The Dictionary Of Photography

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

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Photogravure
third the quantity of distilled water to it and allowing it to dissolve as much as possible, and then diluting it with distilled water till it marks 45o Baume, 400, 380, 35o, and 270 Baume. These five solutions are carefully prepared of the above strength, or, in the absence of a hydrometer, the solutions may be made up of the percentage strengths which correspond to the above, 47, 41, 38, 35, and 27. These must be the percentage solutions, and can be made as follows, assuming that we require 10 ozs. of solution : -
We require a transparency of the negative to be reproduced. This transparency should be made on an ordinary dry plate, and should be soft and delicate, more approaching the ordinary negative than lantern-slide characters. From this transparency we must prepare a negative in carbon. Either transparency or standard brown may be used. The negative must be thin, and quite free from any deposit in the deepest shadows. The dusting box must be lined with varnished paper, and the asphalt sifted through fine linen. The copper plates should be obtained already bevelled and polished, and merely require cleaning with weak caustic potash solution and then with ammonia, and washing, whitening, rinsing and drying. The plates are now ready for graining. To do this the box, con-taining from one-half to a pound of powder, is rather slowly revolved for about three times, and then brought to a stand with the door at the bottom. It is allowed to rest for one minute, and then the copper plate, placed on a larger piece of plate-glass, is placed on a box or piece of wood on the bottom of the box inside, the door closed, and the dust allowed to settle for about five minutes, and then taken out and examined to see whether enough dust or grain is on it. How much grain to lay is a matter of experience. A dark subject requires not only more grain, but a coarser grain, than a lighter subject. For ordinary subjects the best way is to allow the dust to settle for about one minute, and then to leave the copper plate in for ten minutes. Having grained the plate, the next thing is to fix the grain. This
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