Scientific American Supplement, No. 303, October 22, 1881 by Various
page 42 of 138 (30%)
page 42 of 138 (30%)
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contact with the negative and exposed for a few minutes, after which it
is immersed in water, squeegeed down upon a glass plate, and developed with warm water in the way so well known to carbon printers. The result is a transparency which, owing to having received a sufficient exposure, should show every detail of the negative. The nature of the tissue employed for such a purpose must be such as to give no strong contrasts, but everything reproduced with soft and fine gradation of tone. The transparency thus obtained forms the _cliche_ by which the negatives are subsequently made; and a negative of any size may be obtained by the camera on wet or dry plates. The transparency must, of course, be pointed to the sky and the light transmitted through it, no other light being allowed to reach the lens except that which passes through the carbon transparency. Care must also be taken that the transparency is _uniformly_ lighted. If it is not possible to obtain a northern light, which is best, a reflector of white paper or card may be used which must be sufficiently large and placed at an angle of about forty-five degrees to the transparency. If the repeated negative is to be of the same size as the original it may be readily produced by repeating the operation of printing on carbon tissue, using the transparency in place of the negative, or using a dry plate in place of the tissue. But on the whole I have satisfied myself that the best results are to be obtained by the first method. There is a greater softness in the latter method, but a greater character and similarity to the original in the former method. There is no doubt that the use of the carbon transparency removes the hardness and riffidness of the outlines peculiar to the older method of a collodion transparency, while with carbon as the medium it is difficult for any but the most experienced eye to distinguish the copy from the |
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