How to Remove Silicone Mastic From Baths and Basins etc

Sealant, often referred to as silicone, mastic or mastic sealant is a waterproof flexible, rubber-like material that is applied to baths, sinks and kitchen worktops.

It’s also used outside, usually around Upvc window frames and plastic roofline boards such as fascias, soffits and bargeboards.

This page contains a guide on how to remove mastic sealant from a bath and how to reseal it professionally so it lasts for years to come.

You can also apply our guide to any other surface, from sinks and worktops to window and door frames.

If you want to remove mastic silicone, this guide is for you.

Tools You’ll Need To Remove Mastic/Silicone

While a Stanley knife is sharp enough to cut out and remove mastic sealant, there’s a very real chance of it slipping and damaging the bath.

Instead, we recommend using a scraper, preferably a plastic one.

If you’re still concerned about scratching the bath, you can use masking tape to protect it.

Here are two photos showing how a scraping tool works:

Tool to remove sealant

List of Tools We Recommend

Here’s a list of all the tools we think you’ll need to remove mastic then and re-seal a bath professionally:

How to Remove Bath Silicone Sealant

If you’re using masking tape to protect the bath, first apply this to the edge of the bathtub:

Now use the scraper tool to gently remove as much of the silicone as possible.

You won’t be able to remove all of it but you should aim to remove as much as you can without damaging the bath.

Mastic and silicone removal tool

Use this cheap tool to remove silicone. It’s made from plastic so didn’t scratch the bath or tiles

Removng bath silicone

The tool removed most of the silicone in less than 5 minutes.

Mastic removal tool

This tool made light work of removing the silicone, even though it was stuck to the bath very well

Now you’ve removed most of the sealant, use the removal fluid to loosen up any that remains.

Unibond silicone removal gel

Next spread this gel over the remaining sealant and leave for three hours

Once all of the sealant has been removed, the entire area should be thoroughly cleaned and dried with the tissue.

It’s essential that the bathtub is bone dry.

Next, rub done the area with a tissue and a small amount of white spirit. This is to remove the silicone remover gel, we don’t want it to remove the new silicone!

Sealant removed

The bathtub is now ready to be re-sealed.

(There are more photos further down the page)

Difference Between LMA, LMN and HMA Silicone Sealers

If you choose the wrong sealant then one of the following will happen:

  • it will fade and turn yellow over time
  • it will peel off
  • green and black mould will grow on it after a few months

To prevent this from happening, you should choose your sealant carefully:

LMA (Low Modulus Acetoxy) is a general-purpose mastic sealant that can be used indoors and outdoors. It works best on smooth non-porous surfaces. Low modulus means it’s very flexible.

LMN (Low Modulus Neutral) is often used outdoors around window frames, doors and on roofline fascias, soffits and bargeboards. It has better adhesion than Acetoxy on porous materials such as bricks, blocks and concrete.

HMA (High Modulus Acetoxy) can be used in bathrooms and kitchens. It isn’t as flexible as the other two options and will dry to form a harder sealant. This makes it more suitable for rigid structures that don’t flex such as gaps between tiled walls, sturdy cast iron bathtubs and the like. It doesn’t stick so well to porous materials such as bricks and blocks.

I recommend using LMN outdoors on window frames.

For baths and showers, HMA is generally best. Although if your bath is made from very thin and flimsy plastic, an LMA might be best as it’s more flexible.

All sanitary mastic sealants should contain a fungicide to prevent mould growth.

For general-purpose sanitary sealing such as baths, sinks and shower units, Dow Corning 785 is a great option.

Just choose your colour carefully, it comes in grey, clear, white and several other colours too.

Bath sealant

Available on Amazon

See Dow Corning Reviews on Amazon (5 star rating)

How To Silicone Seal A Bath Like A Pro

Just follow these steps and take a look at the photos:

  1. Ensure the edge of the bath is bone dry and will remain so for at least the next 24 hours (that means no bathing or showering for 24 hours).
  2. Fill the bath with cold water up to the halfway point. This is ESSENTIAL if you have a flimsy plastic bath that flexes. If you don’t do this, when you go to fill the bath for the first time, the mastic may tear or split as the bath flexes under the weight of all the water.
  3. Choose the best sealant for the task (see notes above).
  4. If you’ve never used a mastic gun before, go and practice somewhere else, perhaps under the sink in your kitchen or under the stairs, anywhere where it’s hidden from view.
  5. Cut the nozzle at an angle with a sharp Stanley knife (see photos).
  6. Apply masking tape if you are worried about making a mess (optional).
  7. Apply the mastic by squeezing the trigger smoothly and consistently.
  8. You can smooth off the mastic with saliva on your finger, the more saliva the better but make sure you don’t put your finger in your mouth as the silicone may be harmful if swallowed.
  9. Leave the window open for ventilation and avoid showering/bathing for the next 24 hours.


Here’s a selection of photos I took while sealing a bathtub in the house I recently purchased:










Dow Corning 785:

Dow Corning 785

Cut the nozzle at a 45° angle with a 5-8mm hole for the silicone to come through.

How To Remove Silicone – Conclusion

It took me less than 10 minutes to remove silicone with the removal tool.

I then applied the mastic removal gel and waited for three hours before spending around 5 minutes removing the final traces of silicone and rubbing the area down with tissue and white spirit.

Resealing with mastic only took a few minutes, but I have many years of experience using silicone guns.

If you’ve never used one before, I strongly suggest you practice somewhere else first, it looks easy but it can get messy if you don’t have a steady hand.


Don’t Want To Do This Work Yourself?

I think it’s easy to remove silicone and reseal a bath, basin or worktop but if you don’t want to do this work yourself, hit the button below and you can get a quote from one of our partners:

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