I have started experimenting with rolling on Timeless and Rosco Clear Coat varnishes on 100% cotton canvas (Canson Infinity Museum ProCanvas Matte) and 100% Cotton paper (Canon Fine Art Enhanced Velvet). Both substrates seem to shrink after I coat them. Is that normal? Assuming you have a fixed frame size in mind do most people just guestimate and print them a little larger trim as appropriate after mounting? If I switch to an HVLP sprayer would shrinkage still be a problem?
Cotton is just like paper in that if it absorbs too much water it will shrink, and not necessarily in a uniform manner. The 70/30 polyester/cotton isn't too bad, but the 100% cotton is very easy to shrink if you put too much varnish on. The best way to apply roll on varnish is to put three
very light coats on letting each coat dry before applying the next. Having used Timeless I prefer Eco Print Shield as I found Timeless dried so fast that it left roller marks.
If for some reason you're still having problems you can make the canvas partially waterproof by first spraying a light coating of spray-on solvent varnish like Moab or Hahnemuhle which will block most of the water from being absorbed.
