
Tayler O. answered 07/17/19
Traditionally and Digitally trained Visual Development Artist
Hi James!
This is a really interesting question especially considering artists of the past. From my knowledge it is best to let a painting completely dry before varnishing it. Personally, in the past I have varnished paintings and run across the issue of it catching dust and particulates from the area it was in.
At the college I went to they had specific wood "shelves" that would hold your paintings and keep them protected from people scuffing them or having them collect dust.
Some of the plein air painters in my region will actually have their paintings hung up while they are still wet (especially during competitions). Some of the frames nowadays are able to accommodate wet paint while still retaining the brushstrokes and design of the overall piece.
Hope this was helpful in one way or another! :)