Scientific American Supplement, No. 362, December 9, 1882 by Various
page 59 of 140 (42%)
page 59 of 140 (42%)
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that the yellowish tinge is by no means inseparable from good results.
The washed and dried plate should appear like a design of ground and polished glass. The ground glass appearance is given by the grain. If there are pure high-lights (almost transparent) and opalescent shadows, the plate is a good one. _Printing from the Block_.--We have now a printing-block ready for the press. If it is to be printed by machinery--that is to say, upon a Schnell press--the surface is etched; if it has to be more carefully handled in a hand press, etching is rarely resorted to; it is moistened only with glycerine and water. To etch a plate for a Schnell press, it is placed upon a leveling stand, and the following solution is poured upon it: Glycerine............................. 150 parts. Ammonia................................ 50 " Nitrate of potash (saltpeter).......... 5 " Water.................................. 25 " Another equally good formula, recommended by Allgeyer, who managed Herr Albert's Lichtdruck printing for some years, is: Glycerine............................. 500 parts. Water................................. 500 " Chloride of sodium (common salt)...... 15 " In lieu of common salt, 15 parts of hyposulphite of soda, or other hygroscopic salt, such as chloride of calcium, may be employed. |
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