210 The Ohio Journal of Science [Vol. XVII, No. 6, 



other hand, which involve great technical skill in the worker 

 are expensive. 



Etching on metal, lithography and wood cutting since they 

 involve skilled technicians are costly reproductions as compared 

 to the half tone method and the method of zinc engraving which 

 utilize photography directly. 



For all methods involving photography it is best to have 

 black ink drawings on a white ground. Good pencil drawings 

 can be used, but the ink gives the greater contrast. 



In making drawings it is often necessary to transfer to a 

 clean sheet of Bristol board or water color paper. Paste tracing 

 paper with unboiled flour paste (which will not spot paper) on 

 your drawing. Trace over the outlines lightly, then loosen the 

 tracing paper, reverse it on a window pane or on the glass 

 top of a box containing an electric light, go over the outlines 

 with heavy, soft pencil, and by careful pressure you have the 

 outline transferred to the fresh Bristol board. The use of car- 

 bon paper for transferring is somewhat dangerous as other 

 blotches may be transferred to the clean sheet beside the lines 

 which you wish. For erasing use sponge rubber or Fabers 

 kneaded rubber so that you will not injure the surface for 

 water colors. 



To lay a flat tint use a brown or red sable brush — common 

 camel's hair is not good. The brush should jar to a perfect 

 point, it should be large so as to hold much liquid. It must be 

 elastic so as to spring to position instantly. You must not lay 

 it down flat, always keep brushes in a glass, point up, to preserve 

 the point. 



The water color paper or Bristol board must be wet all over 

 first to keep from spotting it with your wash or colors. A 

 camel's hair brush can be used to take up excess of color when 

 laying a tint. If you have too much color, add water and take 

 up with nearly dry camel's hair brush. The evenest washes 

 are those made with Prussian blue, carmine, olive green, indigo, 

 neutral tint, vandyke brown, most of the yellows. Those which 

 dry too quick and so are likely to make spotty work, cobalt, 

 Vermillion, ultramarine, most of the greens, most of the blacks, 

 burnt sienna and sepia unless very thin. When one wants very 

 rich reds or browns as in drawing of kidney, it is not obtainable 



