The gold for toning is first made into chloride of gold. This chloride of gold is dissolved in water, and then the solution is rendered neutral by adding acetate or bicarbonate of soda.
"Gold is reduced to a metallic state from a neutral or alkaline solution." This toning-bath, therefore, contains a deposit of metallic gold, which is ready to be precipitated by any reducing agent with which it may be brought in contact. Now the action of light on the paper coated with the silver salts has changed the salts into a gold-reducing agent. When the silver print is placed in the gold toning-bath, this sub-salts of silver immediately decomposes the gold salt, and attracts the gold to itself, and it is deposited in a fine powder on the unfixed print, changing the reddish color to brown or black. The unaltered silver chloride on the paper—the portion of the print which has not been exposed to the light—contains no reducing power, so the white portions of the print remain unchanged.
The chemical action of the alkali on the chloride of gold is to separate the chlorine from the gold. The alkali unites with the chlorine, and sets it free from the gold. It forms with the hydrogen in the water a new chemical combination called sodium-trichlor-acetate and hydrochloric acid. The former is harmless to the print, but if there is not enough of the alkali in the solution to neutralize (render harmless) the hydrochloric acid, or, in other words, to liberate and absorb all the chlorine, the chlorine immediately reattacks the silver and stops the action of the gold. The result is a weak flat print. If the prints do not tone, the bath is too acid, and more of the alkali must be added. In order to test a bath to find out whether it is neutral, take a piece of blue litmus-paper and dip it in the bath; if it is acid it will turn the paper red. Add more of the alkali, until enough has been added to turn the paper which has been turned red back to its original blue color. A piece of red litmus-paper when dipped in the toning-bath will turn blue if the bath is too alkaline, but if the bath is neutral the paper will remain red.
Every silver print toned with gold contains four parts of silver to one of gold, the quantity of both being very small. One grain of gold will tone a sheet of paper.
There is a great deal of waste in the silver used in photography, there being thirty-three times as much silver used as remains after the picture is finished.
Silver prints may be toned with platinum, and this method is often used as a substitute for gold toning, the tones obtained being very pleasing in color, and quite as permanent as the gold tones.
Sir Knight John H. Chamberlain, 6 Franklin Avenue, Dayton, O., asks why films are given a glycerine bath, and if the bath can be dispensed with; what will remove the spot of glycerine from a negative caused by the glycerine flowing to the edge and partly drying. Sir John says he is a regular reader of the Camera Club column, and would like to form a Chapter, and asks those of our amateurs who are interested in the plan to please send him their names. The reason for using a glycerine bath is to prevent the film from curling when it is dry. The bath can be dispensed with, but the film rolls up so tightly that it is hard to make it stay flat while placing it in the printing-frame. Use ½ oz. of glycerine to 16 oz. of water, and there will be no trouble with the film being sticky. A little alcohol applied gently with a soft cloth or brush will remove the glycerine from the negative.
Sir Knight James Maynard, Jun., asks if the bottle containing the sensitizing-solution for plain salted paper should be wrapped in non-actinic paper; what camera, lens, plate, and developer Max Miner used for the picture "Sweeping a Sliding-place"; what is the price of Whatman's paper. The sensitizing solution should be wrapped in non-actinic paper, or else kept in a dark place. Max Miner writes as follows in regard to the picture "Sweeping a Sliding-place": "The camera which I used is the Universal, made by the Rochester Optical Co.; the lens is a Morrison R. R., 8½-inch focus, designed for a 6½ by 8½ plate. The camera was a 5 by 7. The plates which I have always used are made by the Blake Dry-plate Co., North Adams, Mass. They are rapid, and always give uniformly good results. I have the best success in developing with pyro, potash, or soda, though I like the eikonogen two-solution developer nearly as well. I never have trouble with pyro stains, as I use an alum bath before fixing. The paper used is lithium, toned and fixed in a separate bath." A large sheet of Whatman's paper may be bought for fifteen cents.
Sir Knight John Mills asks how to make a picture in a pin-hole camera without using plates—if some kind of paper cannot be used. The formula for preparing paper for negatives is too long to be given in the column space devoted to answers to queries. The process will be described later in the columns of the Camera Club. If you have access to a public library, consult a cyclopædia of photography, which will give a formula for making paper negatives. Try a piece of bromade-paper, making an exposure of about fifteen seconds, if in a bright sunshine.
Sir Knight Hubbard Marsh asks what makes the solio prints stick to the glass when they are squeegeed to it for burnishing; a preparation for coating the glass for burnishing; and a good toning-bath. The reason why prints stick to the glass is because the film is soluble, and is apt to soften in warm weather. A very glossy surface can be imparted to prints by washing the glass or ferrotype plate to remove all grease and dirt, then pour on a few drops of a solution made of 1 oz. of benzine and 10 grs. of paraffine. Rub dry with a clean cloth and polish with a piece of chamois or soft cloth. For toning-solution formula see No. 825.
E. H. C. asks if, in photographic contests where no pictures are accepted under 4 by 5, pictures taken on a 4-by-5 plate, and the prints trimmed so as to come a little under this size, would be accepted. Yes, if not trimmed too much.
There is a good story told of the well-known actor Frédéric Lemaitre. One of his weak points was his pride, and he expected the attachés of the theatre in which he played to show as great interest in his performance on the fiftieth night as the audience who were seeing him for the first time. For some time, to his infinite rage and disgust, one of the musicians had been in the habit of taking out a newspaper and perusing its contents during one of his best scenes, when his acting would hold the audience spellbound. He finally forbade this man to read his paper during the performance. The musician refused to submit to the demand, and Lemaitre, when he heard of the refusal, grew mad with rage, and stormed around in great manner. The offender happened to cross the stage while Lemaitre was in his bad humor, and the actor, catching sight of him, cried out, in angry tones:
"You, sir; is it you who has the audacity to read in my great scene, especially when I have forbidden it?"