Water will penetrate your bathroom walls and cause expensive damage to your valuable home unless you take precautions with your bathtub. You'll need to make sure that you properly caulk the tub tub to avoid that type of water disaster. Steps Examine the joint between the bathtub and the wall. Clean all old caulk, mildew and soap scum from the edge of bathtub. Be careful not to scratch surface of tub. Wipe with denatured alcohol to clean and remove any moisture from each seam. Rubbing alcohol contains oil that leaves residue (to keep from drying out your skin) and should not be used for cleaning. 2 Use caulk approved for bathroom surfaces. There are choices in color and price. It seems more silicone costs more. Silicone Calk for Kitchen and Bath has a mildew preventer built in it. 3 Apply masking tape to both sides of where you want your new caulk bead, with the edges of the tape lining up to exactly where you want the bead of caulk to stop. This is a technique that pr...