Frequently the varnishing of the placards is done with gelatin. This imparts to the picture an especially handsome, luminous luster. After an equal quantity of alcohol has been added to a readily flowing solution of gelatin, kept for use in a zinc vessel, the gelatin solution is poured on the glass plates destined for the transparencies. After a quarter of an hour, take the placard, moisten its back uniformly, and lay it upon a gelatin film which has meanwhile formed on the glass plate, where it remains 2 to 3 days. When it is to be removed from the plate, the edge of the gelatin film protruding over the edge of the placard is lifted up with a dull knife, and it is thus drawn off. A fine, transparent gloss remains on the placard proper. In order to render the covering waterproof and pliable, it is given a coating of collodion, which does not detract from the transparence. The glass plates and their frames must be cleaned of adhering gelatin particles before renewed use.
TRANSFER PROCESSES:
To Transfer Designs.
To Copy Engravings.
To Transfer Engravings.
TRICKS WITH FIRE: See Pyrotechnics.
TUBERS, THEIR PRESERVATION: See Roots.
TUBS: TO RENDER SHRUNKEN TUBS WATER-TIGHT: See Casks.
TUNGSTEN STEEL: See Steel.
TURMERIC IN FOOD: See Foods.