Tom is correct in my opinion. In toning with metals such as gold, palladium and platinum there is considerable evidence that the precious metals actually plate, or perhaps even replace the silver. I was involved in a rather long thread about this several months ago on a couple of other threads and during the course of the exchange of information did some testing of kallitype prints toned in palladium and platinum. The tests involved bleaching the toned kallitype prints in a strong solution of Kodak R-14. If you bleach an untoned silver print the image will bleach away to virtually nothing, but a print toned with palladium or platinum will retain up to 95% of its original density. I did not bleach any of my gold-toned kallitypes but I suspect that a well-toned gold print would fare just as well because the chemical mechanism of toning is thought to be the same as for palladium and platinum.
Originally Posted by Tom Stanworth
BTW, in my experience with toning kallitype prints, using both gold, palladium and platinum, the end result of toning is to give slightly more contrast by opening up the highlights a bit and adding density in the shadows.
Anyone seriously interested in toning silver gelatin prints should consider obtaining a copy of Tim Rudman’s The Photographer’s Toning Book. It has extensive information and also many beautiful examples of toning.