3150. Silver Bath

3150. Silver Bath. Make a solution in the proportion of GO grains nitrate of silver to 1 ounce water. Test the solution with litmus paper, and if slightly alkaline, or neutral, add nitric acid to produce a faint red reaction to the paper. The best method is to add a few drops of chemically pure nitric acid to an ounce of water, and add this solution to the silver bath a very few drops at a time. Then coat a plate with collodion and let it remain in the bath all night. The freshly made collodion can be used for this purpose, and thus both collodion and silver solution or bath be made ready for work at the same time.

3151. Developing Solution

3151.      Developing Solution. This may be made in stock solution of the simple sulphate of iron and water, and then reduced in strength and made ready for use each day. For the stock solution take water, 16 ounces; sulphate of iron, 4 ounces. Dissolve and filter. "When wanted for use, take stock solution, 1 ounce; water, 4 ounces; acetic acid (No. 8), 1/2 ounce. The addition of about 1/2 ounce alcohol to the above formula often facilitates the smooth flowing of the solution on the plate. It is particularly essential when the bath has been in long use and is "saturated" with ether and alcohol from the plates.

3152. Re-developing Solution

3152.      Re-developing Solution, for adding vigor and intensity to the negative, is made of water, 1 ounce; pyrogallic acid, 1 grain; citric acid, 1 grain. Pour into a small beaker or cupping glass about 1 ounce of this solution, and add, by means of a pipette, 5 or 6 drops of a solution of 20 grains nitrate of silver dissolved in 1 ounce water. Immediately flow this solution over the plate, occasionally returning the solution to the little beaker glass. As soon as the solution begins to assume a wine color, it is acting with vigor on the negative and should be closely watched, that the negative does not become too intense. When sufficiently dense, throw away the solution and thoroughly wash both the negative and the glass. The latter should always bo kept perfectly clean and free from any deposit from the re-developing solutions.

3153. Negative Varnish

3153.    Negative Varnish of excellent quality can always be secured at the dealers in photographic materials. In an emergency common shellac varnish, somewhat thinned down with alcohol, and filtered through cotton, will answer the purpose. (See No. 2935 (French Transparent Colorless Varnish).)

3154. The Causes of Failure

3154.     The Causes of Failure would almost require a chapter by themselves; a long experience convinces us that nine out of every ten failures occur from a want of care, the presence of dirt, negligence. One cannot be over-nice, careful or cleanly - the best results always rewarding the most painstaking.

3155. To Enamel Cameo Pictures

3155.     To Enamel Cameo Pictures. Ordinary well polished glass plates are coated with normal collodion of the usual description, and when the film has set perfectly, but has not become completely dry, the pictures, which have previously been trimmed and finished, are dipped rapidly into alcohol, and applied without delay to the plates. The prints are pressed and rubbed down with smooth writing paper, and the operation of mounting is proceeded with as soon as the backs of the pictures have become white; or, in other words, as soon as the alcohol has again evaporated. The cardboard should be allowed to remain in water for at least half an hour previously to its being employed for mounting. The more rapidly the pictures are applied and pressed upon the collodion surface, the more beautiful will be the finished result.