PAPER NEGATIVES Fox Talbot, in his calotype process, worked extensively between 184r and r856, made his negatives from paper coated with a sensitive silver salt, but this system became almost obso lete when Archer introduced his collodion process on glass. About 1885, however, paper as a medium for negatives again came to the front owing to the increasing popularity of bromide paper, which originally was intended solely for printing by development. In 1884 a specially rapid bromide paper was introduced for negative work, and the Eastman Company and other firms followed with improvements. At the present time celluloid films, roll or flat, have almost superseded paper as a support for the emulsion, but there are still a few photographers who use bromide paper for negative making. Compared with glass, paper is lighter, halation is impossible, it is not brittle, it can easily be stored, it is cheap, and it can be easily cut ; but it is not transparent, and, consequently, the time taken in printing is rather long ; the grain may be troublesome, and print at the same time as the image, although, if the printing is done on a matt or rough paper, it will be considerably minimised, and possibly caused wholly to disappear. Paper cannot be obtained with so high a rapidity as the fastest plates, and there is a slight difficulty in keeping it flat in the dark-slide and in developing and fixing it.
Generally, bromide paper can be used in exactly the same way as a dry plate, the thinnest, with a semi-matt surface, being the most suitable. Up to half-plate it may be kept flat in the dark slide without difficulty, but beyond that size some little care is necessary, while it will be advisable to place a sheet of glass or cardboard at the back of the paper, and it may be necessary to coat the extreme edge of the glass or card backing (or the division plate, if a backing is not used) with a mixture of gelatine and glycerine or similar adhesive. The exposure with an
average paper is about three times as long as with an average dry plate ; but it depends on the circumstances. Under-exposure must be particularly guarded against. The developers advocated by the paper-makers should be used, and not those specially for plate work ; those most suitable are the clean-working developers, such as metol, hydroquinone, amidol, rodinal, etc. Pyro is unsuitable, as it tends to give the shadow (white paper) parts a yellowish tinge, thus prolonging the period of printing. When developing, remember to judge the density by looking through the paper and not upon it. The developed negative is fixed in an acid fixing bath in order to avoid stains, and make the negative as dear as possible. The paper negative is washed, dried, reduced, intensified, toned, etc., in the usual way. Printing is facilitated by waxing the paper to render it more translucent, but most makes of thin smooth bromide paper do not need this treatment.
Four methods are here given for increasing the translucency of paper negatives :— (1) Rub on warm vaseline with a dean rag to the back of the negative, and apply a warm flat-iron, interposing a sheet of blotting-paper. Should any vaseline get on the film side, remove with benzine. (2) Use white wax and a warm iron as above. Any superfluous wax may be partly removed with turpentine. (3) Apply, as above, a mixture of alcohol 4 oz., and castor oil oz. Ironing is not necessary in this or in the next method. (4) Apply, as above, a mixture of turpentine 5 oz., and Canada balsam i oz.