Bill from British Columbia sent in an e-mail asking how to remove silicone caulking from his acrylic shower floor. For many years we had nothing that would remove silicone caulking from a bathtub. Then all the companies came out with silicone caulking removers. Then they all disappeared (or will disappear soon) because, although they worked well on ceramic tiles, they did damage to acrylic tubs and walls.
Update 2008: "Re-Mov" - Silicone & Adhesive Remover has come out on the market. This is a type of solvent that will dissolve a lot of adhesives and although it does not dissolve Silicone, it does successfully break the bond between the silicon and the substrate. What is great is that it is safe for both fiberglass and vinyl - and most rugs! It will even clean up Polyurethane Adhesives! I've tried it. It works. www.RemovCanada.com
The problem we still have when we want to re-caulk a bathtub is that new silicone caulking will not stick well to old silicone caulking. Hence you must completely remove the old silicone, even the little residue that is left when you cut it off. But all hope is not lost. In talking to the technical department of one of the caulking companies we came up with two solutions to the problem if you do not have the new Re-Mov chemical product to get a clean surface by simply wiping.
Start by cutting off as much of the old silicone caulking as you can. Then make a thick paste with ordinary flour and water. Don't use whole wheat flower, we need the good old fashioned sticky stuff. Take this dough-like putty and rub it over the bit of silicone that is still forming a film on the tile or tub. This dough will roll the silicone up into itself and then you can rinse off the dough -- leaving a clean surface ready for new caulking.
Even more reliable is to use crepe as an eraser. You can actually purchase crepe blocks designed for cleaning sandpaper from such woodworking stores as LeeValley.com or you can simply use old crepe shoe soles. The silicone tends to roll up under the crepe, leaving the surface well 'erased' and ready for fresh caulking.
If you are cutting away caulking often, the Oscilating power tool does this efficiently with the flexible scraper blade.