When the ingredients are mixed, take a bundle of quills or a fork, and beat the whole into a perfect froth. As the froth forms, it is to be skimmed off and placed in a flat dish to subside. The success of the operation depends entirely upon the manner in which this part of the process is conducted; if the albumen is not thoroughly beaten, flakes of animal membrane will be left in the liquid, and will cause streaks upon the paper. When the froth has partially subsided, transfer it to a tall and narrow jar, and allow to stand for several hours, that the membranous shreds may settle to the bottom. Pour off the upper clear portion, which is fit for use. Albumenous liquids are too glutinous to run well through a paper filter, and are better cleared by subsidence.
A more simple plan than the above, and one equally efficacious, is to fill a bottle to about three parts with the salted mixture of albumen and water, and to shake it well for ten minutes or a quarter of an hour, until it loses its glutinosity and can be poured out smoothly from the neck of the bottle. It is then to be transferred to an open jar, and allowed to settle as before.
The solution, prepared by the above directions, will contain exactly ten grains of salt to the ounce, dissolved in an equal bulk of albumen and water. Some operators employ the albumen alone without an addition of water, but the paper in that case has a very highly varnished appearance, which is thought by most to be objectionable.
The principal difficulty in albumenizing paper is to avoid the occurrence of streaky lines, which, when the paper is rendered sensitive, bronze strongly under the influence of the light. The writer believes these to be caused by a commencing decomposition of the animal matter composing the cells in which the albumen is retained and the best remedy appears to be to use the eggs quite fresh; the same object may sometimes (but not invariably) be attained by allowing the albumen to stand for several weeks until it has become sour; after which it will be sufficiently limpid to run through a filter.
In salting and albumenizing photographic paper by the formula above given, it was found that each quarter sheet, measuring eleven by nine inches, removed one fluid drachm and a half from the bath; equivalent to about one grain and three quarters of salt (including droppings). In salting plain paper, each quarter sheet took up only one drachm; so that the glutinous nature of the albumen causes a third part more of the salt to be retained by the paper.
Selection of the Paper.—The English papers are not good for albumenizing; they are too dense to take the albumen properly, and curl up when laid upon the liquid; the process of toning the prints is also slow and tedious. The thin negative paper of Canson, the Papier Rieve, and Papier Saxe, have succeeded with the writer better than Canson's positive paper, which is usually recommended; they have a finer texture and give more smoothness of grain.
To apply the albumen; pour a portion of the solution into a flat dish to the depth of half an inch. Then, having previously cut the paper to the proper size, take a sheet by the two corners, bend it into a curved form, convexity downwards, and lay it upon the albumen, the centre part first touching the liquid and the corners being lowered gradually. In this way all bubbles of air will be pushed forwards and excluded. One side only of the paper is wetted: the other remains dry. Allow the sheet to rest upon the solution for one minute and a half, and then raise it off, and up by two corners. If any circular spots, free from albumen, are seen, caused by bubbles of air, replace the sheet for the same length of time as at first.
The paper must not allowed to remain upon the salting bath much longer than the time specified, because the solution of albumen being alkaline (as is shown by the strong smell of ammonia evolved on the addition of the chloride of ammonium), tends to remove the size from the paper and sink in too deeply; thus losing its surface gloss.
Albumenized paper will keep a long time in a dry place. Some have recommended to press it with a heated iron, in order to coagulate the layer of albumen upon the surface; but this precaution is unnecessary, since the coagulation is perfectly affected by the nitrate of silver used in the sensitizing; and it is doubtful whether a layer of dry albumen would admit of coagulation by the simple application of a heated iron.
To render the paper sensitive.—This operation must be conducted by the light of a candle, or by yellow light. Take of