Silicone and Sealant Types — Acetoxy, Neutral and Hybrid Compared

Silicones and sealants used in construction and assembly fall into categories by their chemistry, and each suits different surfaces and applications.

Acetoxy Silicone

Acetoxy-cure silicones give off the characteristic smell of acetic acid as they cure, and they bond fast and hard to glass, ceramic and aluminium. They are the common choice for wet areas — shower enclosures and bathrooms. Because the cure is acidic, though, they can corrode some metals, so they need care on those surfaces.

Neutral Silicone

Neutral-cure silicones release no acidic by-product, which makes them safer on metal and natural stone — surfaces that acid can attack. Where the corrosion risk matters, this is the chemistry to use.

Hybrid Sealant

Hybrid (MS polymer) sealants and adhesives seal and bond at the same time. They grip a wider range of surfaces than silicone — timber, concrete, metal, PVC, glass — and because they can be painted over, they work indoors and out.

Surface Preparation and Joint Geometry

Most adhesion failures come from the surface, not the product. It has to be free of dust, grease and old sealant residue — new silicone does not bond to old silicone. Porous surfaces need a primer; on smooth ones, cleaning is usually enough.

Joint geometry matters just as much. The accepted rule is that a joint should be about twice as wide as it is deep. Too deep, and the material cannot stretch as the joint moves, so it tears away at the edges. Deep joints take a backer rod at the base to limit depth — done for joint life, not to save material.

Calculating How Much You Need

Cartridge count is a volume calculation: joint width (mm) × depth (mm) × length (mm) gives the volume required, and a 280 ml cartridge is 280,000 mm³. On a 10 × 10 mm joint a cartridge runs about 2.8 metres; on a fine 5 × 5 mm joint the same cartridge passes 11 metres.

Besides getting the order quantity right, this is what makes product comparison meaningful — compare cost per metre, not cost per cartridge.

Shelf Life and Storage

Silicones and sealants keep curing slowly even in a sealed cartridge. Shelf life runs from the date of manufacture and is printed on the cartridge. Store them cool, dry and upright. One that has frozen or sat in extreme heat can look normal when opened and have lost its adhesion — which is why stock should be rotated first in, first out.

Choose on four things: the surface, whether the area is wet or dry, the finish you need (colour, paintability), and whether the application is interior or exterior.