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October 2, 1891.] THE PHOTOGRAPHIC NEWS. 695 paper from the same negative—a group taken at the Society’s last outing at Greenwich. A question had been raised as to which process gave the more gradation, and he fancied that the colour to which silver prints were toned had something to do with the ability to see more in the shadows. The Chairman could certainly distinguish the gradation in the shadows better in the albumen than in the platinum prints. Whether that was due to the difference of surface as regards glass he was not prepared to say. Mr. P. Everitt said that Captain Abney had demonstrated that in the high-lights platinum gave truer gradation than silver. Mr. Beckett said that, as a platinum print dried, it seemed to lose gradation at the lower part of the scale. Mr. E. W. PARFITT showed some negatives, parts of which were covered with small transparent spots. He wished for the opinion of members as to their origin. The plates had been used in a hand-camera, and the spotty ones were usually those in the last sheath. Mr. A. Cowan thought that the spots were due to small air bubbles during development. Mr. Everitt had had similar spots when using pyro that had been preserved with sulphurous acid, and an alkaline car bonate was added. He attributed them to the evolution of carbonic acid gas. Mr. Cowan said that a trace of grease on a brush used to dust the plates might cause the developing solution to be re pelled, and so give rise to spots. Air-bubbles could always be ensured by using the same developer several times. Mr. Beckett said that the worst case of spots he had ever seen was caused by using a dish for the developer that had been previously used for mercury solution. Mr. TEAPE then showed a plate that had been exposed to openings cut in opaque paper. Part of the plate was unbacked, and part was backed ; one end with burnt sienna, and the other with caramel. There was no particular difference between the two latter portions, but, if anything, he thought the sienna had the advantage. The Chairman referred to experiments which he had’published last year, and which showed, when the action of light had been long enough to test the backings severely, that caramel had been decidedly more efficacious than burnt sienna. He was led to the use of caramel from its high refractive index. Experi ments of this kind, to be conclusive, required to be conducted with great care to ensure against some unreckoned cause creeping in. Mr. TEAPE said that as the backing was not quite dry when used, he had put black paper behind it. The Chairman could now account for caramel not having shown its superiority in the present instance. It was more tenacious of water than burnt sienna, and would therefore be moist when the latter had dried. Water had a low refractive index, and would diminish the efficacy of the backing con siderably. A question from the box was read : “ How can halation round a window in the negative be removed ? ” Mr. F. A. Bridge said that methylated spirit rubbed on with a piece of washleather would improve the negative by reducing density locally. When methylated spirit was insufficient, turpentine might be used to almost any extent. Another questioner wished to know whether members had experimented with the toning process for bromide prints described by Mr. Weir Brown. The Hon. Sec. had been using the method. He found the addition of acetic acid of the greatest use. Prints toned by the method, that had been in the Society’s charge for about three months, were then examined, and no falling off in appearance could be detected. The curator undertook to expose parts of each to a bright light for a lengthened period, and bring up the results to a future meeting. Mr. Weir Brown had some prints, parts of which had been exposed to the light since the beginning of the year, and he could find no change in them. Mr. F, H. Evans was elected a member of the Society. Hackney Photographic Society. The ordinary meeting was held on Thursday last. The pre sident was in the chair. Messrs. W. P. Dando and Augustus W. Wilson were nominated for membership. Being an evening set apart for the exhibition of members’ lantern slides, a number of ladies were present. The following members handed in slides, which were put through the lantern by the Hon. Secretary: Messrs. Sodean, Gosling, Dean, Carpenter, Dando, Poulson, Herbert Smith, Grant, Barton, and the Hon. Secretary. North Middlesex Photographic Society. Sept. 28th.—Mr. C. Beadle in the chair. Mr. Zimmer demonstrated the process of reproducing photo graphs in printing ink by means of the “ Photo-Autocopyist.” In working the process, it is necessary first to take a print from a negative upon a sheet of vegetable parchment coated with gelatine and sensitised with ammonia bichromate. The image is visible, and can be examined as in the case of an ordinary paper print. When sufficiently printed, the bichromate is washed out, the sheet dried, and stretched on the printing apparatus. It is then moistened with glycerine and ammonia, and inked with a greasy ink of a suitable tint. The image is masked to keep the margin clear, and, a piece of paper being laid on top, a print is taken in a copying press, and the latter portion of the process repeated as often as desired. The pre pared sheet may be stored away, and prints taken from it in the same or different colours at any future time. A number of prints were made and distributed among the members. The negative from which the sheet was prepared was shown, and it was seen that the prints did fair justice to it. A letter was then read from a member communicating a formula for a rapid printing paper by the blue process, which he had worked out. Prints were shown from dense and thin negatives, from which it appeared that the new paper was suit able for soft negatives. The formula was then made up and paper coated by it for members to test with the ordinary paper. Prints on various home sensitised papers, &c., were then passed round and criticised. Sheffield Camera Club. At the meeting on Wednesday evening in the rooms, New Surrey Street, Mr. G. T. W. Newsholme presided. Dr. Manton gave a lecture on “ Photogravure and Photo mechanical Processes Practically Illustrated.” The lecturer stated that the bulk of the processes now so much in vogue for the production of celebrated pictures, replicas of works of art, &c., depended on the actinisation of bitumen and chromated colloid compounds. After a brief description of the Woodbury- type process, full-detailed descriptions were given of the working of collotype, photo-lithography, and zincography, specimens of each process being produced and distributed among the audience. The somewhat complicated process of photogravure was lucidly explained, and illustrated by sketches on the blackboard, and experiments. The walls were covered with a very large number of beautiful engravings and photo etchings, untouched by hand from beginning to end. Another process briefly explained by the lecturer was chromo-collotype, for the production of pictures in colours, and a very beautiful specimen was exhibited. Votes of thanks were passed to the lecturer, and to Messrs. Pawson and Brailsford, the Meisenbach Co., and Mr. Sutton, for the loan of apparatus and specimens. Birmingham Photographic Society. September 2Uh.— Mr. W. J. Harrison, F.G.S., in the chair. After routine business, Mr H. S. Fry gave a demonstration in lantern-slide making. He compared collodion with gelatine, and, in the course of his remarks, stated that with gelatine the detail was more marked, the collodion generally tending to hardness. With gelatine various tones could easily be pro duced by increasing the exposure and using carbonate of am monia, and increasing the strength of the restrainer in the
