The material employed is very troublesome to prepare, and on this account, as well as because of the risk of failure attending the use of home-made articles, it is far preferable it should be purchased. It may be obtained under the name of ‘Kennett’s Sensitised Pellicle.’
This pellicle consists of shreds of dry gelatin containing the sensitive salts.
Fresh directions accompany each packet of the “Sensitised Pellicle.”
The Honey Process. Let the plate be cleaned, coated, and sensitised in the usual manner; then place it in a bath of distilled water, washing it more or less, as it may be required to be kept for a longer or shorter time. Pour on the plate a solution made of equal parts of honey and distilled water in the same manner as when using collodion; throw away the first portion, and repeat the operation, letting the solution soak in for one or two minutes; pour back the honey solution into its bottle; drain the plate on blotting paper, and keep it in the dark free from dust. The time required for exposure of the plate is about double as long as in the ordinary wet process.
The plate should be soaked in distilled water previous to being developed, in order to soften or remove the film of honey; the older the plate the longer it will require to be soaked, afterwards dip the plate in the silver bath, and develop in the usual manner.
The Carbon Process. In this process, the adoption of which is daily increasing, the material employed consists of a layer of gelatin containing carbon, or some other permanent pigment, spread on paper.
In this condition the paper is not sensitive to light, but if it be treated with a solution of bichromate of potash, dried in the dark, and afterwards exposed to sunlight under a negative, those portions of the paper which have been acted upon by the light will become insoluble, whilst those parts that have been protected from it will be soluble. When, therefore, after sufficient exposure, the prepared paper is removed from the negative, a picture the reverse of the negative will have been formed, in which the pigmented gelatin alone remains, and performs the part of the reduced silver in the ordinary photograph.
If the film, after exposure to light under a negative, is soaked in warm water, all the parts which have been protected from the action of the light can be dissolved, and a relief is formed which, when dry, is sufficiently hard to transmit its shape to lead. From
the mould or plate thus obtained a comparatively large number of impressions can be taken, either with coloured gelatin or with fatty colours, the well-known Woodbury-type being the most successful of the several processes based on the fact.
Photographic Varnish. See Varnishes.