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over them gently at first, and then more strongly, to bring the two surfaces into intimate contact in every part. This, and all subsequent operations, may be carried on in an ordinary lighted room, as the tissue loses its sensitiveness whenever it is wet. From the same cause the printing action (which, as I said, continues after the tissue has been removed from the frame) is stopped, so that, if any prints which have been fully printed cannot be developed at once, it is better to squeegee them, when they will keep for a couple of days or so. The development is effected by soaking the tissue and transfer, which are now in close contact, in water from 100° to 120° Fahr. In a short time the coloured gelatine will be seen oozing out from the edges of the tissue ; it must then be taken hold of and drawn carefully off under water, leaving on the trans fer paper a dark soluble slimy mass, under which lies the insoluble picture. This is allowed to soak in the water for a few minutes, and then the superfluous mass of gelatine and colour is removed by splashing the water over it. If the print, when partly developed, shows signs of being light, the water must be cooled down ; or if it is still too dark when all the superfluous matter has been washed away, it can bo lightened by prolonged soaking in water about 150° or 160° Fah. If it is very obstinate, a little carbonate of soda or ammonia will reduce it to a proper depth, unless it has had about double the exposure which was necessary. When the print has been fully developed, allowing for a slight increase of depth after drying, it is removed into clean cold water, and allowed to stand for five minutes at least, to remove as much of the bichromate as possible. It is then placed in a bath of alum composed of one pint of alum in fifty pints of water, and allowed to remain about ten minutes; then well washed in clear water, and hung up to dry. Photographs which are intended as illustrations for books, or, indeed, any photographs which have to be mounted on paper, can be developed on the paper direct, and thus get rid of the other wise inevitable cockling. The only precaution required to be taken is, to have a square safe-edge on the negative. This is most easily done by pasting strips of black or yellow paper round the negative. Carbon prnts on opal glass are done by the single transfer pro cess, no preparation of the glass being required; it is merely washed, and the tissue squeegeed on it as on paper. The greatest objec tion to the single transfer process is, that a reversed negative is required ; whereas double transfer prints can be done from an ordinary negative. To my mind, this is the only advantage which it has over the single transfer process. The double transfer process is as follows : Having got our print as for single transfer, it is developed on either white smooth glass, or, if a matt surface is required, on finely-ground zinc. The glass is prepared, after being thoroughly cleaned, by first rubbing the plate well with powdered French chalk, after which all the loose powder is dusted off ; it is then coated with plain enamel collodion. As soon as this has set (say in two minutes) it is placed in a dish containing pure water, not too cold, till all the greasiness has dis appeared. The plate can now either be used at once in its wet state, or can be dried, and damped again when required for use. To prepare a zinc plate—or ground glass, which answers the same purpose, but which has not such a fine grain—they must be rubbed with a solution of one part each of wax and colophony or pure resin in 50 parts of turpentine or benzine. The mixture is rubbed on with an old linen or flannel cloth, which acts best after it has been repeatedly used, as too new a cloth takes too much wax off the plate agai n, in which case the print sticks or gets a grey tone from the zinc. Having the plate prepared, the printed tissue is squeegeed on it, and it is developed the same as a single transfer print. More care must, however, be taken in the development, as the collodion film is easily broken, and the print easily scratched. It is then washed, fixed in alum, and allowed to dry. Any re touching which the print requires must be done at this stage, either with oil-colours and brush, or dry powder colour and a leather stump. The picture is now ready to be transferred from the glass or zinc plate to paper. For this purpose the double transfer paper I have already described is used. A piece is cut rather smaller in size than the plate on which the print is lying, and is softened in water from 100° to 110" F. As soon as the gelatine feels softened, the paper is placed in cold water, and kept there until wanted for use. The plate containing the print is now dipped for an instant into cold water; the softened transfer paper is then laid (gelatine side downwards) over the print. A sheet of india- rubber cloth is then laid over the transfer paper, and the surface of the latter is brought into close contact with the print by means of a firm pressure in all directions from the squeegee. This is then allowed to dry perfectly, when the print can easily be stripped from the plate. The only other subject which I intend to speak a word about is the production of transparencies either for enlarg ing or making reversed negatives from, or for the magic lantern. In the preparation of the tissue more care must be taken, espe cially in the grinding of the colour, which must also be filtered through cotton-wool. The proportion of colour to the gelatine is also different, about 7 instead of 3} per cent. It is sensitized and printed in the same way' as an ordinary print. A trans parency for the lantern is printed about the same depth as an ordinary print, but a transparency for making negatives from requires almost double as much printing. After the tissue is printed, it must be coated with thin enamel collodion, about half the ordinary thickness, and allowed not only to set, but to dry. The glass plate is prepared by coating it wet with a solution of gelatine, the same as is used for single transfer paper, or by coating it dry with a very thin solution of gelatine in acetic acid and alcohol, about half-ounce of gelatine to ten ounces of solu tion. The last is much better, as the coating of gelatine is extremely fine and thin. The tissue is then squeegeed and deve loped in the ordinary manner. The negative from whicha lantern transparency is printed should be rather dense or hard, in order to give a brilliant effect on the screen ; but if the transparency, after development, proves too thin or weak, it can be intensified in quite a number of ways. I think the best way to intensify lantern transparencies is by flowing ordinary writing ink over them. The ink stains all the gelatine, and of course the deep parts which have most gelatine get stained in a proportionate degree to the thin parts. Transparencies for making negatives from are intensified by a solution of permanganate, which acts in the same way as the ink, but which has not such a pleasant colour for the lantern. In making transparencies for multiplying or making reversed negatives from, any saving, double printing, or other dodging can be done, so that when it comes to printing off copies there is nothing to do but fire away. The printing-in of clouds, for instance, when a large number of prints are wanted could not be done any other way. It is rather difficult to print in clouds or backgrounds, as you cannot see the picture. It is done in this way : when the landscape is printed, the frame is opened, taking care not to move the tissue on the negative; it is then turned up, and powdered French chalk painted on the negative. The tissue is then pressed on the negative, and a copy of the outline is obtained. The cloud is then allow ed to print in slightly over the edge of the landscape. DRY PLATES AND THEIR DEVELOPMENT. BY B. TAAIKTN.* Those of us who had the pleasure of hearing Mr. M’Kean’s paper read at the last meeting of this Society, and of witnessing his practical demonstrations, could not fail to be very much interested, and the subject of dry-plate development being one of much importance, it was decided to devote a portion of this evening to its consideration. I was asked by our worthy Secretary to lead the discussion, and consented to do so; but as Mr. M’Kean in his opening remarks alluded to one or two things about which various opinions have been expressed in the journals and elsewhere, I would like just to notice them before proceeding with the subject specially recommended for our consideration. In the first place, Mr. M’Kean speaks of uncertainty in work ing with commercial gelatine plates. As I have proved to my own satisfaction, I would like to prove to yours, that un certainty need not exist, and if we had ever before possessed as reliable a process as the gelatine-bromide, I would not take exception to his remarks. If we compare the gelatine process with the wet collodion, I think that most will allow that the silver bath is a constant source of anxiety to whose who use it; if working well to-day, you cannot be sure that it will work as well to-morrow ; whereas, get a batch of gelatine plates from a good maker, and give them proper treatment, and such uncertainty need never trouble you. We get through gross after gross of plates, and I seldom trouble to ascertain when we are finishing the one batch or beginning the new, as they are all so much alike. Only this afternoon I exposed a dozen plates (of a kind I have not been accustomed to) on as many different copies, deferring the development until all were exposed. All proved satisfactory • Read before the Edinburgh Photographic Society.