(6) Permanently moist copying paper. A perpetually damp copying paper, always ready for use, is described in the Paper Trade Journal. It is prepared by dissolving 1 lb. of chloride of magnesium in a moderate quantity of warm or cold water - about 1 lb. When dissolved, apply this solution with a brush to ordinary copying paper, whether in book form or otherwise, or preferably by means of cloth pads saturated with the liquid, then placcthese pads between any suitable number of leaves; apply pressure, at first very moderate, until the absorption by the paper is complete; then remove the cloth pads, and apply with the press a strong pressure; it is then ready for use.
Paper prepared by this process will remain permanently moist under ordinary temperature, and if made dry by an extraordinary heat, will regain its moisture upon being subjected to the common atmosphere.
One advantage of this method is, that the sheets of paper will not adhere to each other, as is frequently the case when the paper is prepared with compounds containing glycerine, etc. The above process is patented.
(7) Any kind of opaque drawing paper in ordinary use may be employed for this purpose, stretched in the usual way over the drawing to be copied or traced. Then, by the aid of a cotton pad, the paper is soaked with benzine. The pad causes the benzine to enter the pores of the paper, rendering the latter more transparent than the finest tracing paper. The most delicate lines and tints show through the paper so treated and may be copied with the greatest ease, for pencil, Indian ink, or water-colours take equally well on the benzinised surface. The paper is neither creased nor torn, remaining whole and supple. Indeed, pencil marks and water-colour tinting last better upon paper treated in this way than on any other kind of tracing paper, the former being rather difficult to remove by rubber. When large drawings are to be dealt with, the benzine treatment is only applied in parts at a time, thus keeping pace with the rapidity of the advancement of the work, When the copy is completed, the benzine rapidly evaporates, and the paper resumes its original white and opaque appearance without betraying the faintest trace of the benzine.