Dowsil 791 External Weatherproofing Silicone Sealant - 310ml Cartridge

Dowsil 791 Weatherproofing Silicone Sealant is a one-part, low modulus, neutral curing sealant designed for general glazing, and weather sealing in curtain walls & building facades ideal for both commercial and domestic applications. This exterior silicone sealant has exceptional weatherproofing properties it resists extreme temperatures, ozone and UV radiation. Versatile, it provides excellent adhesion to most porous and non-porous surfaces without needing a primer and cures to form flexible and durable joints.

• Ideal for general glazing applications
• Can be used for commercial & domestic applications
• Low odour
• Resists extreme temperatures, ozone & UV radiation
• Available in multiple colours
• Excellent unprimed adhesion to most porous and non-porous surfaces
• Conforms to ISO 11600-F&G-25LM and also meets ISO specification 9047 class 50%

Ensure that all surfaces to be sealed are clean, dry, and sound. Surfaces should be free from frost, dust, grease, old sealants, and any other contaminants that could interfere with adhesion.

• For non-porous surfaces (such as glass, aluminum, or metal), clean and degrease the area using a suitable solvent, such as DOWSIL™ R-40 Universal Cleaner. Apply the cleaner on a clean, lint-free cloth, and wipe down the surfaces thoroughly to remove any oils, dust, or other residues. Allow the surfaces to dry completely before application.
• For porous surfaces (like concrete, brick, or mortar), use mechanical cleaning methods to remove loose particles and contaminants. A steel brush, sanding disc, or other appropriate tools can be used to clean these surfaces effectively.
• DOWSIL™ 791 is designed for good adhesion to most common substrates. However, due to the variety of coatings and finishes that can affect adhesion, it is recommended to test adhesion on a small, inconspicuous area before applying the sealant to the entire joint.
• For optimal adhesion, especially when working with porous surfaces, priming may be required. A primer will help maximize the sealant's adhesion.
• Mask areas adjacent to the joint with tape to prevent contamination of the substrates and to ensure a clean, neat sealant line. It is essential to remove the masking tape immediately after tooling the sealant to achieve a professional finish.
• Always ensure adequate ventilation when using cleaning solvents or when working in confined spaces. Follow all safety precautions as indicated on the solvent labels. Wear solvent-resistant gloves, goggles, and protective clothing as needed.

When back-up material is necessary, use a closed-cell polyethylene backer rod. For joints too shallow for backer rods, use low tack polyethylene tape. Back-up materials provide back pressure and prevent three-sided adhesion, which could limit the sealant’s movement capability.

• Apply DOWSIL™ 791 Weatherproofing Silicone Sealant in a continuous bead using an appropriate sealant gun such as Geocel Cox Skeleton Gun. Ensure a positive pressure is maintained throughout the application for consistent and even coverage. The sealant should be applied to the joint or gap without interruption.
• After application, tool the sealant within 5 minutes to ensure good contact between the sealant and the substrate. Tooling also helps achieve a smooth, professional finish for best results use Bedec Silicone Profilers. The surface should be tooled lightly, ensuring the sealant is pressed into the joint without overworking it.
• Any excess sealant should be cleaned off tools and non-porous surfaces while still in an uncured state using DOWSIL™ R-40 Universal Cleaner. For sealant that has been misapplied to porous surfaces, it should be left until just cured, and then it can be removed using peeling, cutting, or other mechanical means. Be careful not to damage plastic or coated surfaces.
• The width and depth of the joint must accommodate the movement capability of the sealant. Ensure the joint width is designed with the following guidelines.
• Joints between 6-12mm: Seal depth should be 6mm.
• Joints above 12mm: Use a width-to-depth ratio of 2:1. For situations where fillet joints are needed, ensure a minimum of 6mm sealant bite on each substrate.
• Remove masking tape immediately after tooling to prevent it from adhering to the sealant and to achieve a clean edge. Ensure the sealant has been properly tooled before removing the tape to avoid damaging the joint.
• Allow the sealant to cure according to the product’s specifications. Curing time will depend on factors such as joint size, ambient temperature, and humidity levels. Be sure to keep the joint undisturbed during the curing process.

