The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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Gelatino-Chloride
ally thin the frame should be placed in a weak light with opal or green glass over it, where the contrasts are greater use a stronger light; examine the print during the operation of printing in a very subdued light, and great care must be exercised that the paper does not shift whilst thus examining it, as it is very likely to do from its highly polished surface. As a preventive a pad of felt, or two or three thicknesses of stout blotting paper should be used. On the depth of printing depends to a great extent the tone of the resulting print; it is our practice when using this paper to carry the printing sufficiently far, so as to give the very highest lights a decided tinge, and, if black tones are required, till the highest lights are deeply coloured. After printing, the pictures should be carefully preserved from damp and light, and thus may be, if necessary, kept till some considerable number are collected, as they deteriorate but little by being kept a week or even longer. For toning, numerous baths have been suggested to give various tones ; most operators get into a particular groove of working special photographic papers, and from some consider-able experience I can recommend the following method of pro-cedure as conducive to good results. The first consideration is the negative; every negative is not suitable for this paper, though every negative will give a print on it. Those negatives which have very weak shadows and dense high lights give unsatisfactory results because there is a tendency in the paper to give an increased contrast; and for this very reason it is excep-tionally valuable for weak or somewhat thin negatives. For veritable ghosts, then, we can use green or yellow glass in front of the negative, or tissue paper or opal, so as to reduce the light, and print in weak diffused light. For stronger negatives we can, of course, print in stronger light. The question how far to carry printing is an important one, and a good deal depends upon the toning bath that is used. Practically it may be said that the paper should be exposed till there is a decided tinge on the high lights. Chloride paper may be kept some weeks before toning if actually required, but it is not advisable to keep it too long, or the whites suffer and it is more difficult to tone. We must now enter slightly into the chemical composition of gelatino-chloride emul-sions. All commercial papers, we believe, contain chloride of silver, with some organic salt, usually citrate of silver, with free nitrate of silver, and frequently citric acid. The nitrate and
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