mask all the map except the portion that is to be colored. Heavy wrapping 

 paper is used for this purpose. For lithofacies maps, slotted stencils can be cut 

 from stiff paper or cardboard. The stencil is laid over the exposed part of the 

 map; and the air brush, set on a wide spray, colors the map in bands. When the 

 first color is dry, the stencil is offset one space and the second alternating color 

 is applied. If three color bands are required, two stencils are needed. They are 

 placed one on top of the other and are shifted until the desired exposure of the 

 map surface is attained. 



Printers' Ink 



Colored printers' inks provide a means of coloring large areas with a uni- 

 form tone, with no evidences of overlap. Since the inks have a grease base, there 

 is no scale change in the map. The method is easy and fast, and the results are 

 nearly as flawless as printing. This method was developed by Geophoto, Inc., 

 Denver, Colorado. 



The viscous printers' ink is thinned with about three parts of mineral 

 spirits to one part of ink. Thorough mixing is essential. 



The color is applied with a sable artists' round brush of size 6 to 12, de- 

 pending on the size of the area to be colored. All of the surface must be covered, 

 but need not be spread evenly. When an area of 5 or 6 inches square has been 

 covered, a double thickness of facial cleansing tissue is laid flat on the moist color 

 and patted down so that the excess ink is absorbed. A pad or wad of the tissue 

 is used to wipe and rub all free color from the map. When the color is extended, 

 the edge previously colored is overlapped. There will be no visible overlap when 

 this is wiped with the cleansing tissue. 



Better results can be expected if the border areas are colored first with a 

 medium-sized brush not too heavily charged with ink. A larger brush may be 

 used in the central parts. The darkest colors are applied first. If this procedure 

 is followed, no overlaps will show, even where two different colors are involved. 



There is no satisfactory means of removing the printers' ink from the 

 paper. Therefore, considerable care must be taken that the color is applied 

 correctly. Maps colored by this method may be soaked in water for cloth 

 mounting without danger of disturbing the colors. Colored areas will take color- 

 ed pencils within a few minutes, but they should be given several hours or days 

 to dry before ink lines are attempted. 



The printers' inks can be mixed to obtain an infinite variety of shades. 

 Pastel tints are obtained by mixing the colors with the white transparent base. 

 Colors must be mixed before they are applied to the map because, as suggested 

 earlier, the paper becomes charged with the first color applied and is, thereafter, 

 resistant to further applications. Within reasonable limits, the viscosity of the 

 color has no effect on the hue or tone on the map: i.e., the same color is obtained 

 with either a thin or thick mixture. 



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