Remove the bath's existing sealant using a utility knife or the flat edge of a standard screwdriver. Hold the utility knife or screwdriver at a low angle and gently scrape away the existing sealant.
Mix mildew cleaner following the instructions on the bottle. Submerge a clean rag into the bucket and thoroughly wipe all the areas where sealant was removed. Allow areas to dry before proceeding.
Cut the tip of a caulk tube containing caulk rated specifically for the bath at a 45 degree angle using a utility knife.
Insert the tube of caulk into a caulking gun. Depress the caulking gun trigger until caulk oozes out of the tip. Wipe the tip clean.
Place the tip of the caulk tube into a seam using a corner as a starting point. Depress the caulking gun handle using constant pressure. Once a bead of caulk is started, move the caulking gun along the seam until a stopping point is reached. Remove the excess caulk by running a wet finger over the bead. Doing so will smooth out the bead giving it a uniform look. Dispose of excess caulk.
Continue caulking until all areas have been caulked. Follow the manufacturer's instructions on the tube of caulk to allow for proper drying time. Not using the bath until the caulk has cured will ensure the bath is sealed and protected against water leakage.