Matt Seal S-350 Sanitary Silicone Sealant

Matt Seal S-350 Sanitary Silicone Sealant is a neutral-cure, mould-resistant silicone with a low-sheen matt finish for modern bathrooms, showers, kitchens, laundries and other tiled wet areas. It is designed for projects where a traditional glossy silicone bead would stand out against matt tiles, grout, fixtures or contemporary interior finishes.

Available in Arctic White and Ebony, S-350 combines the practical wet-area performance of a sanitary silicone with a deliberately understated finish. It cures to form a permanently flexible waterproof seal and contains added fungicide to help inhibit mould and biological growth in hot, humid environments.

Matt bathroom silicone for modern tiled wet areas

Use Matt Seal S-350 around shower walls and floors, tiled corners, baths, basins, sinks, kitchen and laundry joints, splashbacks and other wet-area interfaces where both performance and appearance matter. Its matt surface reduces the visual contrast between the sealant bead and low-sheen tile or grout finishes.

Why choose Matt Seal S-350?

• Dedicated matt finish: designed to blend more naturally with contemporary tile, grout and low-sheen finishes.
• Mould-resistant sanitary formulation: added fungicide helps inhibit mould and biological growth.
• Neutral oxime cure: non-corrosive to compatible metals and suitable across common wet-area materials.
• ±25% movement capability: remains flexible through normal joint expansion and contraction.
• 300% elongation: provides high stretch capacity before rupture.
• UV stable and colour fast: suitable for internal and external sealing.
• Service temperature: -50°C to +150°C after cure.

Compatible substrates

Matt Seal S-350 is suitable for glazed and unglazed ceramic tiles, glass, porcelain, fibreglass, laminated kitchen benches, timber, aluminium, stainless steel, Colorbond, Zincalume and galvanised metal. Stone surfaces require stain testing before use.

Joint design and application

Surfaces must be sound, dry and clean before sealing. Concrete should cure for at least 28 days. Where possible, design joints to approximately a 2:1 width-to-depth ratio and use backing rod to control deeper joints and prevent three-sided adhesion.

Apply between 5°C and 40°C and tool the bead before the surface skins. The sealant typically skins in around 15 to 20 minutes and cures at approximately 2 mm per day at 25°C and 50% relative humidity.

Important limitations

• Do not use in swimming pools, aquariums or for underwater application.
• Do not use for structural glazing, mirror bonding or on polycarbonate sheeting.
• Do not use in totally confined spaces where atmospheric moisture cannot reach the sealant.
• Do not use on trafficable horizontal joints subject to abrasion.
• Test natural stone for staining before use.
• The sealant may discolour copper and brass.
• Matt Seal S-350 is not paintable.

Matt Seal S-350 or S100?

Choose Matt Seal S-350 when you specifically want a low-sheen sanitary silicone in Arctic White or Ebony.

Choose Adheseal S100 for the broadest colour choice and an established gloss sanitary silicone for general bathrooms, showers, kitchens and tiled wet areas.

Compare the full Sanitary Silicone Sealants range.