Coating with Albumen.
Having allowed the plate to drain one minute, place it again on a levelling stand, with the film upwards, and pour over it as much of the iodized albumen as the plate will hold, from a glass measure containing not more than enough of the albumen to coat two plates with, pour off the excess into the measure, and again cover the plate with albumen three separate times; ultimately drain off as much as possible of the excess of albumen, and place the plate nearly upright against the wall, with the coated side inwards, to dry, which takes place in an ordinary temperature in about one hour.
In coating with albumen, the presence of air-bubbles or dust must be guarded against. The former can be easily done by taking care, in pouring the albumen into the measure and on the plate, not to pour so as to generate air-bubbles in the liquid. But should any be detected, hold the plate horizontally and give it another coating of albumen, then incline the plate so that the bulk of the liquid shall pass over and carry off the bubbles with the running stream. Dust on the plate must be prevented by operating in a room as free from this photographic enemy as possible.
In order to render the coating of albumen as uniform as possible, the plate must stand to dry on two or three layers of filtering paper and the upper surface must touch the wall at one point only and not to be allowed to rest against it along its entire upper edge.
When the albumen coating is thoroughly dry (and not till then), the plate is ready to be excited, but if more have been prepared than are likely to be used for taking pictures on during the next ten days or fortnight, they may be stowed away in a plate box, ready to receive the sensitive coating at any time. The author's experience has led him to believe that these albumenized plates will keep good any length of time, as plates which had been coated a month, when excited, exposed, and developed, appeared to possess all the properties of recently prepared plates.
Exciting the Albumen Coating.
Prior to the plates being excited they must be thoroughly dry and free from any particles of loose dust on the surface, back, or edge. Sufficient of the albumen bath solution, [page 192], must be filtered through filtering paper to fill a dipping bath of the required size, so that the plate can be immersed in it.
The careful filtering of the fluid is very necessary in order to free it from any floating particles, and to separate the animal charcoal.
The plate is now taken and laid, albumen side upwards, on the dipper, and then lowered into the bath with one steady downward movement, where it is allowed to remain one minute; it is then taken out, the excess of liquid drained off, and placed on the fixing stand, with the albumen surface uppermost, and a stream of water poured over it for at least one minute, so as to remove every particle of the bath solution. This complete washing is very necessary, in order to prevent stains in the after development, which invariably takes place around the edges, if not thoroughly washed. The plate having been thoroughly washed, is leaned against a wall to dry, or if required for immediate exposure, may be dried on a plate of heated metal or foot warmer, but in no case must the exposure in the camera take place until the surface is thoroughly dry.