Always follow manufacturers instructions found on the packaging.

Q. What is DOWSIL™ 791 Weatherproofing Silicone Sealant used for?

A. DOWSIL™ 791 Weatherproofing Silicone Sealant is a high-performance, neutral-curing silicone designed for weatherproofing applications. It is typically used to seal joints in areas exposed to outdoor conditions, such as window frames, doors, and curtain walls, to prevent water and air infiltration. It is ideal for sealing nonporous surfaces around construction and building applications.

Q. Can DOWSIL™ 791 be used on both porous and non-porous surfaces?

A. Yes, DOWSIL™ 791 is suitable for both porous and non-porous surfaces, including materials like glass, metal, ceramics, and various plastics. However, a primer may be required for certain porous surfaces, especially in demanding conditions.

Delivery

All orders placed on a working day before 3pm will be dispatched on the same day for next working day delivery. Orders placed before 3pm on Friday will be delivered on Monday (excluding bank holidays). Orders placed on weekends and Bank Holidays will be dispatched on the next working day. All orders have a charge of £3.99 for express delivery. We strongly suggest customers avoid booking tradespeople until they receive their order. Next Day Paint will not be held liable for any costs incurred due to order processing errors, delivery delays, or other issues that may result in financial loss.

Special Delivery

You can now choose some special delivery options. 

• AM Delivery: Get your order by 2pm
  If placed on a working day before 3pm, the AM Delivery will be dispatched on the same day for Next Working Day delivery. 
  Orders placed before 3pm on Friday will be delivered on Monday AM (excluding bank holidays). Orders placed on weekends and Bank Holidays will be dispatched on the next working day for delivery on the following AM. All orders have a charge of £12.99 for AM delivery.

• Late Cut-Off: Get an extra hour to place your order for Next Working Day delivery.
  Orders placed on a working day before 4pm will be dispatched on the same day for Next Working Day delivery. 
  Orders placed before 4pm on Friday will be delivered on Monday (excluding bank holidays). Orders placed on weekends and Bank Holidays will be dispatched on the next working day. All orders have a charge of £5.99 for Late Cut-Off delivery.

• Saturday Delivery: Get your order on Saturday
  Option available on Fridays. Orders placed on Friday before 3pm will be delivered on Saturday. All orders have a charge of £9.95 for Saturday delivery.

Exceptions

We do not deliver to the Channel Islands or the Republic of Ireland

Certain postcodes delivery times and charges may vary please head to the cart to see your available delivery options.

Returns

We offer a 14 day money back guarantee for all goods shipped correctly that are not required. If the item is not required, please send the item back for a full refund in its original condition, unused with its original packaging. Please note return for unwanted item is at your own expense.

Contact us as soon as possible to inform us you will be returning the product either by the contact form below or by calling our team on 0161 960 0217.

Please note that all tinted paint purchases are final and non-refundable, if you are unsure this is your product please check the listing or contact us for details. Once an order is processed and mixed, it cannot be returned or refunded, even in cases of delivery delays or changes in circumstances.

While we strive to meet delivery timelines, we are not responsible for any delays once the product has been shipped. Delivery times may vary due to factors such as courier delays, weather conditions, or other circumstances beyond our control.

We always recommend getting samples or contacting us for free of charge colourcharts. We do our best to represent colours as accurately as possible however screens variations and different surfaces can alter this. Unfortunately in the event you do not like the colour we are unable to accept the product back if they it has been opened.

Damaged Paint

Please visit our damages page where we can help resolve the issue for you. 

Incorrect Item

We will be happy to organise an exchange for the correct goods at no extra charge to yourself, please get in touch to organise this.

Faulty Items

If you find a fault with your product, we can offer a full refund or exchange within 30 days. We test every product that is returned to us, sadly if a product is found to have no fault we cannot refund this and the you will be given the option to have this returned to you. Please get in touch to discuss these options. If you find fault after 30 days of purchase you may wish to contact the manufacturer directly as they will be able to offer support with the product.