This section is from the book "Modern Photography In Theory And Practice", by By Henry G. Abbott. Also available from Amazon: Modern photography in theory and practice: A hand book for the amateur.
In toning in the gold bath, it is important to watch several points. One is to see that the high lights and shadows are both toning equally. It is a good plan to look through the print by transmitted light and if you find the same tone as appears on the surface, you are toning down in the emulsion and your tones will hold in the hypo bath; but if the print looks purple on the face and when you look through it, the shadows look red, you can depend upon it you are getting a surface tone and when the print goes into the hypo the surface tone will cut off and you will have the tone you are looking through. The reason is, you have not washed all the free silver off your print. Your gold is depositing in this free silver and when the print goes in the hypo bath, the free silver cuts off and takes your tone with it. By the use of salt in your gold bath, you avoid
The salt also restrains the high lights from over-toning and enables the shadows to tone up at the same time. The salt also saves the fine detail in white drapery. Should you find, in toning, your whites are bleaching, it is because your bath is not alkaline enough, so add a few drops of alkali. On the other hand, if your prints re-fuse to clear up and tone out dead and flat, it is because your bath is too alkaline, in which case add a little acid gold or a drop of citric acid. Intoning Aristo Platinopaper, if you do not have your gold bath alkaline enough, you will get pink whites in the platinum bath. Always remember that pink whites mean that your gold bath was not alkaline enough.
It is impossible to give the exact amount of alkali to use. Almost all waters are alkaline. The litmus paper test must guide you in this. Study and test the water you work with and you will not have any trouble making nice prints. All gold baths should be made up from one to two hours before use and a good plan is to make up a fresh bath for next time, after you get through toning, only adding about a grain of gold and then when ready to tone, adding the gold to tone with. A ripened bath will work much smoother than a fresh one. Many printers like to use one-half old and one-half new bath. Acetate of soda will not have any effect on a toning bath, unless added one hour before use. Acetate of soda will always keep your tone rich and brilliant. In making up a gold bath, remember that neutralizing with sal soda gives warm tones, borax gives brown tones, and bi carbonate soda gives purple tones. Borax is generally used because it is the weakest alkali and a few drops more or less will not get one into trouble as quickly as the stronger sodas do. In some waters it is best to use sal soda as an alkali for the gold bath, as borax may give muddy shadows. If borax is found to give this result, you should try sal soda; but remember that sal soda is a very strong alkali and should be used very cautiously. When the water you use is alkaline it is best to use a very acid gold and acidify your toning bath first. Then add borax or sal soda to bring it up to alkaline. The reason for this is, that the alkali found in the water is a lime alkali and is not the proper kind of alkali to use and will not give you satisfactory tones.