That is curious. I have never noticed that it takes longer to tone heavier papers than thin ones, and I have toned very thin vellums and papers up 140lbs. With the toner I use the toning is visually complete in about 2-3 minutes.
However, you need to bear in mind that visual appearance is no indicator of how high a percentage of the silver metal has been replaced with the platinum or palladium. I reported some months ago some tests that were done for me by the Getty which showed that replacement was still taking place at twenty minutes, even though most of it was over by about ten minutes. This of course begs the question, how much is good enough for archival quality similar to regular Pt./Pd?
Originally Posted by buggy