How to clean uncured caulk from a caulk gun varies depending on the type of sealant used. Latex caulk is easily cleaned with warm water, but silicone caulking is nearly impossible to completely remove from the caulk gun. Both become difficult to remove after they have cured, and for this reason it is always better to remove the sealant as early as you can.
Place the caulk gun in warm soapy water if you have been using latex caulk and wipe the caulk gun down with a soaked rag to remove any water-based sealant. If you were using silicone-based sealant, wipe down the caulk gun with a dry rag to remove the majority of the caulk from the caulk gun.
Put on your leather work gloves after you are done using the water on the caulk gun.
Slide the blade of the utility knife under cured sealant and push the utility knife away from you to cut off large pieces of caulk. Pay close attention to the plunger that inserts into the gun as it is prone to being covered with cured sealant.
Scrape the plunger, plunger rod and caulk tube holder with the 2-inch steel putty knife to remove smaller areas of cured sealant.
Remove remaining sealant from the caulk gun by rubbing over the cured caulk with your fingers.
Wipe the loose pieces of cured sealant from the caulk gun with a clean rag. Do not leave small pieces of caulk on the plunger rod, as this can cause the caulk gun to jam while in use.