Page 39 - The Wellington photographic handbook

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To prevent this defect, plates may be obtained with the glass
side covered with a coating capable of absorbing the light that
passes through the film and preventing its reflection. A plate so
prepared is called a " backed " plate.
WELLINGTON plates are backed with a red transparent
medium which is practically invisible in the dark-room and allows
the progress of development to be watched by transmitted light
just as readily as if the plates were unbacked.
This backing should not be sponged off, as is necessary with
ordinary opaque backing. The plate should be treated in the
usual way, and it will be found that the operations of development
and fixation will cause the backing entirely to disappear. The
dissolution of the backing causes the developer to assume a deep
red colour, but its activity is in no way diminished, and the red
stain has the effect of protecting the plate from any fogging action
of the dark-room light.
It should here be mentioned that the extent to which an
unbacked plate is liable to halation is largely determined by the
nature and richness of its coating. WELLINGTON plates are
famous for their thick, rich coating, and their consequent freedom
from halation. The reader will therefore find that for most ordinary
purposes he can safely use his plates unbacked, but when photo-
graphing interiors, backed plates should always be used.
The WELLINGTON Silver Intensifier.
Negatives which are not sufficiently vigorous owing to some
error in manipulation, such as over-exposure or under-development,
may be greatly improved by the process of intensification.
The film should first be hardened in the following bath :
Formaline 1 part
Water 10 parts
In this bath the negative should be allowed to remain for five
minutes, after which it should be rinsed for a few minutes and then
placed for exactly one minute in the following bath :
Potassium Ferricyanide ... 20 grains 2-3 grammes
Potassium Bromide ... ... 20 2-3 ,,
Water to 20 ounces 1 litre
This bath, which should never be omitted, has the effect of
preventing stains during the process of intensification.
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