We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
THE OPTICAL LANTERN AND CINEMATOGRAPH JOURNAL.
(05
ON THE DEVELOPMENT OF LANTERN PLATES.
By Rev. T. Perkins.
ALMOST any 1 educing agent that can be used for the development of negative plates — pyrogallic acid, hydroquinone, metol, eikinogen — will serve for the development of lantern slides. My own favourite of these is hydroquinone, as it is easy to work, and by its means, without any subsequent toning, a great variety of colours — black, brown, purple or red, can be produced. There are three main ingredients in the solutions: (1) hydroquinone, with a preservative, either sodium sulphite or potassium metabisulphite ; (2) caustic soda or caustic potash ; (3) potassium bromide.
It is a safe rule if we use but one brand of plates, to adopt the hydroquine formula given by the makers of that particular kind of plate. The formula? of different makers are given in such different ways that comparison becomes rather troublesome, one maker for instance may direct that equal quantities of his stock solutions are to be mixed, and the developer is then ready for use ; another, that the stock solutions when mixed are to be diluted with water. It is a pity that all formula; are not given in the same way, by merely stating how many grains of each constituent are to be present in an ounce of developer ready for use. I have analysed some of the leading makers' formula?, and find that the number of grains of hydroquinone present in an ounce of developer varies from 2 to 4. Much greater variation is found in the amount of the other two components. These two are : an accelerating agent — the caustic scda or potash; and a restrainer — the potassium
bromide ; so that if more of one is used, then more of the other is required to keep it in check.
The formula I use myself is : — A.
Hydroquinone Potassium Metabisulphite Potassium Bromide ... Water
Joz. |-oz.
40-grs.
io-oz.
B. Caustic Soda
Water
C. (for modifying tones.)
Ammonium Carbonate Ammonium Bromide Water
i-oz.
IO-OZ.
i-oz. |-oz.
IO-OZ.
For use, take j-oz. of A, i-oz. of B, and h-oz. of water. It will be seen that if io-oz. of A, io-oz. of B, and 20-oz. of water are mixed, the proportion will be the same. That is, in 40-oz. of solution there would be ± of an ounce (iogf grs.) of hydroquinone and of caustic soda, which works out to 273, or about 2f grains per ounce, and of potassium bromide 1 grain.
This developer gives a warm black tone on most plates if the exposure has been correct ; by increasing the exposure and adding to the ounce of developer some of the C solution, the colour can be warmed.
Thus if 1 minute were required for a black tone,
2 minutes and 30 minims of C would
give a brown tone ;
5 minutes and 60 minims of C would
give a purple tone ;