I recently took off a back and side splash around the bathroom vanity. Underneath was dried contact cement that had been there approximately 23 years. Sanding did not work. I used a product called "Goo Gone" distributed by Paint Sundry Products Inc. Mississauga, Ont. I applied it with a cotton ball and let it sit a couple of minutes. With rubber gloves on I rubbed it and used coarse steel wool. It does not come off easy. You need a lot of patience and elbow power but it will eventially come off.