PHOTOGRAPHIC CORRESPONDENCE.
Processes upon Paper.—The favourable manner in which the account I have given of the Collodion process has been received, not only by your readers in general, as has been evinced by many private letters, but also by the numerous correspondents it has drawn forth, induces me, after some little delay, to request space for a description of the following processes upon paper. In giving these I wish it to be understood that I may offer but little that is original, my object being to describe, as plainly as I possibly can, these easy methods, and to make no observation but what I have found to be successful in my own hands. I have had the good fortune to obtain the friendship of some of the most successful photographers of the day; and taking three very eminent ones, I find they have each some peculiarities in his mode of manipulation, varying with each other in the strength of the solutions employed, and producing results the most agreeable to their respective tastes. Reviewing these different processes in my own mind, and trying with patience the various results, I conclude that the following quantities are calculated to produce an adequate degree of sensibility in the paper, and yet to allow it to be prepared for the action of light for many hours previous to its use, and yet with more certainty than any other I am acquainted with. I think I may always depend upon it for twenty-four to thirty-six hours after excitement, and I have seen good pictures produced upon the third day. I believe it is a rule which admits of no contradiction, that the more you dilute your solution, the longer the excited paper will keep; but in proportion to its diminished sensibility, the time of exposure must be prolonged, and therefore I am, from this waste of time and other reasons, disposed to place much less value upon the wax-paper process than many do.
The process I am about to describe is so simple, and I hope to make it so intelligible to your non-photographic readers, that a perfect novice, using ordinary care, must meet with success; but should I fail doing so upon all points, any information sought through the medium of "N. & Q." shall meet with explanation from myself, if not from other of your experienced correspondents, whose indulgence I must beg should the communication be deemed too elementary, it being my earnest desire to point out to archæologists who are desirous of acquiring this knowledge, how easily they themselves may practise this beautiful art, and possess those objects they would desire to preserve, in a far more truthful state than could be otherwise accomplished.
I have not myself met that uniform success with any other paper that I have with Turner's photographic of Chafford Mills: a sheet of this divided into two portions forms at the same time a useful and also a very easily-managed size, one adapted for most cameras, forming a picture of nine inches by seven, which is adequate for nearly every purpose. Each sheet being marked in its opposite corners with a plain pencil-mark on its smooth side (vide antè, p. 372.), the surface for
all future operations is in all lights easily discerned. In my instructions for printing from collodion negatives, a form of iodized paper was given, which, although very good, is not, I think, equal to the following, which is more easily and quickly prepared, exhibits a saving of the iodide of potassium, and is upon the whole a neater mode.
Take sixty grains of nitrate of silver and sixty grains of iodide of potassium; dissolve each separately in an ounce of distilled water; mix together and stir with a glass rod. The precipitate settling, the fluid is to be poured away; then add distilled water to the precipitate up to four ounces, and add to it 650 grains of iodide of potassium, which should re-dissolve the precipitated iodide of silver, and form a perfectly clear solution; but if not, a little more must be carefully added, for this salt varies much, and I have found it to require 720 grains to accomplish the desired object.
The fluid being put into a porcelain or glass dish, the paper should be laid down upon its surface and immediately removed, and being laid upon a piece of blotting-paper with the wet surface uppermost, a glass rod then passed over it to and fro ensures the total expulsion of all particles of air, which will frequently remain when the mere dipping is resorted to. When dry, this paper should be soaked in common water for three hours, changing the water twice or thrice, so as to remove all the soluble salts. It should then be pinned up to dry, and, when so, kept in a folio for use. I have in this manner prepared from sixty to eighty sheets in an evening with the greatest ease. It keeps good for an indefinite time, and, as all experienced photographers are aware, unless you possess good iodized paper, which should be of a primrose colour, you cannot meet with success in your after-operations. Iodized paper becomes sometimes of a bright brimstone colour when first made; it is then very apt to brown in its use, but tones down and improves by a little keeping.
To excite this paper, dissolve thirty grains of nitrate of silver in one ounce of distilled water, and add a drachm and a half of glacial acetic acid; of this solution take one drachm, and one drachm of saturated solution of gallic acid, and add to it two ounces and a half of distilled water. The iodized surface of the paper may then be either floated on the surface of the aceto-nitrate of silver or exciting fluid, and afterwards a rod passed over, as was formerly done in the iodizing, or the aceto-nitrate may be applied evenly with a brush; but in either instance the surface should be immediately blotted off; and the same blotting-paper never used a second time for this, although it may be kept to develop on and for other purposes. It will be scarcely needful to observe that this process of exciting must be performed by the light of a candle or feeble yellow light, as must the subsequent development. The excited paper may be now placed for use between sheets of blotting-paper; it seems to act equally well either when damp or when kept for many hours, and I have found it good for more than a week.
The time for exposure must entirely depend upon the degree of light. In two minutes and a half a good picture may be produced; but if left exposed for twenty minutes or more, little harm will arise; the paper does not solarize, but upon the degree of image visible upon the paper depends the means of developing. When long exposed, a saturated solution of gallic acid only applied to the exposed surfaces will be sufficient; but if there is little appearance of an image, then a free undiluted solution of aceto-nitrate may be used, in conjunction with the gallic acid, the former never being in proportion more than one-third. If that quantity is exceeded, either a brownish or an unpleasant reddish tint is often obtained. These negatives should be fixed by immersing them in a solution of hyposulphite of soda, which may be of the strength of one ounce of salt to eight ounces of water—the sufficiency of immersion being known by the disappearance of the yellow colour, and when they have been once immersed they may be taken to the daylight to ascertain this. The hyposulphite must now be perfectly removed by soaking in water, which may extend to several hours; but this may be always ascertained by the tongue, for, if tasteless, it has been accomplished. If it is deemed advisable—which I think is only required in very dark over-done pictures—to wax the negative, it is easily managed by holding a piece of white wax or candle in front of a clean iron rather hot, and passing it frequently over the surface. The superabundant wax being again removed by passing it between some clean pieces of blotting-paper. Although the minuter details can never be acquired by this mode which are obtained by the collodion process, it has the advantage of extreme simplicity, and by the operator providing himself with a bag or square of yellow calico, which he can loosely peg down to the ground when no other shade is near, to contain spare prepared papers, he can at any future time obtain a sufficient number of views, which afterwards he can develop at his leisure.