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Transparencies

glass, paper, plate, negative, sheet, transparency and print

TRANSPARENCIES are usually made in the same manner as lantern slides by exposing to gas or lamp light. In printing, a mat or mask of opaque paper should be used, so as to leave a narrow margin of clear glass outside the picture. Trans parencies can be made on any plate, either rapid or slow, the latter being preferred. As in all contact printing both the nega tive and the plate should be carefully dusted before placing in the frame: and it is well to place a dark cloth above the plate to avoid any reflected light from the back of the printing-frame. A slow plate, of sensitometer equal to a Carbutt B 16, requires an exposure, at eighteen inches from an ordinary gas-light, from two to six seconds, according to the intensity of the negative; while a quick plate of sensitometer 25, needs from one-eighth to one or two seconds. As soon as the exposure is made the plate can be taken from the printing-frame and developed imme diately, or placed in a light-tight box and developed later with others.

The transparencies should be developed in the same way and after the same formula as the lantern slides, but the development should be carried a little further and be made somewhat intense. When finished the transparency should be backed, the film inside, with a sheet of ground glass or imitation ground glass, which we shall describe how to make in our formulas hereafter. Then it can be bound at tbe edges with paper, or placed in metallic frames kept by all dealers.

Some dry-plate makers prepare a special plate for transparen cies, having an opal or ground-glass finish on one side, which requires simply a sheet of plain glass on the film side to protect it from injury.

A very neat way to make transparencies is to print them by contact and gas-light on Eastman's transferotype paper. These require an exposure of from fifteen to forty seconds, and should be developed with the h,ydroehinon, lantern slide developer. After development they should we well washed, then fixed in hypo, and washed again. When washed the print should be laid face down on a sheet of clean, clear glass, of the proper size, and the water removed with a rubber roller or squeegee. The glass and the print should then be laid on some flat surface, with a sheet of blotting paper on the back of the print, and left to dry under pressure. When dry the print will adhere to the glass, and, if desired, the paper can be removed as described in the directions accompanying the package of transferotype paper, and backed with ground glass.

We think, however, the better way is to leave the paper on, and simply back it with plain glass, as the paper is a most excel lent substitute for the ground glass.

It is sometimes of advantage to duplicate a negative, which is done by first making a transparency, which is a positive, and from that, in the same way, a second transparency, which will be a negative. In the same way a new and stronger negative can be made from a very weak one.

Sometimes one may have occasion to make a transparency for enlargement from a negative which may be very intense in cer tain portions, while very thin in others. To correct these in equalities in the transparency make a mask of thin, white"paper of the proper shape to cover the thin portion, which c,an be sup ported on a pasteboard frame, the opening in which is the size of the negative. During the printing, this mask, by means of the stiff frame, can be held close to the printing-frame, so as to shield the light from the thin parts, allowing it to act on those which are too intense, to bring out detail, the mask, .of course, being kept constantly moving. A new negative can be printed by con tact from a transparency so made, in which the original defects of local intensity or thinness will be found corrected, the result being better than if resort were had to chemical means.

Very pretty blue transparences can be made in the following way: Dissolve fifteen grains of sheet gelatine, cut into fine pieces, in an ounce of hot water. When this is cold, pour a por tion of it on a sheet of clean, glass, tilting this to allow the liquid to spread over the surface, and stand on edge to dry. This can afterwards be sensitized with the same solution we use for making blue paper by flowing it over the plate, and allowed to dry by standing on edge.

The printing and developing can be done in the same way as with blue paper Before printing, as the glass cannot be re moved from the frame to examine it, in order to know the time required for the exposure it will be necessary to make a blue print on paper from the same negative, and take note of the time required for that.