How do I caulk a bathtub or shower properly myself?

Start by removing all old caulk using a caulk remover tool or utility knife, then clean the surface thoroughly with rubbing alcohol or a mold-killing cleaner and let it dry completely. Fill the tub with water before caulking so the tub is weighted down, which prevents the caulk from cracking later when weight is applied. Apply painter's tape along both edges of the joint to get a clean line. Cut the caulk tube tip at a 45-degree angle, load it into a caulk gun, and apply a steady continuous bead along the joint without stopping. Immediately smooth it with a wet finger or caulk tool in one clean stroke. Remove the tape while the caulk is still wet, then let it cure fully before using the shower, usually 24 hours.