To recaulk a bathtub so it lasts, remove every trace of the old caulk, clean off any mold, let the joint dry completely, tape both edges, run one continuous bead of 100% silicone, smooth it within a few minutes, pull the tape, and keep water off it for the time on the tube. Caulk that peels or turns black within months almost always went over old caulk, mold or a damp joint. The bead itself is rarely what failed.
We say that with some confidence because the maker of one of the most common bathroom sealants says the same thing in its own instructions, and the EPA's mold guidance draws the same line. Most recaulking jobs fail in the preparation, not the application.
Why new caulk peels, and what each failure tells you
Before buying anything, look at how the last bead failed. It tells you which step to take more seriously this time.
| What happened | The likely cause | What to change |
|---|---|---|
| Lifting in strips along the tub edge | Caulked over old caulk or soap film, so nothing bonded | Strip everything, clean, dry, then redo |
| Black spots under clear or white caulk | Mold that was sealed in, or moisture trapped behind | Remove, clean and dry fully before recaulking |
| A gap opening after a few baths | The joint moves as the tub fills, or the bead was too thin | Caulk with the tub loaded, and tool the bead into the joint |
| Cracking and going hard | Acrylic or latex caulk in a wet area | Use 100% silicone rated for kitchen and bath |
| Wet or soft wall behind the caulk | A leak or failed backing, not a caulk problem | Stop and have it assessed |
What you need
- 100% silicone sealant labeled for kitchen and bath use, in a matching color.
- A caulk gun.
- A plastic caulk removal tool, and a utility knife used with care.
- Rubbing alcohol and clean lint-free cloths.
- Painter's tape.
- Gloves, and a way to ventilate the room.
On the product, GE Sealants' own guide, how to recaulk your bathtub, read on 2026-09-11, is blunt: if it's not 100% silicone, it won't last in a bathroom. Acrylic and latex caulks have their place, mostly on painted trim, but not in a joint that gets wet every day.
Step 1: take out all of the old caulk
This is the step that decides whether the job lasts. New silicone does not bond to old silicone, soap residue or mold.
Slice along both edges of the old bead with the removal tool, then peel it out in lengths. On acrylic or fiberglass tubs, stay with plastic tools, since a metal blade can scratch the finish. Chemical caulk softeners exist and can help with stubborn residue. If you use one, follow its label, ventilate the room, and do not use it alongside any other cleaning product.
When the bead is out, feel the joint. A thin film of old silicone is often left on the tile and the tub. Scrape it off. If you can feel it with a fingertip, the new caulk will stick to that film instead of the surface.
Step 2: deal with mold before it gets sealed in
If there is black growth in the joint or behind the old bead, it has to go before new caulk goes on. The EPA's brief guide to mold, moisture and your home, updated February 2026 and read on 2026-09-11, says to scrub mold off hard surfaces with detergent and water and dry completely, and it states the rule for this job plainly: do not paint or caulk moldy surfaces.
If you use a bleach product on staining, use it alone and rinse it off. The same EPA page warns never to mix chlorine bleach solution with cleaning products that contain ammonia, because toxic fumes could be produced. Plenty of bathroom cleaners contain ammonia, which is how people end up doing this without meaning to. One product at a time, rinse between them, and keep the window open.
The EPA also sets a size limit. If the moldy area is less than about 10 square feet, it says, in most cases you can handle the job yourself. More than that, or mold coming back through the wall, is a moisture problem that needs a professional assessment, not a tube of sealant.
Step 3: dry it properly
GE's guide puts it in one line: let the surface dry fully before moving on, because moisture under fresh sealant ruins adhesion and invites mold later.
GE suggests wiping the joint with rubbing alcohol, which lifts leftover soap film and evaporates. Then give the joint real time. A bathroom that was showered in this morning is not dry, even if the surface looks it. Leaving the room unused for several hours with the fan running or a window open, or overnight, is the cheap insurance here.
