Every photographer is familiar with a yellow stain in the negative, caused by taking the plate from the fixing bath before it is thoroughly fixed. Belitski, the well-known photo-chemist, made some experiments recently to remove this stain, and succeeded very well. A slight stain can often be removed by placing the negative in the following solution: 5 parts alum, 100 parts water, 1 part potassium bichromate, 2 parts muriatic acid. After several minutes the negative turns yellow all through. It is washed now very thoroughly, exposed to sunlight for several minutes, and developed or blackened with the ordinary iron developer. When the stain is very intense, this remedy will not prove to be of any avail, and only by leaving it for 24 hours in the Lainer acid fixing bath he succeeded in removing the stain, and saving valuable negatives.
To transfer a print to wood, metal, glass, or even porcelain, it suffices to well clean the object if it is already polished, and to polish it in the contrary case, and then to spread over the surface a light coating of copal varnish. Then apply the toned and fixed print, still wet, and with a squeegee or printers' roller drive away the air-bubbles and excess of varnish; allow to dry for 3-4 hours. Then, rubbing gently with a slightly wet sponge, gradually remove the paper, the albumen film containing the image remaining attached to the glass by the varnish. A second coating of varnish will consolidate the whole. The only defect in this process is that it reverses the images. Those who operate on pellicle, or who practice phototype, and detach the gelatine pellicles, can make a reversed print, which, in this case, the process will correct. In this way it is possible to make very beautiful slides for the lantern, which are then to be painted for this particular application. Engravings may also be transferred in the same manner.
Dr. Miethe has been experimenting with Gaedicke's rapid dry-collodion plates, and has published the results, which are of considerable interest. Photographing a well-lighted view, and using a small stop, he exposed for four and two seconds respectively; using a large diaphragm, he took an out-door portrait in one second; copied an oil-painting, with the smallest opening. in four seconds and two seconds. The exposures proved to be: No. 1, overexposed; 2, about right; 3, slightly over; 4, over-exposed for the yellows;
5, correctly exposed. Development in all cases was completed with the properly-exposed plates in 30 seconds; with the others, in 40-50. He states that the orthochromatic effect obtained was very remarkable, the colours being reproduced according to their values better than they would have been on a plate treated with argentic erythrosine. The grain of the deposit appears under the microscope to be finer and more regular than that of gelatine plates.
Collodion, which is often slow in settling and clearing after preparation, may be entirely cleared by shaking it up with clean quartz sand. This carries the flocks and impurities to the bottom with it, and leaves the liquid above entirely clear.
Louis Bradfisch, an experienced manufacturer and user of aristotype papers, is convinced that the proper manipulation of these papers is by separate toning and fixing. After washing, he recommends a toning bath of gold chloride, soda acetate, and soda bicarbonate, and, when toning is complete, a combined hardening and fixing bath, which should be freshly prepared every day, and consists of 40 m. of acid soda sulphate solution and 2 oz. powdered alum in 20 oz. of water, to which 2 oz. of hypo are finally added. On immersion in this bath, the prints turn yellow, but assume the proper tone in 5-10 minutes.
The simplest toning bath for gelatino-chloride paper is that proposed by W. K. Burton, as follows: - Soda hyposulphite 3 oz., distilled water 20 oz., gold chloride 6 gr. with the addition of 3 gr. of lead nitrate to preserve the whites. The above bath tones slowly, and does not give the richness produced by the ammonia sulphocyanide formula, but will recommend itself to many on account of its simplicity.
A point of interest to users of celluloid films is that the various makers of these films coat the celluloid on different sides, some makers preferring the matt surface as a support for the sensitive emulsion, and others coating on the polished side. Of course, it behoves the user to familiarise himself with the method followed in the films he uses, as otherwise it will be an easy matter to place it in the holder "wrong side out."
(a) Steep in methylated spirit for half an hour, then dry quickly, and the frilling will almost entirely disappear. (6) Wash them in slightly warm water, harden the film with a strong solution of alum, afterwards drying them in front of the fire, and then, while still warm, apply common lubricating oil with a cloth. Make it a rule to thoroughly harden the negatives in alum after development, (c) Soak them in water and dry them with a moderately strong heat. Of course, the film must be hardened with alum previous to heating, or else the film will melt.
This paper is not only artistic, but costs little to prepare, both of time and money, and gives the most satisfactory results. By following closely the method given below, no one need go astray in its preparation.
One of the advantages of plain paper is its tendency to reproduce the finest detail, and to retain it during the subsequent toning and fixing. There have been many different formulae given for its preparation, but after exhausting a number of them, the method given below has given the best results. Let us first consider the things necessary for its preparation.
1st. The Paper. - While any kind of good strong white paper can be used, each giving a result peculiar to itself, it is economy to use the Saxe paper, which is easily procured at any photographic supply house.
2nd. The Sizing. - Almost all formulae advise gelatine, and while that will give excellent results, albumen gives clearer lights, and is much easier to coat.
Formulae and manipulations are as follows: -
The best results are obtained by fuming the paper for 20 minutes over ammonia, after which expose the same as albumen paper. After fuming, the paper is extremely sensitive, and had better be exposed in diffused light, unless the negative is very dense. It is better to print somewhat deeper than you care to have the finished print, as it loses density during the toning and fixing.