To size poor drawing paper, take one oz. of white glue, one oz. of white soap, and one-half oz. of alum. Soak the glue and soap in water until they appear like jelly, then simmer in one quart of water until the whole is melted. Add the alum, simmer again and filter. To be applied hot.
To Prevent Alterations in Writing.
The following process of preparing paper will prevent alterations in writing:—Add to the sizing 5 per cent of cyanide of potassium and sulphide of antimony, and run the sized paper through a thin solution of sulphate of manganese or copper. Any writing on this paper with ink made from nutgalls and sulphate of iron, can neither be removed with acids nor erased mechanically. Any acid will change immediately the writing from black to blue or red. Any alkali will change the paper to brown. Any erasure will remove the layer of color, and the white ground of the paper will be exposed, since the color of the paper is only fixed to the outside of the paper without penetrating it.
To Prevent Gummed Paper From Cockling.
It is well known that paper, when gummed, often cockles. To remedy this a little glycerine or sugar should be added to the gum.
Copying Drawing in Color.
The paper on which the copy is to appear is first dipped in a bath consisting of thirty parts of white soap, thirty parts of alum, forty parts of English glue, ten parts of albumen, two parts of glacial acetic acid, ten parts of alcohol of 60°, and 500 parts of water. It is afterwards put into a second bath, which contains fifty parts of burnt umber ground in alcohol, twenty parts of lampblack, ten parts of English glue, and ten parts of bichromate of potash in 500 parts of water. They are now sensitive to light, and must, therefore, be preserved in the dark. In preparing paper to make the positive print, another bath is made just like the first one, except that lampblack is substituted for the burnt umber. To obtain colored positives the black is replaced by some red, blue, or other pigment.
In making the copy, the drawing to be copied is put in a photographic printing frame, and the negative paper laid on it, and then exposed in the usual manner. In clear weather an illumination of two minutes will suffice. After the exposure the negative is put in water to develop it, and the drawing will appear in white on a dark ground; in other words, it is a negative or reversed picture. The paper is then dried and a positive made from it by placing it on the glass of a printing frame, and laying the positive paper upon it, and exposing as before. After placing the frame in the sun for two minutes, the positive is taken out and put in water. The black dissolves off without the necessity of moving back and forth.