"We first washed the paper with a solution of nitrate of silver, fifteen grains to the ounce, going over the surface in all directions with a camel-hair brush. As soon as the fluid ceased to run, the paper was rapidly dried before the fire, and then immersed in a solution of iodide of potassium, 500 grains to the pint of water. We used to draw it through the solution frequently by the corners, and then let it lie till the yellow tint was visible at the back. It was then immediately taken to the pump and pumped upon vigorously for two or three minutes, holding it at such an angle that the water flushed softly over the surface. We then gave it a few minutes in a rain-water bath, inclining the dish at different angles to give motion to the water. By this time the iodide of silver looked like pure solid brimstone in the wet paper. Then we knew that it was good, and hung it up to dry.
"To make this paper sensitive, we took 5 drops of gallic acid (saturated solution), 5 drops of glacial acetic acid, 10 drops of a 50-grain solution of nitrate of silver, and 100 drops of water. The sensitive wash was poured upon a glass plate, and the paper placed thereon. We used to lift the paper frequently by one or other corner till it was perfectly limp. We then blotted off and placed in the camera, where it would keep a good many hours.
"Whether such pictures would have come out spontaneously under the developing solution, I know not, for we had not patience enough to try. We forced them out in double quick time with red-hot pokers; and great was the alarm of my wife to see me rush madly about the house armed with these weapons. Yet the plan had its advantages; by presenting the point of the poker at a refractory spot, its reluctance to appear was speedily overcome, and we persuaded out the shadows.
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"P.S.—I now have the first picture I ever did, little, if at all, altered. It was done in July, 1845, with a common meniscus lens. I have just got a capital negative by Dr. Diamond's plan, but which is spoiled by the metallic abominations in Turner's paper."
A Collodion Difficulty.—With reference to Mr. J. Cook's collodion, I would suggest that his ether was indeed "still very strong" of acid; by which the iodine was set free, and gave him "nearly a port-wine colour." This is a common occurrence when the ether or the collodion is acid. The remedy is at hand, however. Powder a few grains of cyanide of potassium, and introduce about a grain at a time, according to the quantity: shake up till dissolved, and so on, until you get the clear golden tint. Thus will "the mystery be cleared up." I need not say that the essential properties of the solution will not be impaired.
Andrew Steinmetz.
P.S.—In a day or two I shall send you a recipe for easily turning to immediate use the "used-up dipping baths" of nitrate, without the troublesome process recommended to one of your correspondents.
Ferricyanide of Potassium.—I have used with success the ferricyanide of potassium (the red prussiate of potash, as it is called) for removing the stains contracted in photographing. This it does very readily when the stains are recent, and it has no injurious effect upon cuts and sore places should any exist on the hands. An old stain may with a little pumice be very readily removed. I have mentioned this to several friends, and, if not a novelty, it is certainly not generally known.
S. Pelham Dale.