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The Dowsil 781 Silicone Sealant in Black is a versatile, one-part sealant designed for a wide range of non-porous surfaces, offering excellent adhesion and durability for various sealing applications. Its key benefit lies in its superior resistance to aging, shrinkage, cracking, and discoloration, ensuring long-lasting seals. A potential caveat is its acetoxy cure, which may not be suitable for all materials or environments.
| Colour | Black |
|---|---|
| Model Part Number | 3295257/C05 |
| Brand | Dowsil |
The typical shelf life is 12 months from the date of manufacture when stored in its original, unopened container in a cool, dry place.
No, silicone sealants are generally not paintable. Once cured, it's best to leave the sealant exposed or use masking tape during painting.
Yes, it offers excellent weatherability, UV resistance, and temperature resistance, making it suitable for a wide range of exterior applications like weather sealing.
It is tack-free in one hour and has a skin-over time of 14 minutes. Full cure time depends on joint size, temperature, and humidity but typically takes 24 hours or more for complete depth cure.
Yes, it is suitable for general internal sealing and is WRAS approved for contact with potable water once cured. Ensure surfaces are non-porous and clean.
Acetoxy cure silicones, like Dowsil 781, release acetic acid during curing and are generally faster curing. Neutral cure silicones release less odorous byproducts and are often preferred for sensitive materials like natural stone or certain metals.
Dowsil 781 has a joint movement capability of +/-20% of the joint width, meaning it can accommodate expansion and contraction within this range.
Ensure surfaces are thoroughly cleaned, dry, and free from dust, grease, or old sealant. Check that the application temperature is within the recommended range (+5 to +40°C).
Verify application temperature and humidity conditions. High humidity can slow down the curing process. Ensure a continuous bead of sealant was applied, as thin layers may take longer to cure.
Dowsil 781's acetoxy cure releases acetic acid, which can react with certain metals. Ensure compatibility or use a neutral cure sealant for sensitive metals. Clean affected area and consider re-sealing with a compatible product.
This could indicate insufficient adhesion or excessive joint movement. Ensure proper surface preparation and that the joint movement is within the sealant's +/-20% capability. For larger movements, a different sealant might be required.
Setup: Ensure the surfaces to be sealed are clean, dry, and free from dust, grease, and other contaminants. For optimal adhesion, surfaces may require cleaning with a suitable solvent wipe. Apply the sealant using a standard caulking gun. The application temperature range is between +5°C and +40°C.
Compatibility: Dowsil 781 adheres well to non-porous materials such as glass, aluminum, anodized aluminum, painted surfaces, PVC, and composite boards. Due to its acetoxy cure, it is not recommended for use on certain metals (e.g., copper, brass) or alkaline surfaces (e.g., concrete, natural stone) where the acetic acid released during curing could cause corrosion or discoloration. Always test on a small, inconspicuous area if unsure.
Care: Once cured, the sealant is easy to clean. Use a damp cloth to wipe away surface dust or light soiling. For tougher marks, mild detergent can be used. Avoid abrasive cleaners. Ensure adequate ventilation during application and curing as the acetoxy cure releases acetic acid.
