Horgan's half-tone and photomechanical processes .. . race of grease, which must be removed or it will appear asminute round bare spots where the gelatin does not cover the PHOTOLITHOGRAPHY 15 paper. To get rid of any possibility of grease in the coatingthe 160 grams of gelatin must first be put to soak in theone thousand grams of water until it has absorbed all of thewater, then the albumen of two eggs is stirred into the gela-tin. The soaking of the gelatin had better be done in one ofthose stoneware breakfast-food cookers consisting of twovessels fitting one inside the other. The lower vess
Horgan's half-tone and photomechanical processes .. . race of grease, which must be removed or it will appear asminute round bare spots where the gelatin does not cover the PHOTOLITHOGRAPHY 15 paper. To get rid of any possibility of grease in the coatingthe 160 grams of gelatin must first be put to soak in theone thousand grams of water until it has absorbed all of thewater, then the albumen of two eggs is stirred into the gela-tin. The soaking of the gelatin had better be done in one ofthose stoneware breakfast-food cookers consisting of twovessels fitting one inside the other. The lower vessel con-tains water which boils over heat, while in the upper vesselis placed the gelatin to dissolve while the albumen is wellstirred in. The upper vessel is then covered and the gelatinand albumen allowed to cook for half an hour, or untilthe albumen appears to be coagulated and is floating withother foreign matter on the surface of the heated the gelatin while hot through a muslin bag into aglazed pitcher or an enameled-ware SIMPLE APPARATUS FOR COATING PAPER. Gelatin is exceedingly sensitive to chrome alum. Theslightest trace of the alum has a hardening effect on it, to adegree, so that it is necessary to add the alum to the bichro-mate of potash and grind both in a mortar to a fine powder,and then while stirring the hot gelatin pour in the bichromatepowder slowly. The acetic acid can then be added and thewhole filtered again. The first method I employed for coating the paperrequired two pairs of hands. One pair of hands to pull thepaper through the guard and the other pair to lower the 16 horgans half-tone guard to just the right depth on the surface of the tin trough to hold the gelatin and the construction ofthe guard are shown in the diagram. The guard is made of well-seasoned hardwood, witha piece of No. 8 brass wire secured to it with two screws atboth sides. The wire guides the sheet of paper to the edgeof the scraper so that the pa
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Keywords: ., bookcentury1900, bookdecade1910, bookidhorganshalft, bookyear1913
