How to caulk a bathtub edge cleanly
The trick is in the prep, not the application. Old caulk left behind ruins every new bead.
Riley Brand
January 31, 2026
Remove old caulk completely
Use a caulk-removal tool ($5) to slice along both edges, then peel out the old bead.
Scrub the surface with rubbing alcohol or vinegar to remove residue. Dry completely — water in the joint = mold under your new caulk.
The application
Use 100% silicone caulk for tubs (acrylic latex is fine for low-moisture areas). Cut the tube tip at a 45° angle, hole about 1/8 inch wide.
Run a single continuous bead along the joint. Slow and steady. Move in one direction; don't try to fix as you go.
Smoothing
Dip your finger in soapy water. Run it along the bead in one smooth stroke. Wipe excess on a paper towel.
Don't keep going over the same area — once smoothed, leave it alone. Let cure 24 hours before getting wet.
People also ask
What about caulk strips (peel-and-stick)?+
Easier, but they peel up over time, especially in heat and humidity. Real silicone lasts 5–10 years.
Why does my caulk turn black?+
Mold. Either water seeped under the bead, or you used non-silicone caulk in a wet area. Re-caulk; this time confirm 100% silicone.
Painter's tape — does it help?+
Yes. Tape both sides of the joint, caulk, smooth, then peel tape while caulk is still wet. Cleanest line possible.