Apply a fine mist of denatured alcohol to the caulking bead using the spray bottle. Use your finger to smooth the bead of caulking with your finger before the alcohol evaporates.
Softening Solvents
One item you may have on hand that helps soften silicone is mineral spirits, which is suitable to get silicone off of hard surfaces like tile, marble or concrete. For removing it from plastic or painted surfaces, however, you should use isopropyl alcohol, which won't harm the surface.
WD-40® is very good at removing silicone sealant, but make sure you completely remove it from the surface before applying any new silicone sealant, as they can react.
Windex chemically reacts with silicone forming a film on it where it touches and by spraying a little on your fingers or a tool (keeping it somewhat wet) the silicone won't stick to you or the tool. Allowing you to manipulate it (spread it, push it, etc...) in ways you normally couldn't.
Before you start removing the silicone, make sure your working area and the silicone is dry. This is going to make the process easier and safer. If the area is wet, pat it down with a towel or rag or let it air dry.
Apply a fine mist of denatured alcohol to the caulking bead using the spray bottle. Use your finger to smooth the bead of caulking with your finger before the alcohol evaporates.
As it contains acetic acid, silicone can be softened with white vinegar. This will make it much easier for you to remove it from any surface including glass and tiles.
To smooth silicone caulk, just lay down a nice bead with your caulk gun, then spray a mist of rubbing alcohol on the bead. (The spray head from many different products will fit on the alcohol bottle.) Now, prepare yourself for magical results as you smooth the bead with your finger.
Cured silicone can only be removed mechanically from a surface once cured with either a specialist tool or a sharp blade. Alternatively, soak a cloth with turpentine/paraffin and place over the residue. Put a plastic sheet over the cloth to prevent drying and leave overnight. It should be swollen enough to remove.
Once you have removed most of the silicone, wipe the remnants off using a cloth. You can make the job a bit eaiser by soaking the cloth in methylated spirits. The methylated spirits act as a solvent, breaking down the last of the silicone, making it less sticky and easier to wipe up.
Chisels and Stanley knives are generally common tools for silicone removal.
Once you're removed most of the silicone use a cloth and some methylated spirits to wipe the remnants off. The methylated spirits act as a solvent in this scenario helping break down the last of the silicone and making it easier to manage and less sticky.
Depending on the aplication/finish you require, you can either leave a raised bead or dip a finger in the water and gently run your finger along the bead to push it into the gap and create a smooth hollow in the bead. Remove excess silicone from finger with kitchen roll/cloth prior to continuing.
Smooth the Caulk Bead
Alternatively, you can simply use your finger. Moisten your fingertip in warm soapy water and drag it with light pressure along the length of the bead. If caulking with tape to mask the area around the caulk, remove the tape before the caulk starts to set.
Pot life for the pourable silicones is 45 minutes and they cure overnight at room temperature. Vacuum degassing mixed material using a vacuum pump and chamber to remove entrapped air is recommended.
Can I apply new silicone atop, or alongside old silicone caulk? It is recommended that any old silicone is removed. While new, freshly applied silicone can be applied & will bond to old silicone – the bond isn't as strong as if it were applied to a clean surface.
Baking Soda
Baking soda is another effective method for cleaning silicone. Simply put half a cup of baking soda into a bowl of hot water and let it sit for 10 minutes before rinsing the item with cold water. This process will help remove any residue left by oils, grease, and grime.
Scrape off as much of the residue as possible with a razor blade or flat head screwdriver without scratching the surface you are cleaning. Apply mineral spirits or denatured alcohol. Use a scrub pad if possible, unless the surface is easily scratched, then use a sponge. Scrub vigorously.
While most plastics will begin to melt at high temperatures, silicone does not have a melting point and remains solid until combustion occurs. At high temperatures (200-450oC), silicone rubber will slowly lose its mechanical properties over time, becoming brittle.
Temperature. Warmer temperatures generally lead to faster curing times, partly due to the fact that they usually involve higher humidity. However, regardless of the ambient temperature at the time you undertake your project, it's not a good idea to try to help the silicone cure faster by applying direct heat to it.