This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
How To Tone. We will now suppose that your Toning Bath has ripened ready for use and the prints are carefully washed, as instructed. Immerse one print in the Toning Bath and with the right hand spray the solution over the print as you watch it toning. You will find that the print will first turn red and gradually the whites will begin to clear and the red will commence to soften down considerably. If the highlights and shadows tone evenly, the bath is working properly. Should the highlights tone chalky, eat away as it were, and the shadows refuse to tone, or change color to any great extent, then the bath is not sufficiently alkaline and a few drops of borax should be added. If the print tones too slowly add a trifle more gold, but before adding the gold it must be neutralized. To do this pour, say two drams of the gold stock solution into a graduate containing two ounces of water. To this add a few drops of your Solution No. 3, the borax, and test with litmus paper. As soon as this gold solution tests alkali, add a dram at a time to the bath until it tones freely. If your bath tones too fast, add more water until your prints tone in from six to eight minutes. A fresh bath will always work more quickly at first than it will after being used a while, so due allowance must be made for this.
62. After you have made these tests and find that the bath is toning properly, you can proceed to tone the balance of the prints. For the beginner, we would advise having no more than 10 or 12 prints in the toning bath at one time. These should be placed in the bath, face down, and moved rapidly from one end of the tray to the other. For those who have had some experience, 15 or 20 prints may be placed in the bath one at a time, and when these prints are partly toned another lot of 15 may be added. When the first lot is finished a third lot should be added, repeating this operation until the entire batch is toned.
63. While the prints are in the toning bath always watch the highlights (by this we mean the whitest part of the print), and if they clear in the time required for the shadows to tone, you will know that the bath is still working properly. Should the highlights tone chalky, after quite a number of prints have been toned - eating away as it were - and the shadows refuse to tone, then you will recognize that the bath has become acid and a few drops of No. 3 Solution (borax) should be added.
64. The first print is apt to tone a little harsh, therefore Solution No. 3 must be added carefully. Better still, add a second print after adding a few drops of No. 3 and see if it does not tone better than the first. Tone these two prints until the highlights or white portions are pure white, allowing the shadows to remain quite warm, almost red, but clear. There must be a reasonable amount of detail in the highlights - they must not be chalky. When your bath tones your test prints to the desired shade in about 6 minutes, the bath is right and ready to receive the balance of prints. Usually a bath will need no altering if it is properly prepared at the start, and an entire batch of prints can be toned without any change in the bath.
65. In order to judge when the highlights are clear place a fresh print in the bath and compare it with those that you are toning. You will notice by the comparison that the fresh print is muddy in the highlights (the whites), while the toned one is clear and crisp. At this stage remove the toned print from the bath to a tray of water and continue to tone the remainder of the prints, watching the action of bath closely. Never have more prints in your Toning Bath than you can handle comfortably so as to insure even toning, and always try to tone all of the prints the same color and depth of tone. Do not have one toned almost blue and another one very warm, but remove them all from the gold bath at exactly the same stage. Remember, after toning a number of prints the acid in the paper is apt to turn the bath to an acid state, and it may be necessary to add a few drops of Solution No. 3 (borax) from time to time, to hold the bath in the proper alkaline condition.
66. The amount of bath recommended in the formula should tone 25 cabinet prints, or their equivalent, without any change or alteration. The temperature of the bath should be 65 to 70 degrees Fahr. A toning bath too cold will cause slow toning. A toning bath too warm will be apt to soften the surface of the prints and also cause surface toning. The toning must be done by weak light, as the paper is more sensitive when wet. When you get the bath to working evenly, judge your tone for the highlights and middle tones, as previously directed. Pay no attention whatever to the deepest shadows; allow them to care for themselves, for when the highlights are round and mellow, the shadows will be rich and velvety. As soon as the halftones are clear remove the prints from the gold bath and place in a tray in which there is plenty of water. If possible place them in running water. After the prints are all toned give them a few changes of fresh water, carefully picking them over and over during the washing. They are then ready for fixing.