While the glass is still wet from the washing, after being taken
from the acid, it should be coated with a preparation of albumen,
prepared as follows: [p012]
To the albumen or white of a fresh egg, add eight ounces of water;
put it in a bowl and thoroughly beat it with an egg beater, or in
any manner that may be convenient, until the fibre or structure is
completely destroyed, when it should be filtered through loose
cotton, and after the addition of a few drops of strong ammonia, it
is ready for use.
Many prefer to beat up the albumen before adding the water, in which
case it should be beaten into a stiff froth, when the proper amount
of water is added, and after the froth has subsided the whole is
filtered and the ammonia put in last.
The albumen being prepared and the glass ready, a square is taken in
the left hand, and clean water flowed over it, until no particle of
dust can be seen adhering to either surface, when a small portion of
the albumen is flowed on it, and after covering every part of the
surface the excess is allowed to drain off the right hand lower
corner, after which, if running water is at hand, the back of the
same portion of the plate should be passed under the faucet, and the
water will carry off any excess of albumen which might return or
crawl, as it is termed, up the back of the plate from the point
where it is drained.
The greatest care should be taken to avoid dust settling on the
plate during the coating and afterwards while drying, and after the
glass has been coated, if it is found that any dust adheres to the
albumenized surface, it should be again washed and recoated.
It is important that the back of the glass should be kept free from
the albumen, so that when the plate is afterward collodionized and
immersed in the silver solution, there should be no albumen
uncovered to [p013] contaminate the bath, and as most of the
glass used has some slight inequalities of surface, the albumen
should always be flowed on the concave side, for two reasons:
The first is, that when sensitized and placed in the holder, the
pressure, being against the convex side, may have a tendency to
counteract the curve and make the plate flatter and more perfectly
adjusted to the focus.
The other reason is that the pressure of the printing frame has a
less tendency to break the glass when against the concave side.
The amount of glass required having been albumenized and set up in
racks, it should be carefully covered with paper to exclude dust,
and it should be set away to dry, after which it should be placed in
its proper receptacle in the dark room, ready for use.
The reasons for albumenizing the glass are important.
Before this process was adopted, all glass used for photographic
purposes, after being subjected to the action of potash or acid, or
both, had to be finely polished with rottenstone or some other
polishing substance, to render its surface sufficiently free from
all traces of acid, organic matter, rust, etc., which would
injuriously affect the collodion or the deposit of silver iodide
derived from the bath.
This polishing was very laborious, and in consequence it was often
very imperfectly done, causing much loss of time and material; also
the glass thus prepared did not offer to the collodion a surface to
which it could adhere with much tenacity, and in consequence it
would frequently slip from it in the subsequent manipulations. [p014]
The first reason for Albumenizing then, is to cover the surface with
a substance chemically pure, and when dry of a crystaline nature and
impervious to, or at least not soluble in the silver solution, thus
saving the labor of polishing.
Another reason is that the albumen offers a surface to which the
collodion will adhere with extreme tenacity, thus saving and
preventing the film from slipping.