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CHAPTER XX PRINTING FROM SCREEN-PLATES
The comparative ease with which a color result can be obtained with screen-plates, and the obvious disadvantage that for every copy desired it is essential to make a fresh exposure, naturally led to attempts to duplicate them by copying or printing, but there are unfortunately several pitfalls.
C. E. K. Mees1 (p. 562), put the matter in a very simple and easily grasped way and said : "consider the color-negative having lines of red, green and blue, and imagine this to have been exposed to green light, and developed, so that the green stripe is black ; now print it on a similar film put over it at right angles, and consider the nine squares thus formed, first with regard to the negative, and then to the positive produced upon
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development, Fig. 135. Square 1 is formed by the crossing of red through red, and will be transparent in the negative, forming a black in the positive. Square 2 is red through green, is black in the negative, and transparent in the positive. Square 3 is red on blue, black in the negative, transparent in the positive. Squares 4, 5, and 6 have the silver deposit on them, and give transparent squares in the positive. Square 7 is blue on red, black in the negative, and transparent in the positive. Square 8 is blue on green, black in the negative, and transparent in the positive. Square 9 is blue on blue, is transparent in the negative, and black in the positive. So that of our nine squares in the positive, seven are transparent, and instead of having only green, we have, to three greens, two reds and two blues ; thus producing always faint colors degraded with greys. This result is easily confirmed by direct experiment, and however the squares be arranged, whether in lines or patterns of any particular shape, it must always happen that to three greens there will be two reds and two blues ; or to one square of pure color there will be six squares making two whites.
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