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178 THE PHOTOGRAPHIC NEWS. [APRIL 9, 1880. complete control over the density and detail of the finished negative; there are, however, certain disadvantages con nected with this mode of developing as usually practised, owing chiefly to the rapid deterioration of the developing solutions when mixed ready for use. It is well known that an acid solution of pyrogallic will keep and retain its properties for a very long time; but when an alkali is used in place of the acid, in a few minutes the mixture becomes decomposed and utterly useless. Even a solution of plain pyrogallic in water will only keep a very short time, and begins to deterio rate from the moment it is mixed. For these reasons it has, I believe, now become the general custom to make the deve loping solution by adding a small quantity of dry pyrogallic acid to the quantity of water required for the development of each separate plate, which is better than the old plan of using dropping bottles or tubes ; but there are grave ob jections besides the inconvenience of measuring small quan tities of dry pyrogallic ; in the first place, small particles of this light feathery substance are very apt to blow about the dark room, and would in time doubtless accumulate in odd corners and cause trouble in various ways; secondly, and more important, it is practically impossible to guess the exact quantity required for each plate so as to keep the developer at a uniform standard strength ; consequently, as the density of the negative depends to a great extent upon the quantity of pyrogallic in proportion to the other ingre dients, it becomes exceedingly difficult to obtain negatives of anything like uniform printing density. To obviate this difficulty it has been proposed—first, I think, by Mr. Swan—to make separate standard solutions of ammonia and bromide and pyrogallic in water of the strength required for use, and to mix equal parts of these two solutions just before developing the plate. This plan I think far preferable to the others I have mentioned, if we can only keep the solutions always in their best condi tion, and always ready for use. Both these conditions are fulfilled by the methods I have now to describe, and which I have used for the last six months in daily practice in the studio. Make two stock solutions, and label them No. 1 and No. 2. No. 1. Pyrogallic acid ... ... ... 1 ounce Glycerine 1 „ Methylated alcohol 6 ounces Mix the glycerine and spirit, and add to the pyro. No. 2. Bromide of potassium (or ammonium) 60 grains Liquor ammonia *880 1 ounce Glycerine ... 1 ounce Water 6 ounces The above stock solutions will keep any length of time. To make the developer, add one part of No. 1 to fifteen parts of water, and label this bottle D (developer); in another bottle mix one ounce of No. 2 with fifteen ounces of water, and label A (accelerator). It will be found convenient, to avoid mistakes in the imperfect light of the dark room, to have these two bottles of different shapes. Either of the above solutions will keep two or three days. When required for use, pour into a clean glass measure equal parts of D and A, adding the A last just before using. Place the dry exposed plate face up in a shallow dish or tray, and pour the mixture steadily over the plate, avoiding air-bubbles ; should any adhere to the surface of the plate, at once remove them with the finger or a camel’s-hair brush kept for the purpose; rock the dish gently, taking care to keep the plate well covered with the solution ; in a few seconds the image will appear, and if the exposure has been well timed, all the details will be out, and the development complete in about one minute, when the negative should be well washed under the tap and placed at once in the fixing bath. Do not hurry the development, but allow the plate to remain in the solution after all the details are visible, until the required density is obtained. With this developer used in the above proportions, there is no danger of fog, except from the action of light. If, on the application of the mixed developer, the image flashes out, and the details in the shadows appear too quickly, it will indicate that the plate has been over exposed, therefore at once throw off the mixed developer, and, without stopping to wash the plate, flood it with D aione, when the development will be checked, and will proceed more slowly, while the image gains in density; if too slowly, or the negative appears to be getting too intense, add a very little A. There will, however, usually be sufficient of the latter left on the plate to complete the development with the simple addition of a sufficient quantity of solution D. A very little experience will enable the operator to produce a good printing negative from a plate which, if developed with the full proportion of A, would have been utterly useless from over-exposure. (In very warm, bright weather, it will, perhaps, be found an advantage to use rather more D than L in the mixed developer, giving just sufficient exposure to avoid hard ness in the negative.) Under-exposure can be cor rected to a great extent by increasing the proportions of A in the mixed developer, but the addition should be made at once, before the development has proceeded too far, or the effect will be to increase the density and cause too much contrast in the negative. The proportions of the mixed developer can be varied at will by the operator according to the character of the results he wishes to produce. The proportions given above are suited to my own plates, and some others I have tried, but probably would not suit all kinds of plates without some modification of the stock solution, such as the addi tion of a greater quantity of the restraining bromide in the No. 2 solution. These concentrated stock solutions will be found very convenient to use, and a great saving of time in weighing and measuring small quantities. With regard to the keeping properties of the No l.pyro solution, I have found no difliculty whatever ; the glyce rine seems to act as a perfect preservative. The bottle marked No. 1, which I now hand round for your inspection, was mixed last August, more than six months ago; the solution seems to have undergone no change ; it is now about the same colour as the day it was mixed. That this is owing to the glycerine, and not to the alcohol, is proved by the other bottle marked No. 2, which contains no alcohol, but the same proportions of pyro and glycecrine mixed with water and kept six months; this, you will observe, has become slightly discoloured, but is still in good con dition. I am satisfied of the value of glycerine (or glycerine and spirit) as a solvent and preservative of pyrogallic acid, and I have also every reason to believe that the presence of a small portion of glycerine in the developer is of great benefit; it seems to act as a restrainer, and entirely pre vents fog even with a very small proportion of free bromide; in fact, with some plates I have found no difficulty in dis pensing with the bromide altogether. I also find, when using this developer, that I have far greater control over the density of the finished negative, as the developer never fogs. It is only necessary to allow it to remain on the plate until the required density is obtained, thus obviating the necessity for after-intensification. Since adopting this method I have bad no occasion to intensify any of my negatives. I have brought with me two or three negatives for your inspection ; they have all received different exposures, two on each plate, and, although developed with the glycerine developer in the usual way without special care, you will find that in every instnace the densest negative is that which has received the longest exposure. This effect may