Removing old sealant is the part of a reseal most people rush, and it is the part that decides whether the new bead lasts. New silicone does not bond to old silicone. If a thin film is left on the tile or the bath edge, the new bead will sit on top of it and lift. This guide covers the tools, the method and the surfaces to be careful with.
Before you start
Check what you are dealing with. Soft, rubbery bathroom silicone that is a few years old is a routine job. Hard, brittle or tar-like mastic is different, especially around windows, in older commercial buildings or anywhere built before 2000. HSE notes that some older mastics and sealants can contain asbestos (HSE asbestos guidance). Don’t scrape or cut a material like that yourself. Read our guide on asbestos in old mastic first.
For ordinary bathroom and kitchen silicone, you need:
- A sharp utility knife or a sealant removal tool
- A plastic scraper (essential on acrylic baths and trays)
- A silicone remover gel or solvent, if residue is stubborn
- Clean cloths and a suitable cleaner to degrease the joint
Step 1: cut along both edges
Run the blade along the top edge of the bead, where it meets the tile, and then along the bottom edge, where it meets the bath, tray or worktop. Keep the blade flat and shallow. You are cutting the sealant’s grip, not digging into the joint.
On acrylic and enamelled surfaces, take extra care. A slip with a metal blade can leave a scratch that is far harder to fix than the sealant. If in doubt, use a plastic tool on the bath side.
Step 2: pull the bead out
Once both edges are cut, lift one end of the bead and pull it slowly along the joint. Good silicone often comes away in long strips. Where it tears, start again from the new end.
Look inside the joint as you go. If someone has sealed over old sealant before, you may find a second layer underneath, often with mould between the two. We found exactly that on a 1950s terrace in Three Bridges, where both layers had to come out. Both layers need to go, because new silicone can’t bond to either of them.
Need it done properly? Mr Mastic covers the South East, London and Scotland, with a one-year guarantee on every job. Call or email for a quick quote.
Step 3: deal with the film left behind
After the bead is out, a thin, almost invisible film usually remains on the tile and bath. This is what most DIY reseals miss. Scrape it gently with a plastic scraper, then use a silicone remover if it won’t shift. Follow the instructions on the product, as some need time to soften the residue.
Run a fingertip along the surface. If it still feels slightly rubbery or slippery, there is film left. Keep going until it feels like clean tile and clean bath.
Step 4: clean, treat and dry
Once the old sealant is gone, clean the joint to remove soap, grease and solvent. If there was black mould in the old sealant, treat the joint with a mould remover and rinse it as the product directs.
Then let the joint dry fully. This can take longer than you expect, especially if water has been getting behind the old bead. Sealing onto a damp joint is one of the most common reasons a new bead fails early. Our step-by-step guide to resealing a bath covers the next stage.
When to call someone in
Removal is slow and fiddly, but it is usually doable. It is worth getting help if the bath or tray is a fragile or expensive finish, if the sealant has been built up in several layers, or if water has clearly been getting behind it. Our remedial sealant service covers removing failed and badly applied sealant and finding where water has been getting in.
Quick answers
Can I use white spirit to remove silicone?
Solvents can help lift residue on some surfaces, but they can damage others, including some plastics. Test a hidden area first and follow the product’s instructions.
Will a hairdryer soften old silicone?
Gentle warmth can make some sealants easier to pull, but take care on acrylic and near plastic fittings. Most silicone comes out with a blade and patience.
Do I need to remove all of it?
Yes. New silicone won’t bond to old silicone, so any film or strip left behind is a weak spot where the new bead can lift.
Related services
More advice
- Can You Put New Silicone Over Old Silicone?
- How to Reseal a Bath (and When to Call a Pro)
- Could Old Mastic Contain Asbestos?
- All advice
This guide is general information about sealant work. It isn’t legal, fire-safety or structural advice; for those, speak to a qualified professional.