The paint manufacturer must carry out regular and systematic tests on his intermediates and products at various stages of manufacture in order to ensure that uniformity of quality for production is being maintained. The tests of the final product when ready for transfer to containers for issue to customers are of great importance. The tests must show that the product is strictly up to standard both in composition and in the way it behaves when used, i.e. in its 'performance'. The composition may be determined by analysis, while the performance is checked by measuring physical properties of the liquid paint and of the dried film, and especially by trials under conditions reproducing those that will be encountered in practice. The schedule of trials will vary according to the market for which the paint is designed. For example, a coating such as an emulsion paint intended for use over paper or plaster will be tested over these backgrounds and the manufacturer’s instructions will indicate which substrates are suitable. Enamels for metals will be tested on metals following again all the procedures, including metal cleaning and pretreatment, recommended by the manufacturer Amongst some of the more important tests are the following: adhesion, hardness; flexibility, examination of gloss, matching of colour and determination of resistance to the attack of various chemical and mechanical agents and stresses. Where full reproduction of the conditions of use are not possible reliance must be placed on more arbitrarily devised standard tests in which the approved sample and the and hatch-are compared, and if they both respond equally to the tests it is assumed that performance under full scale conditions will be satisfactory.
