THE BRITISH JOURNAL OF PHOTOGRAPHY. December 16, 1884, p.511
COLLODIO-ALBUMEN, OR TAUPENOT PROCESS.
AT our last meeting I was requested to read you a paper on the mode in which I work the collodio-albumen process. I do so this evening with great pleasure; but, in doing so, I wish you to understand that I do not profess to bring anything new before you. The process which I practice is the same, or nearly so, as that described some years ago by Mr. Mudd, whose excellent results you all know,, and which deserve of the process being more generally used. Most of you, no doubt, will be no wiser when I have done; but I think there are some new members amongst us who probably may derive some benefit.
Clean the plates with old collodion, and polish with a perfectly clean leather. Before pouring on the collodion warm the plates before a clear fire, two by two, and put the clean sides face to face together, so that the air, dust, and moisture may be excluded from the surface. Pile up the plates you intend to prepare for the time together, so that the whole may get equality warmed all over. Allow them to cool to nearly the temperature of the room, and then coat with collodion.
This precaution before the collodionising may seem superfluous to many of you, so may other little matters which I shall describe to you presently. I admit they may be sometimes; but they are not always. There are times when by warming these plates in the above manner it prevents blistering. I will not say that it always does, but it will do so very often; and it is by neglecting these precautions we get less regular success, and thus get disgusted with a process which, with proper care, will almost invariably give good results. The reason why I warm the plates is in order to get them, to be slightly above the temperature of the operating room, so that there is no chance of any moisture being condensed on the plate before the collodion is poured on; for I think such condensed moisture favours the formation of that great enemy in this beautiful process--blisters. I endeavour always to use a mixture of old and new collodion--not too thick. I always have, a mixture of about three parts of ether and one of alcohol at hand to dilute the collodion when it gets too thick. It should frequently be filtered or allowed to settle in a large stock-bottle, else bits are liable to get on the plates. Mr. Wilson's plan of filling a number of small bottles, and using only a part of each; is a very good one.
After pouring on the collodion allow it to set well, and not until then place it in the silver bath.
iodised and bromised by means of iodide and bromide of potassium or ammonium in the usual way.
Let-the plate remain in this bath about five minutes; then wash well in a dish and under a tap, .and plunge it with one sweep into a dish with salt and -water (say a -pinch of salt to half the dish full of water).If you do not do this with one sweep, you get a line across the plate to just where the liquid was allowed to stop. Then wash again, a little under the tap or a dish; drain â few moments whilst in your hand, pour over the albumen three or four times on and off front different corners:
The albumen is prepared as follows:--
Before adding the water to the albumen, dissolve in it the salts and the iodine (sufficient to make the solution a sherry colour), then add the ammonia: Beat the a whole up to a. thick froth either by means of a wooden fork, by shaking in a bottle with broken glass, or, best and easiest, with Noton's albumen beater. After allowing this to stand for some hours, pour off the clear liquid; which is now ready for use.
The plate, when coated with albumen is place in one corner and on clean blotting-paper, face side against a wall let it drain on this about a minute, and then change again for fresh clean blotting-paper. When, dry, or nearly so; bake the plate in your land before a hot bright fire. Other means, such as hot water pans or metal plates heated by a gas flame may be resorted to, but I prefer a clean fire. The preparation of the plates up to this stage may, if necessary, be conducted by diffused daylight, the film being rendered insensitive by the iodide in the albumen; but for my own part I prefer doing it in the dark room. I believe it prevents stains and dirty development.
The plates may now be stored away in boxes ready for the last sensitising, or be at once placed in the aceto-nitrate bath. If kept they should be warmed again just before sensitising.
iodised by means of iodide and bromide of potassium or ammonium.
Allow the plate to-remain in this bath about five minutes, and, after removing, wash it well under a tap or in several changes of water in a dish then place it against a wall on clean blotting-paper, which should changed when soaked up with the draining water. They will speedily dry, when they are a ready for exposure.
If the:plates are required to be kept for any length of time--say for months--a very excellent plan is to put their after the last washing in a dish with salt and water; then wash well under a tap; and lastly pour over a saturated solution of gallic, acid; and let them dry against the wall. This plan was practised last summer by M. Hebert and Mr. Young with great success. They affirm that plates heated in this manner are more sensitive; different opinions are, however; held on this point by others:
The exposure required for collodio-albumen plates varies of course, as in-all other processes; with the light and subject. I have obtained good pictures with an exposure of fifteen seconds, and I have given as much as two and three hours. But, on an average, an ordinary well lit-up subject requires from three to ten minutes for a stereoscopic picture. The right time can only be learned by experience.
The beauty of a Taupenôt plate over all other dry processes is in allowing itself to be humoured to an extraordinary extent in the development. Under or over-exposed plates, if treated with proper care, can always be brought out to give fair results. Although, of course, it is always desirable to give the proper exposure, yet there are times when one may err or not be able to give sufficient; it is in such-cases where the process is so valuable.
Hold the plate on a pneumatic holder, or place it on a levelling stand. Wet it all over, and pour the plain pyrogallic solution on and off until all the details are well out. If the plate be properly exposed, all will be out in a few minutes, but if under-exposed, it may be hours, or even days; and in such cases the plate may be placed in a dish with the pyrogallic solution--covering it up to avoid dust--occasionally examined.
When all the details are out, wash the plate, and add a drop or two of the silver solution to the pyrogallic. The details will now gradually get stronger and more defined by transmission. Add a few more drops of silver; and increase this more and more until the negative is of the strength required.
Plates-which have been salted and treated with gallic acid most have a drop or two of silver added to the pyrogallic from the commencement of the development, or soon after, to get the details out.
Fix in hyposulphite of soda, slightly acidified; wash well; dry, and varnish.
In conclusion; I should wish -to caution you to observe in all your operations the greatest cleanliness, and never allow, by-any chance, any foreign ingredient to intrude under, in, or upon, the surface of the sensitive film. Let the materials you use be of the best and purest qualities, and success is certain.H. PETSCHLER.
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