Items related to Practical guide to photographic & photo-mechanical...
Synopsis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1887 Excerpt: ...a surface prepared with wax or somo such substance. To this surface it will adhere whilst it is wot, but not when it is dry j us u consequence, if tho print bo developed on this surface, as described in tho last chapter--if, afterwards, whilst it is still wot, there bo applied to it a support, of paper or other material, to which it will adhere when dry, and if tho wholo bo then allowed to dry, tho print will loavo tho support on which it was developed, and will rc:r.:'.in on tho second ono, in which case it will no longer bo reversed. Tho surface on which tho print is first developed is known M a temporary support. Temporary supports aro of two kinds--rigid and flexible,:, Rigid Support The form of rigid support which has found most favour is one of zinc, thick enough to bo manageable and finely ground or mulled on one eido. An,hour or two before development in to take place each sheet of zino is waxed by carefully rubbing over it with a pioco of soft flannel a mixture composed us follows:--BcoVwiix 3 drams Yellow resin.... 0 „ Oil of turpentine... 1 pint It is also necessary to got ready the final support on to which the print is to bo transferred aftor development, fixing, etc., are complete. Until quite lately the final support almost always consisted of paper or other material coated on one side with gelatine rendered semi-insoluble by the action of chrome alum. To use it, the support was soaked in water of such a temperature as would render the gelatine slimy. The only objection to this arrangement was that the gelatine tended, by keeping, to become more and more insoluble, so that it was always a question of experiment to discover what temperature of water was necessary to bring the surface into the required condition. Recently the Autotype Com...
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