Silicone can be removed by scraping with a blade or craft knife, but that can be laborious and isn't always practical. Instead, try using a solvent that's made to remove silicone.

There are a number of solvents on the market, but one of the best is Silicone-Be-Gone, a product made by DAP and developed specifically for removing silicone. Can be found at many home building centers or hardware stores. It can be used both for dissolving cured silicone and for cleaning up the area around freshly applied silicone. The product takes several hours to work completely.

It's also an oil-based solvent that has a noticeable odor, so use with proper ventilation. It's also a good idea to wear gloves to minimize contact with your skin. Follow manufacturer's instructions.

If you don't want to use the stronger commercial products, you can remove silicone with mineral spirits or rubbing alcohol. These products are safer, but they will take longer to work, and they will likely also require some elbow grease and a fair amount of scraping.