The most successful operators with waxed paper have been M. Le Gray on the Continent, and Mr. Fenton in England. In a work lately published by Le Gray, he has entered into the question of the physical agencies which are active in producing the chemical changes on the various preparations employed. Throughout the essay, he evidently labours under an entire misconception of the whole of the phenomena, curiously enough giving a false interpretation to every fact His manipulatory details are very perfect, but his scientific explanations are only so many sources of error.
This process divides itself into several parts, waxing the paper being the first. For this purpose he takes the paper prepared by Lacroix d'Angoulême, or that of Canson brothers of Annonay. A large plate of silvered copper, such as is employed for the daguerreotype, is obtained and placed upon a tripod, with a lamp underneath it, or upon a water-bath. The sheet of paper is spread upon the silver plate, and a piece of pure white wax is passed to and fro upon it until, being melted by the heat, it is seen that the paper has uniformly absorbed the melted wax. When this has thoroughly taken place, the paper is to be placed between some folds of blotting-paper, and then an iron, moderately hot, being passed over it, the bibulous paper removes any excess of wax, and we obtain a paper of perfect transparency.
In a vessel of porcelain or earthenware capable of holding 5 pints and a quarter of distilled water, put about 4000 grains of rice, and allow them to steep until the grains are but slightly broken, so that the water contains only the glutinous portion. In a little less than a quart of the rice solution thus obtained, dissolve :—
Sugar of Milk...... 620 grains.
Iodide of Potassium .... 225 „
Cyanide of Potassium ... 12 „
Fluoride of Potassium ... 7 „
The liquid, when filtered, will keep for a long time without alteration.
When you would prepare the paper, some of this solution is put into a large dish, and the waxed paper, sheet by sheet, is plunged into it, one over the other, removing any air-bubbles which may form. Fifteen or twenty sheets being placed in the bath, they are allowed to soak for half an hour, or an hour, according to the thickness of the paper. Turning over the whole mass, commence by removing the first sheet immersed, and hooking it up by one corner with a pin bent in the shape of the letter S, fix it on a line to dry, and remove the drop from the lower angle by a little bundle of blotting-paper. M. Le Gray then remarks that French and English paper should never be mixed in the same bath, but prepared separately, as the "English paper contains a free acid, which immediately precipitates an iodide of starch in the French papers, and gives to them a violet tint." The paper being dry is to be preserved for use in a portfolio.
Make a solution of:
Distilled water...... 2325 grains.
Crystallized nitrate of silver . . 77 1/2 „ and when this is dissolved, add of Crystallized acetic acid 186 grains.
Papers prepared with this solution will keep well for a few days. M. Le Gray, however, recommends for his waxed paper, and for portraits, that the quantity of nitrate of silver be increased to 155 grains, and that it should be used moist.
The method of preparing these papers is to float upon an horizontal plate of glass either of the above solutions, and taking a piece of the iodized paper, to carefully place it upon the fluid, taking great care that no air-bubbles interpose. The paper must remain a short time in contact with this sensitive fluid until chemical combination is effected. Four or five minutes are required for some papers, and eight or ten seconds are sufficient for other kinds. When a violet tint appears the paper should be removed.
For those papers which it is desirable to keep for some time, as during a journey, it is recommended that into one vessel of porcelain you put about five or six milliliters of the strong aceto-nitrate above described, and into another some distilled water; you plunge completely both sides of the waxed and iodized paper in the first fluid, and allow it to remain about four or five minutes; withdraw it, and plunge it immediately into the bath of distilled water, in which let it soak for not less than four minutes. When these papers are carefully dried they may be preserved for some time for use, and by lessening the dose of nitrate of silver this period may be considerably prolonged. It will of course be understood by all who have followed the processes described up to this point, that the papers which are prepared for keeping are not those which are the most sensitive; hence it is necessary to expose such a much longer time in the camera than those prepared by the stronger solution of silver. The more sensitive variety, under ordinary circumstances of light, will require an exposure in the camera of about 20 seconds, the less sensitive demanding about 10 or 15 minutes, according to the circumstances of light.
The picture is developed by the aid of gallic acid dissolved in distilled water. Le Gray finds the following to be the best proportions:-
Distilled water.....40 fluid ozs.
Gallic acid 60 grains.
The paper is to be plunged into this solution, and allowed to remain until it is fully developed. The time will vary from ten minutes to two hours or more, according to the intensity of the rays incident on the paper when in the camera. The development of the image is much accelerated by the addition of 15 or 20 drops of the aceto-nitrate of silver.
It is found convenient often, when on a journey, to give a temporary fixedness to the pictures obtained, and to complete the process with the hyposulphite at any time on your return home. A wash of 360 grains of bromide of potassium to two quarts of water is the strength which should be employed. The process of fixing with hyposulphite consists, as in other preparations, simply in soaking the paper until the yellow tint of the iodide has disappeared; the details are particularly given in the chapter on Fixing Photographs.