PHOTOGRAPHIC CORRESPONDENCE.
Dr. Mansell having forwarded to me for publication the accompanying account of his mode of operation, I have much pleasure in laying it before the readers of "N. & Q.;" because my friend Dr. Mansell is not only so fortunate in his results, but is one of the most careful and correct manipulators in our art. The proportions which he recommends, and his mode of operating, are, it will be seen, somewhat different from those hitherto published. In writing to me he says: "I make a point of making a short note in the evening of the day's experiments, a plan involving very little trouble, but of great service as a reference." If all photographers would adopt this simple plan, how much good would result! Dr. M. complains to me of the constant variation he has found in collodion; (with your permission, I will in your pages furnish him, and all your readers with some plain directions on this point); and he has given me some excellent observations on the "fashionable" waxed-paper process, in which he has not met with such good results as he had anticipated; although with much experience which may some day turn to good account. Dr. Mansell concludes with an observation in which I entirely concur, viz. "That the calotype process is by far the most useful; and I find the pictures it gives have better effect than the wax ones, which always to me appear flat, even when they are not gravelly."
H. W. Diamond.
The Calotype on the Sea-shore.—The great quantity of blue light reflected from the sea renders calotyping in its vicinity much more difficult than in the country; the more distant the object, the greater depth has the blue veil which floats over it, and as a consequence of this disproportion, if time enough is given in the camera to bring out the foreground, the sky becomes red, and the distance obscured. After constant failures with papers iodized in the usual manner, I made a number of experiments to obtain a paper that would stand the camera long enough to satisfy the required conditions, and the result was the following method, which gives an intensity of blacks and half-tones, with a solidity and uniform depth over large portions of sky, greater than I have seen produced by any other process. Since I adopted it, in the autumn of 1852, I have scarcely had a failure, and this success induces me to recommend it to those who, like myself, work in highly actinising localities.
The object of the following plan is to impregnate the paper evenly with a strong body of iodide of silver. I prefer iodizing by the single process, and for this purpose use a strong solution of iodide of silver, as the paper when finished ought to have, as nearly as possible, the colour of pure iodide of silver.
Take 100 grains of nitrate of silver, and 100 grains of iodide of potassium[[4]], dissolve each in two ounces of distilled water, pour the iodide solution into the nitrate of silver, wash the precipitate in three distilled waters, pour off the fluid, and dissolve it in a solution of iodide of potassium, about 680 grains are required, making the whole up to four ounces.
Having cut the paper somewhat larger than the picture, turn up the edges so as to form a dish, and placing it on a board, pour into it the iodide solution abundantly, guiding it equally over the surface with a camel-hair pencil; continue to wave it to and fro for five minutes, then pour off the surplus, which serves over and over again, and after dripping the paper, lay it to dry on a round surface, so that it dries equally fast all over; when almost dry it is well to give it a sight of the fire, to finish off those parts which remain wet longest, but not more than just to surface dry it.
Immerse it in common rain-water, often changing it, and in about twenty minutes all the iodide of potash is removed. To ascertain this, take up some of the last water in a glass, and add to it a few drops of a strong solution of bichloride of mercury in alcohol, the least trace of hydriodate of potash is detected by a precipitate of iodide of mercury. A solution of nitrate of silver is no test whatever unless distilled water is used, as ordinary water almost invariably contains muriates. The sooner the washing is over the better. Pin up the paper to drip, and finish drying before a slow fire, turning it. If hung up to dry by a corner, the parts longest wet are always weaker than those that dry first. When dry pass a nearly cold iron over the back, to smooth it; if well made it has a fine primrose colour, and is perfectly even by transmitted light.
To excite the paper, take distilled water two drachms, drop into it four drops (not minims) of saturated solution of gallic acid, and eight drops (not minims) of the aceto-nitrate solution; mix. Always dilute the gallic acid by dropping it into the water before the aceto-nitrate; gallate of silver is less readily formed, and the paper keeps longer in hot weather. If the temperature is under sixty degrees, use five drops of gallic acid, and ten of aceto-nitrate; if above seventy degrees, use only three drops of gallic acid, and seven of aceto-nitrate. The aceto-nitrate solution consists of nitrate of silver fifty grains, glacial acetic acid two drachms, distilled water one ounce.
Having pinned the paper by two adjacent corners to a deal board, the eighth of an inch smaller on each side than it is, to prevent the solutions getting to the back, lay on the gallo-nitrate abundantly with a soft cotton brush (made by wedging a portion of fine cotton into a cork); and keep the solution from pooling, by using the brush with a very light hand. In about two minutes the paper has imbibed it evenly, and lies dead; blot it up, and allow it to dry in a box, or place it at once in the paper-holder. For fear of stains on the
back, it is better to place on the board a clean sheet of ordinary paper for every picture. It is very important to have the glass, in which the gallo-nitrate is made, chemically clean; every time it is used, it should be washed with strong nitric acid, and then with distilled water.
To develop:—Pin the paper on the board as before; rapidly brush over it a solution of gallo-nitrate, as used to excite. As soon as the picture appears, in about a minute, pour on a saturated solution of gallic acid abundantly, and keep it from pooling with the brush, using it with a very light hand. In about ten minutes the picture is fully developed. If very slow in coming out, a few drops of pure aceto-nitrate brushed over the surface will rapidly bring out the picture; but this is seldom required, and it will sometimes brown the whites. It is better, as soon as the gallic acid has been applied, to put the picture away from the light of the candle in a box or drawer, there to develop quietly, watching its progress every three or four minutes; the surface is to be refreshed by a few light touches of the brush, adding more gallic acid if necessary. Many good negatives are spoiled by over-fidgetting in this part of the process. When the picture is fully out, wash, &c. as usual; the iodide of silver is rapidly removed by a saturated solution of hyposulphite of soda, which acts much less on the weaker blacks than it does if diluted.
If the picture will not develop, from too short exposure in the camera, a solution of pyrogallic acid, as Dr. Diamond recommends, after the gallic acid has done its utmost, greatly increases the strength of the blacks: it slightly reddens the whites, but not in the same ratio that it deepens the blacks.
After the first wash with gallo-nitrate, it is essential to develop these strongly iodized papers with gallic acid only: the half-and-half mixture of aceto-nitrate and gallic acid, which works well with weaker papers, turns these red.
The paper I use is Whatman's 1849. Turner's paper, Chafford Mills, if two or three years old, answers equally well.
M. L. Mansell, A.B. M.D.
Guernsey, Jan. 30, 1854.
Footnote 4:[(return)]
[Having lately prepared this solution according to the formula given by Dr. Diamond (Vol. viii., p. 597.), in which it required 650 grains to dissolve the 60-grain precipitate, we were inclined to think our correspondent had formed a wrong calculation, as the difference appeared so little for a solution more than one-third stronger. We found upon accurately following Dr. Mansell's instructions, that it required 734 grains of iodide of potassium to effect a solution, whilst we have at the same time dissolved the quantity recommended by Dr. Diamond with 598 grains. This little experiment is a useful lesson to our correspondents, exhibiting as it does the constantly varying strength of supposed pure chemicals.—Ed. "N. & Q.">[