7. The plate having been taken from the camera, and placed upon a levelled stand, or held in the hand, develop immediately the latent image with the following solution:—
Iron developing solution.—Protosulphate of iron, 1⁄4 oz.; glacial acetic acid, 1⁄4 oz.; spirits of wine, 1⁄2 oz.; distilled water, 8 ozs.: mix. Pour on of this solution only enough to cover the plate easily, commencing at that edge of the negative which stood uppermost in the camera; move the solution to and fro until it has become intimately mixed with the silver on the plate; then pour off into the developing glass, and at once return it on to the plate. When as much intensity has been obtained as possible with the iron developer, it should be thoroughly removed by washing with water. Any intensity may be obtained afterwards by using either of the following solutions:—
8. Intensifying solution.—Pyrogallic acid, 6 grs.; glacial acetic acid, 1⁄4 oz.; distilled water, 6 ozs.: mix. A few drops of a 30-gr. solution of nitrate of silver, the quantity to be regulated according to the intensity required, to be added, at the moment of using, to as much of the pyrogallic solution as may be necessary.
Intensifying solution (another form).—1. Pyrogallic acid, 8 grs.; citric acid, 20 grs.; distilled water, 2 ozs. 2. Nitrate of silver, 8 grs.; distilled water, 2 ozs. Mix small quantities of the solutions 1 and 2, in equal portions, the moment before using.
The pyrogallic solution, made with good acetic acid, may be kept for a month or more in a cool place. Nevertheless, if the conditions of light and situation are unfavourable, I should prefer this solution just made. The iron solutions act best when freshly prepared.
It is supposed by some that a prolonged action of the iron developer produces fogginess. This may be the case when impure or improperly prepared collodion is used, but certainly not when the preparation is pure and of the proper quality.
When the image is sufficiently intense, wash freely with common filtered water; then pour on a saturated solution of hyposulphate of soda, which should immediately remove the iodide of silver: wash again well with water; allow as much as the plate will hold to soak in for at least a quarter of an hour, changing the water occasionally, to remove all traces of hyposulphate; lastly, wash the plate with a little distilled water, stand up to dry, and, if required, varnish either with spirit or amber varnish.
The following solution is also very commonly used for fixing the negative:—Cyanide of potassium, 1⁄4 oz.; water, 12 ozs.
Attention to the following rules and cautions will assist the operator in the production of perfect pictures:—