The Chemistry Of Paints And Paint Vehicles PDF Download

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1906 edition. Excerpt: ... CHAPTER III THE ANALYSIS OF DRY COLORS, PASTES, AND LIQUID PAINTS Treatment of Sample. -- In case of pastes and liquid paints take enough of the sample to permit of all necessary future tests and for analysis, put it in a suitable glass and add benzine. In the case of colors in japan and varnish, first wash thoroughly with turpentine before adding benzine, as the latter is liable to precipitate any gums present on the pigment, in which case they will not redissolve. (The turpentine should be added slowly with constant stirring.) Set the sample aside and let settle until the benzine is clear, then decant, adding fresh benzine and repeating until the color is free from oil. The color should be allowed to settle completely before the benzine is decanted, otherwise some of the lighter materials which do not settle readily may be lost, and thus the sample finally obtained will not represent the true proportions of constituents. Dry the sample in an air oven, grind with a spatula on a rough filter paper until it is thoroughly homogenous and pulverized. If it is properly washed and not dried too long it readily forms a fine powder. If any particles of dried oil or skin are observed, pass the sample through an 80-mesh sieve. This, however, should be avoided as much as possible by taking the sample of paste from below the surface, if the surface is at all dried. Some chemists make a practice of using a centrifugal machine in separating the color from the naphtha, but this will not be found so convenient as the above method. Where great haste is desired this plan has its advantages, but the author finds that by using a vessel for washing of sufficient size, only two washings are necessary to free the pigment from oil, and ordinarily this may be...