If the ink hardens on the rollers remove it with lye or washing soda.

If you wish to interrupt the work, the plate must be washed with a wet sponge, to remove the preparation, and then dried with a cloth. On using again, apply No. 2, as before. If the plate has not been used for several days, apply both No. 1 and No. 2. Do not use woollen cloths.

The mixtures No. 1 and No. 2 are supplied with the press. {180}

Thus it will be seen that photographs may be reproduced by many processes and in quantities to accommodate all sorts of demands. As an averment of what the future holds, our book is brought to a close by the following quotation from a recent issue of a daily newspaper:

“Some time ago the Evening Post gave an account of a new process by which books were being reproduced in this country directly from photographic plates, and it was said that the field for such business would probably grow in proportion to the ease and certainty with which this kind of work could be done. Under this process the most important work issued so far has been seventeen volumes of the Encyclopædia Britannica, this production being sold at half the price asked for an American reprint already in the market, and at one-third of the price of the imported book. In order to make this reproduction, the sheets of the English volume are carefully photographed, and the glass negative placed over a thick sheet of specially prepared gelatine and exposed to the sun. Wherever the dark film upon the glass negative prevents the light from reaching the surface of the gelatine, this substance remains insoluble in water. Wherever the light penetrates, the gelatine undergoes a chemical change which makes it soluble. After an exposure to the sun or electric light for some minutes, the gelatine sheet is washed with water and the result is a plate in relief, every black line upon the glass negative being in high relief, and everything else washing away under the sponge.

“Until the last few years, it had been very difficult to get this relief sufficient to print from, but by improvements in the process effected by a number of different inventors, this result has been obtained. The gelatine sheet having been hardened, an electrotype is made from it which is put into the printing press. Owing to chance, the gelatine sheet itself was used one day for printing from directly, and it was found that a larger number of good copies could be made from the gelatine direct than from the hardest electrotype. The only drawback to the use of the gelatine plate itself in the printing press is its liability to crack, for no reason that has as yet been discovered. If some way is found of making the gelatine plate durable, it would be used entirely in place of an electrotype, as it costs almost nothing and can be made quicker than an electrotype.”

The way has been “found” and zinc etching is doing the work.

Finally, the essays of John Burnet, “On the Education of the Eye,” “On Composition,” and “On Light and Shade,” copies of which are hard to get for $100, have recently been reproduced by one of the processes given in this book, full size, and is sold at $4.00. There is a great future ahead for all process work.

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