Identifier: horganshalftonep00horg (find matches)
Title: Horgan's half-tone and photomechanical processes ..
Year: 1913 (1910s)
Authors: Horgan, Stephen Henry, 1854-1941
Subjects: Photomechanical processes
Publisher: Chicago: Inland Printer Co
Contributing Library: Getty Research Institute
Digitizing Sponsor: Getty Research Institute

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mage on the paper at the same time thewater penetrates through the unhardened gelatin coating andrepels the ink from its surface. This can be determined whenthe inked print begins to lose its original gloss. The printis then removed to the wet surface of a sheet of plate glass,laid on it, and with a wet soft Turkish sponge the ink iswashed away from the gelatin surface where the light hasnot acted upon it, leaving an image in sharp lines of transferink. The print is plunged into clean water and left until allof the soluble bichromate of potash is dissolved out of it,when it is hung up to dry. While drying, all water spotsthat rest on the image must be removed with the edge ofpieces of blotter because they contain a slight trace of gelatinwhich, drying on the lines, would prevent them transferring.When the transfers are dry they are ready to be transferredto lithographic stone, aluminum, or zinc plates, either fordirect printing from zinc or from zinc on the offset pressafter reversal.
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A COLLOTYPE COLLOTYPE. METHOD OF PRINTING FROM GELATIN IN THE LITHOGRAPHICMANNER. Collotype is one of the earliest of the photomechanicalprinting processes. In Germany, where it is worked mostsuccessfully, it is called lichtdruck, in France, phototypie,and in the United States it is known as albertype, artotype,heliotype, autogravure and plain gelatin printing. Itsproper title is collotype, and it has come down to us fromLouis Alphonse Poitevin, a French chemist and engineer,who received a prize for the process in 1855. It wasimproved upon since that time by Tessier du Mothay, Lemer-cier, Albert, Obernetter, Husnik, Sprague, Sawyer, ColonelWaterhouse, Ernest Edwards, T. C. Roche, and others.So the method has proved worthy of the attention of thebrightest experimenters in photomechanical printing. The results possible of attainment by collotype aredeserving of study by processworkers and particularly thosewith a knowledge of lithography. THE PRINCIPLE OF COLLOTYPE. Collotype is a proce

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