The gelatine prints should be toned at once after printing. Even if they are kept in a perfectly dark place, the half tones and high lights quickly discolor.
The separate toning baths are easily prepared. What is called the stock solution is made as follows: 15 grs. chloride gold and sodium, 7½ oz. of water.
Dissolve and keep in a tightly corked bottle, marked "Gold Solution." Chloride of gold and sodium comes already prepared in 15 grain-quantities, and costs thirty cents a bottle.
The other stock solution is a saturated solution of bicarbonate of soda. A saturated solution is a solution which contains a little more of the substance dissolved in it than it can hold in solution. This is shown by a deposit on the bottom of the bottle.
To make the toning bath, take 3½ oz. of water in the graduating glass and add ½ oz. of the gold solution. Dip a piece of blue litmus paper into the solution, and if it does not turn the paper red add a little more of the gold solution until it does. Then add enough of the bicarbonate of soda solution till it turns the litmus paper back to blue. A few drops of the soda solution should be added at a time, stirring the solution with a glass rod.
Mix the bath half an hour before wanted for use. Place the prints in this bath without previous washing, and tone till the required color is obtained. Rinse and place in a fixing bath composed of 1 oz. of hyposulphite of soda and 8 oz. of water. Leave them in this fixing bath five minutes, then wash for half an hour in running water.
In preparing stock solutions, label the bottles and write the formula with direction for use on the label. This saves time and trouble.
In preparing chemical solutions one must be very exact, as a little more or less of one ingredient sometimes produces chemical changes in the solution, rendering it useless for the purpose for which it was intended.
Pauline asks how to fume paper. Fuming albumen paper makes it easier to print and tone. Freshly sensitized paper does not need fuming, but paper that has been prepared some time should be fumed before using. To do this pin the paper inside a box, a wooden soap-box is just the thing, and set it over a saucer of ammonia water. Cover the box with a blanket, and let it remain for fifteen minutes. Use at once.