How to use and apply a silicone sealant

Silicone sealants are based on silicone polymers and cure to form a tough flexible rubber suitable for both household and industrial applications. While not a “100%” natural material like rubber, food grade silicone is a non-toxic polymer mostly made from silica (sand).

The main types of silicone sealant are:

The acetoxy cure silicone sealants such as BAL Micromax3, derive their name from their release of acetic acid, which gives off a strong vinegar like smell while curing. Because of the acid released acetoxy cure silicones have a stronger smell than neutral cure silicones.

These silicones cure with the presence of atmospheric moisture and generally have a very fast cure time, they create a skin in around 10 minutes, become tacky in 17 minutes and fully cure after 24 hours. As they adhere better to many surfaces, they are most commonly used for internal applications such as sealing gaps around baths, showers, windows and worktops.

They stay flexible at wide temperature ranges, are completely waterproof, and won’t support mildew growth with some like BAL Micromax2 having specific bacteria resistance characteristics.

Acetoxy silicone sealants are not recommended for use on porous surfaces such as limestone, travertine etc. and are not paintable.

Oxime cure sealants are a high-quality, elastic one-component silicone based joint sealant. They are colourfast and UV resistant, anti-mould, neutral curing and can be used externally due to their superior adhesion and weatherproofing properties.

A neutral cure silicone is a sealant which releases alcohol or another non-acidic substance whilst curing, because of this the sealant has virtually no odour. Neutral cure products reduce or eliminate the production of acetic acid while curing, they are popular choices for sealants on sensitive surfaces such as marble, granite and other natural stones.

Neutral cure silicone sealants can also be used on metals, glass, uPVC, metals, wood, aluminium and other substrates where an acetoxy might react and cause discolouring.

(Always check the manufacturers instructions before using)

Before sealing, you'll need to remove any previous silicone from all surfaces (if there is any), read our separate guide on how to do this. Then,  ensure that surfaces are clean, dry and free from dust, grease and contaminants that affect adhesion. Non-porous surfaces should be degreased using white spirit or non-oily solvents and then washed clean and left to fully dry. Any wood should be painted.

Applying a layer of silicone around the edges of the tiles helps further waterproof the area but it also provides a clean, neat finish to your tiles.

Cut the end of the silicone cartridge slightly wider than the sealant gap and place it in a caulking gun. Hold the tip at a 45° angle and apply into the corners etc, by squeezing the caulking gun and working from one end to the other, maintaining an even and consistent amount of silicone. After applying, use a sealant shaper to take off any excess silicone and smooth the edge. Allow to cure for approximately 24 hours per 4mm thickness.

You need to create a nice clean edge otherwise your silicone will 'feather' and this will age the silicone quicker and eventually allow water to penetrate it from underneath. To prevent this there are two ways to help create that neat professional finish.

For ease, spray the Fila Silicone Finisher after you’ve applied the sealant, this will help to reduce overlapping and smudging of the silicone providing the perfect finish. It also helps the sealant dry quicker too.

If you don't have the finisher or it's not in your budget, tape the area (top and bottom) with frogging tape (like you would use in decorating) and silicone in between the two strips. You'll still need to smooth the application but when you remove the tape it should create a clear bold line.