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THE POPULAR SCIENCE MONTHLY. 



specially prepared ink. The parts not coated are thus the only 

 ones exposed when the piece is phinged into the bath of hydro- 

 fluoric acid. They are soon bitten by the acid, and in this way the 

 design is traced upon the glass. As globes for lamps and gas are 

 the subjects most frequently chosen for this treatment, the process 

 can, perhaps, best be understood by following such an article 

 through the several stages of its decorative development. The 

 designs are adapted from a variety of sources. The draughtsman 

 is supplied with drawing-books containing examples of conven- 

 tionalized flowers. From this unit he works out a design of 

 proper size and shape — that is, something which when wrapped 

 around the globe shall cover just one half of it, and so, by repeti- 

 tion, the whole. He traces his designs on a panel of heavy plate 



Pig. 8. — Four Stages : To the right, the plain ground globe ; then the globe wrapped in printed 

 paper; next, the printed globe, with the paper removed; and finally, to the left, the finished 

 product. 



glass. The surface is coated with a special ink made of lamp- 

 black, rosin, and wax, and the design then picked out by means of 

 a sharp tool. The plate, thus prepared, is subjected to the action 

 of a strongly acid bath of hydrofluoric acid for a period of from 

 fifteen to twenty minutes. The uncovered parts of the plate are 

 deeply eaten away. The ink is then washed off, and the plate is 

 ready to print from. Frequently designs are etched on both sides 

 of the panel, both for economy of material and of storage. 



The printing is done on a simple engraver's press, the im- 

 pressions being taken upon smooth, white paper, somewhat heavier 

 than tissue. As the ink used for the purpose has a decided tend- 



