Students' Text-Book of Color; Or, Modern Chromatics. with Applications to Art and Industry (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1899 Excerpt: ...that present themselves most frequently is to ascertain the complementary colour of some particular pigment or mixture of pigments. For the rough solution of such questions a method given by Dove.can be employed: A small square of paper, an inch or less in size, is to be painted with the pigment in question and placed on a sheet of black paper, and viewed through an achromatized prism of calc spar. This is shown in Fig. 68, and has the property FtG. 6S.--Achromatic Prism of Cale Spar. of furnishing when held before the eye two equally bright images of objects viewed through it. It is used in this experiment instead of a plain calc-spar prism, because it gives a greater separation of the two images, and thus allows the employment of larger squares of coloured paper. As the finding of the colour which is complementary to any given one depends entirely on experiment, a second piece of paper, also an inch square, is now to be painted with the colour which it is supposed will be complementary to the first, and the two painted papers are to be combined together with the aid of the calc-spar prism. Let us suppose that we wish to obtain the complement of a dull reddish-brown. The red-brown square is placed on the black paper; beside it we lay a piece painted with a dull bluish-green grey, and arrange matters so that an image of the red-brown paper falls on one furnished by the blue-grey paper. If the two colours are complementary, their joint image will be white, or rather pure grey. If, instead of pure grey, it shows a tendency to reddish-grey or bluish-grey, the colour of the second slip of paper must be modified accordingly. This operation is facilitated by constantly comparing the tint obtained with that of a slip of pure grey paper, placed on the same sheet of...