Laura, thank you for sharing this information. I am sure that many artists will find it very useful and money-saving. In addition to what you suggested, I add a layer between the painting and the plastic bag. Only to prevent the plastic from reacting with the varnish, which I have seen happen before. I use a 1/16" sheet of foam. I buy the roll from ULine and it comes perforated into 12" squares for easy tearing.