Camera Work: A Photographic Quarterly (1905 (Heft 11))

to mix with the sensitizing solution when coating; just five drops should be
added to the two drams of sensitizing solution and stirred round with a
glass rod. Fish glue has a tendency to coagulate into clots with the more
recent sensitizing solutions.
Exposure.—If we were fortunate enough to always expose correctly
nearly all our difficulties would vanish. To make an accurate exposure,
either in the camera or in the printing-frame, is one of the most difficult
things in photography. It requires practice even with photometers, but
where one can see the image growing under the influence of light, the
operation becomes much easier. In ozotype and aristo the amount of the
light-product is visible and the coloration is a measure of the light passing
through the negative. The usual carbon actinometers do not measure the
light that is passing through the negative, and a trial or two is necessary to
determine the ratio of the light which the negative allows to pass and the
chemical activity of the light before it enters the negative. A visible image
must therefore be a far better guide to exposure than an actinometer.
Ozotype follows the law of most other printing processes. Strong
negatives are better exposed to sunlight and weak negatives in the shade.
Print until the details in the half-tones are visible or until the details in the
high lights can only just be seen. A good plan is always to keep your eye
on the margin that has been covered by the rebate of the printing-frame.
You know that this has not received an exposure, and a comparison between
this unexposed strip and the printed portion is a great assistance in judging
the extent of exposure. Light clouds will probably not show on the initial
image, but they will appear in the finished picture if kept long enough in
contact with the plaster. When a weak negative is being printed from, a
weak image will, of course, result. In this case do not overexpose or print
through the high lights. Everything will come right afterward by leaving
the print in contact with the plaster a longer time, say forty-five minutes to
one hour.
The sensitive salt that will give the deepest colored image does not
possess the highest pigmenting quality. The color of the initial image
depends to a large extent upon the sizing and quality of the paper used.
A paper strongly sized with gelatine, such as the F paper, will not give an
image so strongly colored as a thinly sized drawing-paper, but the keeping
quality of the sensitive F paper will be six or seven times better than the
drawing-paper. The rule to be observed is, when you are using an unknown
paper, or, in fact, all papers not specially manufactured for photographic
purposes, keep the sensitive surface upon it as short a time as possible, make
your print, and then wash away all the sensitive material.
Washing. — Some readers might think that washing the print is an
extra “fag” which is not required in carbon-printing. In carbon-printing,
the same as in ozotype, the sensitive salts must be thoroughly removed or
the print will suffer. In carbon-printing the sensitive salt is partly washed
away in the hot developing-water, but it is absolutely necessary that any
remaining bichromate should be removed, and therefore a final alum bath