Another method* is with— Gelatine 45 grains White soap 45 grains Water 5+ fluid ounces Soak the gelatine in the water for five or six hours, then dissolve it with the aid of a water bath, Cut the soap into small pieces, and add to the gelatine solution, stirring the whole with a glass rod to insure a perfect mixture; then add powdered alum until the froth disappears, and strain through muslin. Cover the block with this mixture and a little zinc white, then wipe off so that a very thin film will be left, rubbing it gently so that the film may be of as even a thickness as possible. After drying apply with a wide badger-hair brush a coating of the following: Albumen 31 fluid ounces Water 2; fluid ounces Sal. ammonia 67; grains Citric acid io grains Whip the albumen to a froth and allow it to settle; to the limpid portion add the water, then the sal. ammonia, stir, and then add the citric acid. When the block is dry, sensitize with a solution of— Water 31 fluid ounces Nitrate of silver 187 grains Pour this upon the surface of the block, spread it evenly with a glass rod, and pour off the excess. When the block is dry expose under a negative in the usual manner until it is printed the exact shade required. When printed immerse the printed surface in a very strong solution of salt for about three minutes; then wash in a stream of water for a short time, and fix it by placing it face downwards in a saturated solution of hypo. After fixing wash under a stream of water for about ten minutes; when dry it is finished and ready for the engraver.
The American process, said to be the one adopted by the splendidly-illustrated monthly magazines published in this country, is said to be as followst: First make a reversed collodion transparency in the camera from the negative. A tough and horny collodion should be used. Develop with Pyrogallic acid too grains Citric acid 6o grains Acetic acid 2 ounces Water zo ounces and fix in hyposulphite of soda. Coat the with the following hot solution of gelatine : Gelatine 4 ounces Water t pint Dissolve the gelatine by placing in a vessel of warm water, and then add 4 grains of chrome alum and mix thoroughly. The wood, having been coated, is allowed to dry. The gelatine surface is then moistened with water for ten or fifteen minutes, and the transparency, still wet from the washing water, is laid down upon it and pressed lightly in contact, and allowed to dry under slight pressure. When dry, the collodion readily leaves the glass, and remains in contact with the block Here are some further points :—The plate is cleaned as usual, and dusted with powdered talc and polished off ; it is then coated with positive collodion, sensitized and exposed as usual, fixed with cyanide of potassium, and placed in a dish of warm water. In the meantime, have
your block blackened by rubbing drop black on it, or ordinary blacking, and coat and drain well with a solution of the commonest glue you can get, one ounce to twelve ounces of hot water ; the common glues are the best, for they take a much longer time to set than better ones, and so you can get a much thinner coat with draining. Place your block in a vessel of water, having it im mersed about three inches, then bring your photo from the dish, place it over the block and under the water. You will find by touching the edges of the film it will readily leave the glass ; you can then turn it about any way under the water, and when in position, raise your block gently out of the water, bringing the film with it ; if it is puckered at all, it is owing to raising too roughly, and must be placed in the water again. If satisfactory, place at an angle to drain, and dry in warm, airy place. The whole operation, from focusing to getting the block ready for drying, will not take a practised hand more than twenty minutes. The common glue will not block the tool at all if you drain the block well, and when cut all can be removed immediately with a sponge and warm water. A very good way to black the block is to hold it over a petroleum lamp with its chimney removed. The glue-water will not come off it if applied in the same man ner as applying varnish to a negative, and under no circumstances be induced to use a black varnish, for it is next to impossible to do a good job, for the graver slips as if it were cutting on glass.
Harris's process does not strictly come under this heading, as an indiarubber block is used instead of wood, but it may be given here, as it is also a process intended as a help to the engraver. Hard rubber is first procured in smooth black polished sheets, about A in. thick. These are cut and trimmed to the size required, cleaned, and albumenized in the same manner as glass for negatives.
The rubber plate is next coated with collodion, sensitized in the silver bath, exposed in the camera, and developed in the usual way of making a negative. The whole operation is very similar to the ferrotype process, except that the image is made upon rubber instead of iron.
When a clean sharp image is obtained it is fixed in cyanide and varnished with a very thin transparent varnish and dried by a gentle heat. The plate is now ready for the engraver.
WOOD SPIRIT.—See Methylic Alcohol.