour characteristics as described in ISO 7724-3.

Describes two methods of exposure. In method A, the material is exposed under glass to natural light. In method B, the material is exposed to direct artificial light. The test sample and the agreed reference pigment are each dispersed in the same agreed binder. The dispersions are applied to a substrate and dried; they are then exposed to natural daylight with protection from rain (method A) or to artificial light (method B) under specified conditions. The resistance to light is assessed by comparing the change in colour of the test sample to that of the agreed reference pigment. Cancels and replaces the first edition ISO 787/15-1973.

The principle of the method consists in weighing of a test portion and dispersing in a suitable volume of water. The dispersion is poured through a sieve. Washing of the test portion until the washings passing through the sieve are clear and free of dispersed material. Treatment of the residue on the sieve with water and drying in an oven at 105 °C 2 °C. Allow to cool and weigh to the nearest 1 mg. Alternative procedures for the treatment of residue: Washing of the residue into a previously heated and weighed sintered crucible, into a previously heated and weighed 50 ml beaker or into a previously heated and weighed weighing bottle. - Cancels and replaces ISO Recommendation R 787/7-1968.

Specifies a method of test for determining the matter volatile at a temperature of 105 °C in a sample. The procedure is only applicable to materials that are stable at 105 °C. For materials that are unstable at this temperature, the test conditions should be agreed between the interested parties. - Replaces ISO/R 787/2:1968.

The water used shall be freshly distilled water, boiled before use, but for 5 to 10 min only, in order to avoid an increase of its pH value due to alkali dissolved from the glass. Preparation of a suspension of the material under test, stopper the container, shaking, allow to stand any time, removing the stopper and determination, to the nearest 0.1 unit, of the pH value of the suspension. - Cancels and replaces ISO Recommendation R 787/9-1970.