Having thus given a short outline of the old-fashioned albumen process, we shall proceed with the details of the present system of working. In the first place, we commence with the preparation of the albumen itself - say 10 oz. This will require 12-15 eggs, according to their size. These, if available, should by preference be "new laid," though good French eggs will answer nearly, if not quite, as well. The eggs must be broken, and the whites carefully poured away from the yolks, keeping the latter in the shells. The germs should then be separated. To 10 oz. of the albumen, 1/2 dr. glacial acetic acid in 1/2 oz. water is added, and the whole intimately mixed by stirring with a glass rod. No attempt should be made to cause it to froth, which if done would give rise to trouble; 1/2 minute's stirring is all that is necessary. The acid will produce a precipitate, and render the albumen exceedingly limp. After standing a few hours, it is passed first through a piece of muslin to remove the coagulum, and afterwards filtered through a piece of sponge plugged in the neck of a funnel. After filtration, 40 minims of ammonia, . 880, is added, which causes the albumen to regain much of the viscosity the acid had destroyed.
Albumen thus prepared will keep quite good for many months, if preserved in well-corked bottles.
For use, the albumen is iodised by adding 1 dr. iodide of ammonia dissolved in 1/2 oz. water; sometimes 10-12 gr. bromide are also added. The albumen being .ready, we proceed to coat the plates. For this purpose some old iodised collodion is required. Any commercial sample that has been iodised for a length of time will answer, provided it yield an even and structureless film. If it be very old, it will possibly give a thin and tender film, in which case a little fresh pyroxyline must be added to give it body.
The glass plates being thoroughly cleaned and ready to hand, one is taken and coated with the collodion. After this has been allowed to set, the plate is immersed in a dish of common water, where it is allowed to remain, with occasional agitation, until all greasiness has disappeared. It is then rinsed under the tap and placed standing on a pad of blotting-paper to drain, while another plate is being collodionised. Now take the drained plate and pour over it, beginning at one end, a little of the iodised albumen. Flow it over in a wave, so as to carry the superfluous water before it, which, with the albumen, should be allowed to run off into the sink. Drain the plate somewhat closely, and apply a second lot of albumen, avoiding air-bubbles, and keep it in motion on the plate for 1/2 a minute or so in order that the albumen may penetrate into the collodion film. Then pour off into a measure, and stand the plates in a rack to drain. The second lot of albumen from one plate will do for the first application to the next, and so on.
By this means the albumen will be economised.
After a dozen plates have been coated, take the first one and hold it in front of a clear fire until it is dry, and so, in turn, with the remainder. When the plates are dry, it is a good plan to make them as hot as the hand can bear, for this treatment will prevent the films from blistering in the after operations, which otherwise they may have a tendency to do with some samples of collodion. Instead of drying the plates by the fire, some prefer to allow them to dry spontaneously; but, in this case, it will be found a good plan to make them thoroughly hot, for the reason just mentioned. Plates thus prepared will keep for years if preserved in a dry place. It need scarcely be mentioned that all these operations may be performed in open daylight.
Nitrate of silver . 2 oz.
Distilled water .. 1 pt.
Iodide of potassium. 5 gr. Glacial acetic acid
(52°) .... 2 1/2oz.
The method of mixing is as follows :--First, the iodide is dissolved in the water, then the nitrate of silver is added, and the whole is well stirred with a glass rod until the silver is dissolved. The solution is then filtered, and, finally, the acetic acid is added, when the bath is ready for use. The object of adding the iodide is to saturate the bath with iodide of silver, in order to prevent any of that salt being dissolved out of the film after it is once formed, which otherwise might happen. Sufficient of the solution to cover the plate to be sensitised is poured into an ordinary dipping bath. The plates are then immersed (with the precautions usual in the wet-collodion process) for a period of 1/2-l minute only. In summer, when the solution is warm, 30 seconds will be ample, and in winter the longer time may be allowed; but it should never be exceeded, as the sensitising takes place very rapidly, and a longer time than is necessary is liable to affect the plate injuriously.
By continual use, the bath will become discoloured, as does that employed for sensitising albumenised paper. It may, however, be decolourised by simply shaking it up with a little kaolin. If the bath be much used - or if it be allowed to stand in an open vessel when out of use - the addition of a small quantity of acetic acid from time to time will be necessary. Some operators prefer to employ a new solution for each batch of plates. In this case, the plates are usually sensitised in a flat dish, when, of course, a much smaller quantity of solution will suffice. When the plates are taken from the bath, they are placed in a dish of distilled water to remove the major portion of the fret nitrate, after which they are thoroughly washed under the tap to eliminate the remainder. They are then reared up on a pad of blotting paper to drain, and are afterwards dried.
The drying may be accomplished in any of the boxes used for gelatine plates, and, as the film is very thin, it does not retain much moisture; therefore the plates dry very much quicker than do gelatine. As many who do not possess properly-constructed drying boxes, or cupboards, may like to try the albumen process, it may be mentioned that one, suitable for the purpose, may be extemporised by taking an ordinary box, or packing case, and placing it in front of the lire for an hour or so to thoroughly desiccate the wood. In this case the plates arc placed on some dry blotting-paper, and in a few hours the plates will be perfectly dry, the moisture from them haying been absorbed by the desiccated wood. We have ere now used a common hatbox when anything more suitable was not at hand. It may be as well to mention here, for the information of those who have never prepared albumen plates, that it must not be expected that the films will be dense and creamy like those of gelatine, cr even of wet collodion, as they are always very thin and transparent.