History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c20.s3.1

v1.c20.s3.1

Pigments are insoluble substances used to give colour or tint to paint and other surface coatings. It is generally distinguished from dye which is soluble and penetrates the tissues of fibres of any organic material (Newman, Vol.I). Pigments contribute to the optical and other properties of paints, finishes and coatings. Pigments for paint should be insoluble in their vehicle and chemically inert to it. They should have good covering or spreading power and clean intense colours. Since they are insoluble in the coating material, they are mechanically mixed with the coating and are deposited when the coating dries up. Their physical properties are not changed by incorporation in and deposition from the vehicle. Pigments may be classified according to composition as organic or inorganic or by source as natural or synthetic. Generally, for all practical purposes the classification may be done by colour or by function (McGraw-Hill, Vol-4). Since the pre-historic days, pigments were used in preparing slips and paints for potteries, for artistic paintings of pictures and portraits, for coating surfaces and walls etc.