Marvin:
It has been a good discussion even if we cannot agree on everything.
As to who used what, when and how. Our understanding of materials and processes of Ye Olden Times is so fragmented as to be almost completely useless. Some say they did use varnish, some say they may have, others say they didn't. Certainly chemical analysis does not detect much of it - though they are only sampling a very minute amount of the surface areas. Don;t even get me started about black oil!
Either way, it's nice to have a discussion about it. You are clearly a very skilled painter and you have a process that works great for you - it shows believe me. Your points are well taken - certainly we must be informed and take proper precautions.
As Virgil says, check back with me in 100 years - likely I will have changed my mind on some of these positions I take today.
