This part of ISO 787 specifies a general method of test for determining the residue on sieve from a sample of pigment or extender dispersed in water.ISO 787-18, General methods of test for pigments and extenders — Part 18: Determination of residue on sieve — Mechanical flushing procedure, specifies a general method of test for determining the residue on sieve from a sample of pigment or extender by a mechanical flushing procedure. For most pigments and extenders, ISO 787-7 and ISO 787-18 will usually give different results, and it is therefore essential to state clearly in a specification which method is to be used and, in the test report, which method has been used.NOTE The general methods given in the various parts of ISO 787 are usually applicable to any pigment or extender. Thus only a cross-reference to the appropriate part of ISO 787 needs to be included in the International Standard giving the specification for that pigment or extender, indicating any detailed modifications that may be needed in view of the special properties of the material in question. Only when the general methods are not applicable to a particular material should a different method for determination of residue on sieve be specified.