How to remove caulk from a shower without scratching the tub

Step by step: how to remove caulk from a shower without scratching the tub

Safety first. Open a window and run the fan. Mineral spirits are flammable, so keep them away from flames and pilot lights, and let rags dry flat outdoors before you throw them away. Never mix bleach with vinegar, ammonia, rubbing alcohol or other cleaners, and rinse one product off before you use the next.

1. 1

   Figure out what kind of caulk you have

   Press the bead with a fingernail. Silicone feels rubbery, stretches and has a slight shine; latex or acrylic caulk is firmer, duller and crumbles when you dig into it. This decides which remover you need later.

2. 2

   Cut along both edges of the bead

   Hold a utility knife at a low angle and slice along the top edge, where the caulk meets the tile, then along the bottom edge on the tub or tray. Keep the blade nearly flat against the tile, not pointed into the tub, so you don’t gouge acrylic or fiberglass.

3. 3

   Pull the old bead out in long strips

   Grab a loose end with needle-nose pliers and pull slowly at a low angle. Silicone often comes out in one long rope. Latex tends to break, so work it out in shorter pieces with a hooked caulk tool.

4. 4

   Scrape off the remaining bits

   Use a plastic razor blade or caulk scraper to shave off the lumps left in the corner and on the tub lip. A metal razor is fine on glazed ceramic tile but scratches acrylic, fiberglass and enamel, so keep it off the tub.

5. 5

   Dissolve the thin film

   Silicone leaves a slick film that new caulk won’t stick to. Rub it with a rag dampened in mineral spirits until the surface no longer feels slippery. For latex caulk, apply a latex caulk remover gel to the leftovers, wait the time on the label (DAP’s takes about 2 hours), then scrape it off.

6. 6

   Treat mold in the joint

   Black spots in the gap or on the tile edge are mold. Wipe the joint with a solution of 1/3 cup bleach per gallon of water, keep it wet for 10 minutes, then rinse with clean water. Don’t use bleach and mineral spirits at the same time.

7. 7

   Vacuum and wipe with alcohol

   Vacuum crumbs out of the gap, then wipe both surfaces with rubbing alcohol on a clean rag to remove soap scum and any solvent residue. The alcohol flashes off in minutes and leaves a clean surface for new caulk.

8. 8

   Let the joint dry completely

   Leave the shower unused with the fan running for at least 24 hours, longer if water got behind the tile. A hair dryer on low speeds up the surface but not the gap. New caulk over a damp joint traps moisture and mold.

Silicone vs latex caulk: what removes each one

Silicone comes out best by cutting and pulling, with mineral spirits for the film; latex softens with a caulk remover gel. Removers are not universal, so check before you buy.

DAP’s Caulk-Be-Gone is a good example: it softens most latex caulks in about 2 hours, but DAP says it is not suitable for silicone, polyurethane or other non-latex sealants.

What to do about mold under the old caulk

Clean and dry it before anything new goes on. Black spots that stay after scrubbing the surface usually mean mold is growing inside or under the caulk, which is often the reason to replace it.

The EPA’s mold cleanup guidance says not to paint or caulk moldy surfaces: clean up the mold and dry the surfaces first. Clorox’s directions for bathroom mold use 1/3 cup of bleach in a gallon of water, kept wet on the surface for 10 minutes, and warn never to mix bleach with vinegar, ammonia or other cleaners.

• If the drywall or backer board behind the joint feels soft or the tile moves, the leak has gone further than the caulk. Call a tile or plumbing pro before recaulking.
• If mold covers grout too, deal with it at the same time using our guide to cleaning shower mold.

How long to wait before recaulking and using the shower

Wait until the joint is bone dry, usually 24 hours, then follow the new caulk’s label for when the shower can get wet. Cure times vary a lot between products.

For example, DAP’s 100% silicone kitchen and bath sealant is listed as 12 hour water ready, while other caulks ask for a day or more. Fill a tub with water before caulking it so the joint is at its widest when the caulk sets, and drain it once the caulk has cured.

Mistakes to avoid

• Using a metal razor or screwdriver on an acrylic or fiberglass tub and leaving permanent scratches.
• Leaving a thin silicone film behind, so the new bead peels off within weeks.
• Caulking over mold or a damp joint, which seals the problem in.
• Buying a latex caulk remover for silicone caulk, where it does almost nothing.
• Using bleach and mineral spirits back to back without rinsing in between.
• Showering before the new caulk has cured for the time on its label.