THE PHOTOGRAPHIC NEWS, February 22, 1861, p.87
THE ALBUMEN NEGATIVE PROCESS.
As this process appears just now to be exciting some attention, and, to judge by our correspondence, several of our subscribers appear anxious to give it a trial, we think that a succinct and detailed account of the various manipulations will prove acceptable to those to whom the process is not familiar--to whom the mere statement of formulae recently. given by Mr. Richards may be insufficient.
In a former volume will be found a very full description of an albumen process, by Mr. Negretti; but, as he himself remarks, his method is little suited to amateur use. We shall now select for description a modified process introduced by Mr. Whipple, by which, from its extreme simplicity and certainty, we think the humblest skill may produce good pictures.
1.--Take a pound of lump sugar, and dissolve it in half a pint of clean rain-water, then boil the solution for five minutes, and pour it into a stock-bottle for use.
Select always the largest eggs, and as fresh as they can be had. If it is intended to work upon stereoscopic plates, one or two eggs will be quite sufficient to use at a time, as, although the mixture will generally keep for a month or more, it sometimes becomes deteriorated much sooner; it is, therefore, advisable not to tax its keeping qualities too severely.
The mixture for coating the plates consists of--
The iodide and bromide should first be dissolved in the water, then added to the other ingredients, and the whole placed in a six or eight ounce bottle, which must be shaken vigorously until it is all reduced to a froth. This must be laid aside for at least forty-eight hours, when it should be filtered into a clean bottle, and a small piece of camphor added.
To coat the plate, prepare two small measures, and a funnel that will stand conveniently in them. Throttle the funnel lightly with a piece of sponge, or wool, and filter through it, into one of the measures, sufficient albumen to cover the plate with. The glass plate, made scrupulously clean, and placed in a pneumatic holder, may now be coated by pouring on the albumen in the same way as collodion, the excess being poured off into the second measure. The first measure must be used exclusively for filtered albumen, by which precaution, all danger from bubbles or dirt -may be avoided. The same albumen may be again filtered into the, first measure for the next plate, and so on till the whole is used up; or, if all be not required at one time, it may be put back into the bottle for a future occasion.
After draining the albumenized plate about ten or fifteen seconds, it must be laid for a minute upon a levelling stand in order that the film may equalize itself upon the glass:
then, holding it at the corners between the finger and thumb, it must be dried over the flame of a spirit lamp, or gas jet, beginning at the corner opposite to that where the albumen was poured off. The plate should be kept, during this operation, constantly moving, that the film may not be burnt, anti it must he held slightly inclined so that the excess may drain off from the same corner as before, which must be wiped from time to tune upon a piece of clean filtering paper. When the plate is quite dry, which may be ascertained by touching lightly the corners, it must be laid aside for a few minutes until it is sufficiently cool to be placed in the bath without jeopardizing the glass--but it is best not to let it get quite cold; when ready, plunge it with one movement into a bath of--
The plate should remain in this bath about half a minute after which it must be well washed with common water. This may be done either with a washing bottle or under a tap, or the plate may be placed in a pan of clean water for a short time, and moved up and down with a horn or silver hook. The object of this washing is to remove the free nitrate of silver from the film, which tends by its presence to promote spontaneous decomposition in the dried plate, and thus injure its keeping qualities, while it does not add to its sensitiveness. It is desirable, therefore, that the whole of it should be removed, so, after a thorough washing, the plate must be placed in a. bath or pan of--
and left in this solution for at least a minute, that any remaining nitrate of silver may, be converted into a chloride.
A thorough washing with common water, to remove the excess of the saline bath, completes the preparation of the plate, which may be left to dry spontaneously, or dried before a fire without flame.
We are not of those who decide upon the merits of a process by the number of plates that can be prepared by it in given time; but it will be seen that the "albumen" process may vie with most for the simplicity of its formulae and manipulations.
The time of exposure will, of course, depend upon circumstances, but, albumen plates will generally be found to require a rather longer exposure than collodio-albumen. This, however, is. a point that the operator can best decide by experiment. Of the two faults, it is better to over-expose than under-expose, as. the former may be corrected in, developing by using weaker solutions; but the prolonged development necessary to bring out the dark parts of: an under-exposed picture is apt to mar the beauty of the half-tints for which this process is so justly celebrated.
The best developer for albumen is without doubt gallic acid.: it is also easier of application than either pyrogallic or iron, for its effects are produced more slowly, and the plates, therefore, do not require so much personal attention. Having well cleaned a glass or porcelain pan (gutta-percha will not do for this part of the process) with cyanide of potassium, pour into it sufficient just to cover the plate of a saturated solution of gallic acid, which will be found to he nearly--
to every Ounce of this add ten minims of silver solution;
cover the pan. over to exclude dust and light. In about a quarter of an hour the picture will begin to appear, and in two hours or less, according to the amount of exposure, all the details will be visible. If desirable, a little more silver may be added now; but a plate that has had a proper exposure should not need it; in no ease should any more silver be added until all the required detail is well out, otherwise the other portions of the picture will exhibit too great a contrast and appear hard.
Should it be found difficult to make the water dissolve the quantity of gallic acid we have named, gentle heat may be used, which will hasten the operation. Indeed, we mentioned the necessary strength of the solution purposely, because persons who are not accustomed to use this salt are apt to mistake the point of saturation. The gallic acid may be employed hot if it be wished to shorten the time of development.
We should notice that a photographic picture upon albumen obstructs chemical light in a much greater degree than one of a similar apparent density upon a collodion film, and therefore the development must be stopped at a point less dense in appearance than would be considered desirable for a collodion negative.
The ordinary pyrogallic acid solution may also be employed with albumen in the usual way, but it is questionable whether the results equal those produced by gallic acid. The strength of the pyrogallic solution should be--
Place the plate on a levelling stand, and thoroughly moisten the surface with clean water. Having, drained the plate, pour on the pyrogallic solution, with an addition of five minims of ,the silver solution (6) to every drachm of developer. In about five minutes the picture will begin to appear. As with gallic acid, no moisture should be added until all the details are quite clear, and only then if really necessary. The solution generally remains clean until the development is complete; but should it discolour much it should be renewed.
The picture must be fixed with hyposulphite of soda in the usual manner. Unless a, very large number of positives are required to be printed from it, the negative will, not require to be varnished, as the, film is very hard, and the picture well in it.
We think the above description will enable any of our readers who may wish to try this process to do so with success, for it is very uniform in its results when worked with ordinary care. It. has at least this advantage that the raw material albumen is attainable in its greatest perfection by those who live away from the chief sources of collodio; and to, these it may be worth serious attention.
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