Step 4: consider loading the tub first
A tub flexes slightly when it is full of water and a person, and the joint between tub and wall opens a little each time. A common installer practice is to fill the tub with water before caulking, so the joint is sealed at its widest, and to leave the water in until the caulk has cured. It costs a tubful of water and it is optional, but it answers the "gap after a few baths" failure directly.
How to recaulk a bathtub: tape, bead, tool
- Tape. GE's instructions are to apply painter's tape about 1/8 inch from each side of the joint and press it down firmly so sealant cannot creep under it. The gap between the two tapes becomes your finished bead.
- Cut the nozzle small. You can widen the opening; you cannot shrink it.
- Run one continuous bead. GE's wording is to lay a steady, continuous bead, keep even pressure, and try not to stop mid-line. Stopping and restarting leaves a lump and a weak point.
- Tool it within minutes. Smooth the bead with a smoothing tool or a gloved fingertip, pressing it into the joint. GE says to shape it before the sealant starts to skin, within a few minutes, and names waiting too long to smooth the line as a common mistake.
- Pull the tape straight away, while the silicone is still wet, peeling it away from the joint at a low angle.
On a long run, work one wall at a time so each section is tooled before it skins.
Step 5: keep water off it
Cure time depends on the product, and the figure on your tube is the one that counts. GE's guide gives water-ready in 30 minutes and full cure at 24 hours, and says to avoid touching or exposing the seal for those 24 hours.
If the household can manage it, we would give it the full 24 hours before anyone showers. If you filled the tub first, drain it only after the full cure.
The same job at a kitchen or bathroom sink
The method is identical at a sink: the countertop-to-backsplash joint, or the rim of a drop-in sink. The failures are the same, with one addition. Kitchen joints are greasy. Cooking film on a backsplash will stop silicone bonding as surely as soap scum does, so degrease first. Cleaning grease off a backsplash without ruining the grout covers that step, and the same one-product-at-a-time rule applies.
Around a sink, hard-water scale can also sit along the joint as a white crust. It has to come off before new sealant goes down. If it keeps reappearing, the signs of hard water in the house help you confirm what you are dealing with.
Where this stops being a caulk job
Caulk seals a joint. It cannot fix what is behind it. Stop and have the problem looked at if you find:
- A soft, spongy or bowed wall next to the tub, or tiles that move when pressed.
- Water staining on the ceiling below the bathroom.
- Mold that returns through the grout or wall soon after cleaning, or covers more than the EPA's roughly 10 square feet.
- A tub that flexes or rocks noticeably when you step in.
- Cracks in the tub itself.
Each of these points to water getting past the surface. Recaulking over it seals the moisture in, which is the opposite of what you want. A leak inside the wall, at the drain or at the valve is a licensed plumber's job, and a failed wall behind the tile needs a contractor.
How often to check it
Look at the tub and sink joints whenever you do a seasonal deep clean; the seasonal end of our realistic kitchen cleaning schedule is a natural moment to check the kitchen side. Once a section of bead is lifting, water can get behind it. Strip and redo the whole joint rather than patching over the gap, since new silicone will not bond to the old.
FAQ
Can I put new caulk over old caulk? No. New silicone does not bond reliably to old caulk, and anything trapped behind it, including mold and soap film, stays there. Remove the old bead completely.
Why does my bathtub caulk keep turning black? Usually because mold was sealed in behind the new bead, or the joint was not fully dry when it was caulked. The EPA's advice is not to caulk moldy surfaces: clean, dry, then seal.
How long before I can shower after recaulking? Follow the time on your tube. GE's guide for its silicone gives 30 minutes to water-ready and 24 hours to full cure, and waiting for the full cure is the safer choice.
Should I use silicone or acrylic caulk around a tub? Silicone labeled for kitchen and bath. GE's own guide says that if it's not 100% silicone, it won't last in a bathroom.
The short version
Strip it, clean it, dry it, tape it, run one bead, tool it fast, and leave it alone until it cures. And if the wall behind the joint is soft or the ceiling below is stained, the caulk was never the real problem.
