When caulk becomes discolored or mildewed, it's time to recaulk your bathtub. Caulk seals the bathtub to the surround, stopping water from seeping through the joint and entering the wood and wallboard behind the tub. If caulk is damaged so that it doesn’t stop water, the result will require expensive repair. Taking time to recaulk your tub every few years will save you a great deal of headache and labor.
Step 1 - Remove Old Caulk
Begin with a razor blade utility knife. Cut away existing caulk as much as you can. Start by loosening a piece of caulk, then pull. Sometimes you are able to remove a great deal of caulk in this way.
Once you have removed as much as possible, use a caulk or grout-removing tool to get most of the remaining caulk. These tools have a serrated blade at the end of a thin bar that is bent at a 45 degree angle. These tools are highly effective for reaching into the joint and removing old grout and caulk.
Step 2 - Try Caulk Remover
There are commercial caulk removal products that claim to soften caulk and ease its removal. These products may work for you, but they are not always effective. Read the label and see if the remover works on silicone caulk or only on water based caulk. Most of the caulk used in bathrooms in the past decade is silicone based, so a water-based caulk remover will do nothing to help remove it.
If you do use a caulk remover, apply it to any remaining caulk, allow the remover to sit on the caulk for two to three hours, then attempt to scrape it off.
Step 3 - Clean Surface
Before you start to recaulk, you need to have all remnants of caulk removed and have a clean surface so the new caulk will adhere to it properly. Use a razor blade knife with a sharp, new blade. Hold it at a 45 degree angle so that it does not scratch the finish on your tub. Scrape off any remnants of caulk.
Once all the caulk is removed, clean the surface thoroughly. Use rubbing alcohol to remove any oil and dirt from the surface. If you have mildew or mold, wear rubber gloves and use a mild bleach solution (¼ cup bleach to a gallon of water) or a bathroom cleaner with bleach to clean off the mildew. Avoid powdered cleansers that require you to use water, since you don’t want any water seeping behind the bathtub.
Step 4 - Mark with Painter’s Tape
Use painter’s tape to keep your caulk even and smooth. Install the painter’s tape ¼-inch above the seam and just below the seam on the bathtub. This will allow you to apply the caulk without stopping frequently to wipe off excess and reapply.
Step 5 - Fill Tub
Filling the tub with water puts all the weight on the seam that you will ever have, allowing you to fill the entire seam with caulk. This also helps prevent splitting and gapping in the caulk later.
Step 6 - Apply the Caulk
Put a caulk tube into a caulk gun. Cut the stem at a 45 degree angle to give approximately a ¼-inch bead of caulk.
Beginning in a corner, run a thin bead of caulk so that it completely fills the seam, then has a small excess on the outside of the seam. Run the caulk gun over the caulk to smooth and finish the seam. Put the 45 degree angle against the seam and pull the caulk gun away from the point.
Keep a steady pressure on the trigger of the caulking gun until you reach the next corner. Smooth the caulk and begin on the next seam.
Step 7 - Clean the Gun
At each corner, stop to clean the tip of the caulk gun. Wipe with a lint-free cloth so that you begin each line of caulk with a clean bead. Repeat steps 6 and 7 with each seam.
Step 8 - Smooth the Caulk
Either use a dampened caulk finishing tool to smooth the caulk, or you can use a damp finger to accomplish the same task. Create a smooth surface around the tub, using care not to gouge into the caulk and leave a hole.
Step 9 - Remove the Tape
Allow the caulk to set for 20 to 25 minutes, then carefully pull the painter’s tape off of the wall and the tub. Pull up on the tape at a 45 degree angle. Bunch the tape up in your hand as you pull, so that there is only a few inches being pulled up at a time. Use care so that you do not damage your new caulk.
Step 10 - Allow the Caulk to Cure
Don't use the tub for at least 24 hours so the caulk can set completely. It shouldn't contact water during this time.
Reapplying caulk is an easy process. Inspect all of your bathroom caulk on a regular basis, and recaulk as necessary to prevent water damage and expensive repairs.