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Reproducing Drawings

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REPRODUCING DRAWINGS The question of the method of reproducing drawings is an important one as to cost and time consumed. New methods are being adver tised on the market every day.

Blue-Printing.

The blue-print process is the commonest, and generally speaking the cheap est. There is a chemically prepared paper which is sensitive to the light. The paper is treated with a solution of citrate of iron, ammonia, and red prussiate of potash, and is placed in a dark room to dry. The drawing has previously been prepared on tracing cloth or paper. When the blue-print paper is dry, place the drawing, face down, on a sheet of glass, usually held in a wooden frame; over this, lay the blue-print paper, with the sensitive side down; over this, place a layer or two of soft cloth similar to Canton flannel, and over this place a board backing.

Turn the frame over now, and expose to the sunlight for a few minutes, depending upon the intensity of the sunlight. After exposure, remove the blue-print paper, which has turned to a dark bronze color, and place it in a tank of water. Gradually the print comes out in white lines, leaving the background blue. These white lines were directly under the ink lines of your drawing, and the stuff therefore could not attack that portion of the paper. Hence the water washed off the blue-print solution, leaving the white paper.

A little experience will soon teach how long to expose in different kinds of weather. Prints may be made on cloudy days, and have some times been made even during a mist. The expos ure, of course, must be much longer on such days. The prints from such exposures are not so clear, distinct, and "sharp-cut" as those made on bright days. When possible, avoid making blue-prints on dark days, if you expect the best results.

Paper for blue-printing can be procured ready to use, from dealers all over the country, at a nominal cost. This is machine-prepared, and is more satisfactory than home-made.

Blue-prints are hard on the eyes, and, having a blue background, cannot be dimensioned, noted, or to any great extent changed. Should small alterations be necessary on the blue-print, use a solution of common soda and water with a pen. This is not very satisfactory, but in cases

where changes are necessary it will do.

White-Printing. From working drawings, white prints can be made. This kind of print is just the reverse of the blue-print. Here we have blue lines on a white background. In order to make white prints, a negative first has to be made from the drawing. The paper used for the negatives is specially prepared and exposed and washed in the same way as blue-prints. When washed and dry, it is a real negative, on which a11 pencil lines are white and the background is black so as to exclude the sun—all the reverse of the drawing. This negative is then used by placing it over regular blue-print paper. The sun passes through the white lines, and is excluded from the rest by the black background. Upon washing the blue-print paper, the lines having been exposed to the sun are changed to blue; and the background, not having the sun on it, is washed off, leaving the white paper.

This process makes a much better looking drawing than a blue-print, and is not so hard on the eyes. The cost is a little higher, on account of the negative; but after the negative is made, the cost is the same as for blue-prints.

Aligraphy. Another process, known as Aligraphy, has been patented. By it, drawings can be reproduced on linen or paper, and the lines are practically as black as the original. They closely resemble etchings. For very fine work, this process makes splendid reproduc tions; but it is more expensive than any of the processes above mentioned.

Hectograph Process. Another common method of reproducing drawings is the hecto graph process. This consists in making the drawings with suitable aniline inks, and then placing them face-down on a gelatine pad. After being in contact for about two minutes, they are removed, and blank paper is brought in contact with the pad, being in turn removed. It will be found to give a complete drawing similar to the original in scale, color, etc. Upwards of thirty five copies may be taken off, depending upon the intensity of the original.

Reproducing Drawings
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