The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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Sympathetic Photographs
Textiles, Printing on
Sympathetic Photographs. An image composed of in-soluble gelatine is formed in the mass of a sheet of unsized paper, so that when the sheet is dipped in water the image appears, by reason of those portions free from gelatine becoming transparent. As the sheet drys the image disappears. If, on the other hand, the sheet is saturated with varnish, the image remains. Soft, unsized paper is soaked in a warm bichromated gelatine solution (5 of gelatine, 100 of water, 1 of bichromate potassium), and when dry is exposed under a negative. All soluble matter is now removed by soaking in warm water. Prints of this kind were made and exhibited by Mr. Stone many years ago. Such a print may be employed as a kind of stencil, if a dye solution is allowed to ooze through it.
Synthol Developer. See Development and Developers.
Talbotype. See Calotype.
Tannic Acid (Ger., Gerbsdure; Fr., Tannin). C^H ^0,7=618. This is not a true acid, but a glucoside obtained from galls. Solubility: 10 in 8 of water, 10 in 8 of alcohol, sparingly soluble in ether, its photographic use being limited almost, if not entirely to the old collodion process.
Tartaric Acid Ger., Weinsteinsaure; FrM Acide Tarlarique)^ H2C4H406 = 150. Prepared from the impure cream of tartar in the lees of wine by precipitation by chalk, and subsequent addition of sulphuric acid. Solubility: 1 in *66 of cold water, 1 in .5 of boiling water; soluble also in alcohol and ether. Its use in photography is limited, being sometimes used instead of citric acid, and for preserving sensitised paper.
Tea Process. Infusion of tea used as a preservative or organifier of the wet collodion film.
Telephotographic Lens. See Lens.
Telephotoscopy. See Electric Telephotoscopy.
Testing, Chemical. See Analysis.
Test Papers. Small slips of bibulous paper soaked in a solu-tion of litmus or other dye, and used for testing any liquid for its alkalinity or acidity.
Textiles, Printing on. See Silk, Diazotype, and Dyeing. For enlarging on canvas, see Enlarging.
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