Silicone caulk will typically be dry to the touch in one to two hours. This allows you to begin cleanup without having to worry about smearing the caulk. However, the caulk will need an additional day or two to fully "cure," which means you should not use your tub, shower or sink until that time.
Allow Three Days in Dryer Climates
Unlike many other products, such as paint, glue and latex caulk, silicone caulk actually uses moisture in the air to cure. Therefore, in dryer climates, give the caulk three days to properly cure.
Generally, silicone caulk will completely dry and cure in 24 hours; however, if you live in a dry climate, give the caulk an extra day or two to properly set.