I add this dissolved iodide of silver to the preceding mixture, and shake it up: there remains, as a sediment at the bottom of the bottle, a considerable thickness of all the above salts, which serve to saturate the alcohol by which I replace successively the saturated which I have extracted by degrees in the proportions below.
3rd. Having these two bottles ready, when I wish to prepare negatives, I take about 200 grammes of the solution No. 1. of céroléine and alcohol, with which I mix 20 grammes of the solution No. 2.; I filter the mixture with care, to avoid the crystals which are not dissolved, which always soil the paper; and in a porcelain tray I make a bath, into which I lay to soak for
about a quarter of an hour the papers selected and cut, five or six at a time, till the liquor is exhausted. Taken out, hung up by the corner, and dried, these papers, which have taken a uniform rosy tint, are shut up free from dust, and kept dry. With regard to the sensitizing by nitrate of silver, the bringing out of the image under the action of gallic acid, and fixing the proof by hyposulphite of soda, I follow the usual methods, most frequently that of Mr. Le Gray.
I add only, if I have any dissolved, 1 or 2 grammes of camphorated spirits to 1 litre of the solution of gallic acid.
Allow me, Sir, to say a few words on the great advantages I have always remarked in preparing my negatives by this method.
All those who use papers waxed by Mr. Le Gray's process, know how many, how tedious, and how difficult are the operations before the sensitizing by nitrate of silver. They know too how much care is necessary to obtain papers uniformly prepared and without spots, in the midst of such long operations, in which there are so many opportunities for accidents. In fact, one must be always upon one's guard against the impurities of the wax obtained from the shop; against the dust during the impregnation of the paper; and, while using the iron, against the over-heating of the latter, and against the bad quality of the paper used to blot.
Photographers know also how much wax they lose by this process, and how much it costs for the quantities of paper necessary to dry it properly. They know likewise how difficult and tedious it is to soak a waxed paper which has been previously in a watery solution. On the contrary, by the method I have described, the iodizing and the waxing is done by one single, simple, and rapid process; the saturation is, as may be conceived, very uniform, and very complete, thanks to the power of penetration possessed by the alcohol; and that marbled appearance of the ordinary waxed proofs, which is so annoying, cannot be produced by this method, thanks to the character of the céroléine: this body is, in fact, of a remarkable elasticity.
The solution of céroléine in the alcohol is more easy to prepare, and comparatively costs little; and the remains of stearine and of myricine can either be sold again, or, in any case, may be used to wax fixed proofs.
The solution of which I have given you the formula, is photogenic to a very high degree; in fact, used with papers, either thin or stout, it gives, after the first bath of gallic acid, blacks of an intensity truly remarkable; which it is impossible to obtain to the same degree with Le Gray's paper, and which other papers scarcely take after having been done a second time with the acetic acid, or the bichloride of mercury. At the same time, it preserves the lights and the half-tones in a way that surprises me upon each new trial (I have not yet been able to obtain one clear proof by gallic acid, with the addition of nitrate of silver). The transparency of the proofs is always admirable, and the clearness of the object yields in nothing to that of the proofs obtained by albumen.
The paper, prepared in the manner I have described, is also very quick as compared with Le Gray's paper—at least one fourth quicker; and preserves its perfect sensitiveness in the same proportion of time, three days in twelve. Thus, it is at the same time quicker and less variable. This comparative rapidity may be very well understood, by remembering that the céroléine is an element much softer than its compound; and possesses a photogenic aptness which is peculiar to itself, which science will, no doubt, soon explain.