Acetone, which is a colorless, flammable solvent, can be used to remove silicone caulk. Acetone is available in pure form and is also a common ingredient in paint thinner and fingernail polish remover. It is safe to use on most surfaces; however, it will damage finished wood.
After the majority of the silicone caulk is removed with a utility knife and a razor blade scraper, apply acetone with an abrasive scrubber and scrub away any remaining caulk. Wipe the surface clean with isopropyl alcohol and allow the area to dry thoroughly before applying new caulk. When working with acetone, make sure the room has adequate ventilation.