I re-caulked my bathtub three times in two years before I figured out what I was doing wrong. The first time, the caulk peeled off in sheets after a month. The second time, mold grew behind it because I caulked over a wet surface. The third time, I finally learned the right sequence — and that caulk job is still holding strong four years later.

Step One: Remove All the Old Caulk

Do not caulk over old caulk. It will not bond, and water will get trapped between the layers. Use a utility knife and a plastic caulk removal tool to scrape out every bit of the old bead. Work slowly — gouging the tub surface with the knife creates scratches that trap dirt forever.

For stubborn residue, apply caulk remover gel (sold at any hardware store for a few dollars). Brush it on, wait the time on the label, and the old caulk scrapes off like softened butter.

Step Two: Clean and Dry Completely

Wipe the joint with rubbing alcohol on a rag. This removes soap residue, oils from your skin, and any remaining caulk remover. The alcohol evaporates fast and leaves no residue. Then point a fan at the joint for an hour — or better, do not use the shower for 24 hours before you caulk. Any moisture behind the new caulk guarantees mold.

Step Three: Fill the Tub Before Caulking

This is the trick nobody tells you. Fill the bathtub with water before you apply the caulk. A full tub weighs hundreds of pounds and pulls the tub away from the wall slightly. If you caulk with the tub empty, the joint is compressed. When you fill the tub later and it pulls down, the caulk stretches and eventually tears.

Apply the caulk with the tub full. Smooth it with a wet finger. Let it cure for at least 24 hours — check the tube for the exact cure time. Then drain the tub. The caulk will be slightly compressed when the tub is empty and properly stretched when it is full.

Use the Right Caulk

Buy 100% silicone caulk labeled for kitchen and bath. Not acrylic. Not “siliconized” anything. Pure silicone. It costs a few dollars more but stays flexible and waterproof for years. Acrylic caulk hardens, cracks, and grows mold within months in a wet environment.