I have a Group of Seven original in my shop which was framed in 1955. The customer would like to have me remove the kraft paper dust cover (believed to be glued down) without any rips if possible (on the previous one I encountered some small tears after patiently removing with a razor blade between the frame and the cover using a very small 'fileting' cut). Reason to keep is the information and artist signature on the back ( to be kept in an envelope on the back of the new Lineco dust cover). Any suggestions? Steam? thanks in advance. P.S. Framing job is only 2% of art purchase price, I don't have a geologist's degree.