How to Seal a Bath or Shower Neatly on Your First Attempt

A silicone bead is either invisible or it is the first thing anybody notices in the bathroom. There is no middle ground and there is no fixing it halfway through — silicone smears rather than corrects.

The good news is that the difficult part is not the application, it is the removal, and removal is just patience.

What you need

• A sealant remover tool or a sharp utility knife
• Silicone remover solvent
• Isopropyl alcohol or methylated spirit
• Masking tape
• One cartridge of sanitary-grade silicone with fungicide
• A skeleton gun
• A sealant smoothing tool, or your finger and washing-up liquid

Time: two hours, of which ninety minutes is removal. Plus 24 hours drying before use.

Remove every trace of the old sealant

New silicone does not stick to old silicone. If you leave a film of the old bead, the new one peels off within months and water gets behind it.

1. Cut down both sides of the bead with a sharp blade, keeping flat against the surfaces.
2. Pull the bead away in one piece if you can. It often comes free in a long strip, which is the most satisfying part of the job.
3. Scrape the residue with a plastic scraper. Do not use metal on an acrylic bath — it scratches instantly and permanently.
4. Apply silicone remover solvent to whatever is left, leave for the stated time, then scrape again. There will be more than you think.
5. Wipe the whole area with isopropyl alcohol and let it dry fully. This removes soap film and the last of the solvent.

Fill the bath first

This matters and almost nobody does it. Fill the bath with water before sealing, and leave it full until the silicone has cured.

A bath full of water drops several millimetres on its feet. If you seal it empty, the first bath you take stretches the joint and tears it away from the wall.

Apply the bead

1. Mask both sides — a strip of tape on the wall and a strip on the bath, leaving a gap slightly wider than you want the final bead.
2. Cut the nozzle at 45 degrees, at a point that gives an opening slightly narrower than the gap. Too big cannot be undone.
3. Work in one continuous pass if you possibly can, pushing rather than pulling the gun, at a steady speed. Stopping and restarting leaves a visible join.
4. Smooth immediately with a smoothing tool, or a finger dipped in water with a drop of washing-up liquid. One pass, firm, in one direction. Going back over it drags the surface.
5. Remove the masking tape straight away, while the silicone is wet, pulling away from the bead at a shallow angle.
6. Leave it alone for 24 hours. Not six. The surface skins within an hour and feels dry, but the depth of the bead is still soft, and using the shower early ruins it.

If it goes wrong

Stop, and remove the whole bead while it is still wet with a scraper and solvent. Do not try to patch it. A patched bead is visible forever and traps water at the join.

Wet silicone comes off cleanly in five minutes. Cured silicone takes an hour. That difference is why it is always worth restarting immediately.