How to remove and replace bathroom silicone

If the bead is still stuck down along its whole length and the black is only on the surface, try cleaning it first. Replace it if:

• the edge has lifted or peeled anywhere
• the bead has split or gone hard
• the black is under or inside the sealant, not on top
• water shows up behind or below the joint

If tiles are loose, the wall is soft or water is coming from behind the tiles, fix that first. New silicone won't seal a leaking waterproofing layer.

• A sharp blade or silicone removal tool, and a plastic scraper
• Clean, lint-free cloths and a bathroom cleaner to cut soap film
• Masking tape
• A caulking gun and a cartridge of anti-fungal silicone. One 280 ml cartridge of Pereseal AF runs about 7 m at a 6 mm bead
• A tooling spatula

1. Cut along both edges of the old bead and pull it out in strips. Keep the blade on the sealant. Acrylic trays and enamel scratch easily, and you don't want to cut into the waterproofing behind.
2. Scrape off what's left with the plastic scraper. Every trace of old silicone has to go; new silicone won't bond to it.
3. Clean the joint to remove soap film and any mould. Rinse, then wipe dry.
4. Let the joint dry completely, ideally overnight with a fan or the window open. Sealing onto a damp surface is the most common cause of early failure.
5. For a bath, fill it with water before sealing. The bath settles to its lowest point, so the bead won't be stretched the first time someone gets in.
6. Mask both sides of the joint, leaving the gap where the sealant will go.
7. Cut the nozzle at an angle to about the joint width. Push the sealant ahead of the nozzle in one steady, continuous bead so it fills the gap and touches both sides.
8. Tool it within 5 minutes with a spatula, pressing it into the joint and leaving a smooth, slightly concave face that sheds water.
9. Pull the tape off straight away, before the skin forms.
10. Leave the bath full until the sealant has cured, then drain it.

AF is tack-free in about 15 minutes and cures about 10 mm deep in 7 days. We recommend keeping the water off for at least 24 hours, and longer if the bead is deep or the room is cold and dry. Use another bathroom if you can. How long does sealant take to cure explains why.

AF has a fungicide that stops mould growing in the sealant. Mould still grows on the soap film and water that sit on top of it. Run the fan or open a window after showering, squeegee or wipe the joint, and clean it regularly with a mild bathroom cleaner.

If the black comes back within weeks, or from underneath the bead, water is getting behind it. Read why bathroom silicone turns black before you reseal again.