Caulk is a thick, sticky material that dries into a solid mass. It adheres to the surface where it has been applied and creates a waterproof barrier. It has many applications in building and construction, most involving sealing and finishing surfaces, joints and small separations. Caulk is available in silicone, rubber, latex and oil or resin base. The most common caulk used in bathrooms is silicone.
Reasons to re-caulk around a bathtub include mold and mildew buildup behind the caulk surface and dried out, cracked and peeling caulk. If your tub has caulk that cracks or peels frequently within a year of application, you may have used the wrong type of caulking for the bathroom. Silicone caulk is the most common type of caulking used for watery and moist environments.
Old caulk must be removed and the site cleaned and prepared before new caulk is applied for the best adhesion and appearance. Peel out the old caulk if possible, or use a softening agent to make it easier to remove. When all the old caulk is removed, clean the area with soapy water and rinse it with clear water. Apply a spray of bleach to sanitize the area and kill mold and mildew spores. Let the area dry thoroughly before applying new caulk. Use a mildew-resistant caulk in the bathroom.
How long caulk lasts depends on several factors, including the type of caulk, the preparation and application process and the environmental conditions where it is applied. Improperly applied caulk will allow moisture and mildew in spaces that it is meant to seal, which will discolor the caulk material and require replacement sooner than if it had been properly applied. Caulk around a bathtub should be replaced if it is cracked or peeling or has a lot of mildew growing behind it, indicating leaks in the seal that are allowing moisture in.