A Manual Of Photography

THE USE OF ALBUMEN ON GLASS PLATES AND ON PAPER. 285 White of Eggs, 2 fluid ounces and a half. Iodide of Potassium ... 56 grains. Bromide of Potassium . . . 15| „ Chloride of Sodium ... 4„ M. Le Gray, in his memoir, gives the following general directions:— Pour the solution into a dish placed horizontally", talcing care that there is no froth; then take the paper that you have chosen, and wet it on one side only, beginning at the edge of the dish which is nearest to you, and the largest side of the sheet, placing the right angle on the liquid, and inclining it towards you; advance it in such a manner as to exercise a pressure which will remove the air-bubbles. Place before you a light, so as to be able to perceive the bubbles, and to pusle them out if they remain. leet the leaf imbibe for a minute at most, without touching it; then take it up gently, but at once, with a very regular movement, and hang it up by the corner to dry. You prepare thus as many leaves as you wish in the same bath, taking care that there is always about a quarter of an inch in depth of the solution in the dish ; then place your sheets (thus prepared and dried) one on the other between two leaves of white paper, and pass over them several times a very hot iron, taking out a leaf each time : you will thus render the albumen insoluble. The iron should be as hot as it can be without scorching the paper. Then make use of this negative paper exactly like the first paper named ; only great attention must be observed that the immersion in the aceto-nitrate bath is instantaneous, and that the air-bubbles are immediately driven out; for every time you stop you will make stains the same as on glass. It is also necessary to heat moderately the gallic acid. One of the best services rendered by the albumen to photo- graphy is, without doubt, its application to the preparation of the positive paper, to which it gives a brilliancy and vigour difficult to obtain by any other method; which is prepared thus:— Take white of eggs, to which add the fifth part by volume of saturated solution of chloride of sodium; then beat it into a froth, and decant the clear liquid after it has settled for one night. With this the paper is first washed, and then with a strong solution of nitrate of silver.