Silicone Weatherproofing Sealant

  • Ideal for expansion, connection, perimeter and other movement joints.
  • Neutral cure – suitable for use on coated glass, galvanized steel, masonry and other porous and nonporous substrates.
  • Extension/compression movement capability of up to ±50 percent of the original joint width.
  • Excellent weatherability, virtually unaffected by sunlight, rain, snow, ozone.
  • Excellent unprimed adhesion to a wide variety of construction materials and building components.
  • Ease of application – ready to use as supplied.
  • Excellent rheology, low string upon gunning

One-part, neutral-cure, RTV silicone sealant Neutral, one-part silicone sealant.


Dow Corning® 791 Silicone Weatherproofing Sealant is a specified, premium performance weather sealing product specifically designed for general glazing and weather sealing in curtain wall and building facades.

Typical Properties

Specification Writers: These values are not intended for use in preparing specifications. Please contact your local Dow Corning sales office or your Global Dow Corning Connection before writing specifications on this product.

Method Test Unit Result
Uncured – As Tested at 50% RH and 23°C (73°F)      
ASTM1 C 639 Flow (sag or slump) inches (mm) 0
ASTM C 603 Extrusion Rate g/minute 140
  Working Time minutes 20
ASTM C 679 Tack-free Time, 77°F, 50% RH minutes 40
  Curing Time at 77° (25°C) and 50% RH days 7-14
  VOC Content2 g/L 31
As Cured – After 21 days at 50% RH and 77°F (25°C)
ASTM D 2240 Durometer Hardness, Shore A points 34
ASTM C 794 Peel Strength lb/in (kg/cm) 30 (5.4)
ASTM C 719 Joint Movement Capability percent ±50
ASTM C 1135 Tensile Adhesion Strength    
  At 25% extension Psi (MPa) 40 (0.276)
  At 50% extension Psi (MPa) 60 (0.414)
1ASTM – American Society for Testing and Materials.Based on South Coast Air Quality Management District of California. Maximum VOC is listed both inclusive and exclusive of water and exempt compounds. For a VOC data sheet for a specific sealant color, please send your request to

Dow Corning® 791 Silicone Weather proofing Sealant is a one-part, neutral cure, architectural grade sealant. It easily extrudes in any weather and cures at ambient temperature by reaction with moisture in the air to form a durable, flexible silicone rubber seal.

How to Use

Please consult the Dow Corning Americas Technical Manual, Form No. 62-1112, for detailed information on state-of-the-art application methods and joint design. Please contact your local Dow Corning Sales Application Engineer for specific advice.


Clean all joints removing all foreign matter and contaminants such as grease, oil, dust, water, frost, surface dirt, old sealants or glazing compounds and protective coatings.


Application Method

Install backing material or joint filler, setting blocks, spacer shims and tapes.
Mask areas adjacent to joints to ensure neat sealant lines. Primer is generally not required on non-porous surfaces, but maybe necessary for optimal sealant of certain porous surfaces. A test placement is always recommended. Apply Dow Corning® 791 Silicone Weatherproofing Sealant in a continuous operation using a positive pressure. (The sealant can be applied using many types of air operated guns and most types of bulk dispensing equipment. Before a skin forms (typically within 15 minutes), tool the sealant with light pressure to spread the sealant against backing material and the joint surfaces.
Remove masking tape as soon as the bead is tooled.

Approvals / Specifications

Meets the requirements of:

ASTM C920 Type S, Grade NS, Class 50, Use NT, M, G, A


This product is available in 6 colors: black, gray, bronze, limestone, precast white and white.

Custom colors may be ordered to match virtually any substrate.

Handling Precautions

Product safety information required for safe use is not included in this document.

Before handling, read product and material safety data sheets and container labels for safe use, physical and health hazard information.

The material safety data sheet is available on the dow corning website at, or from your dow corning sales application engineer, or distributor, or by calling dow corning customer service.

Usable Life & Storage

When stored at or below 30°C (86°F) in the original unopened containers, Dow Corning® 791 Silicone Weatherproofing Sealant has a usable life of 12 months from the date of manufacture. Refer to product packaging for “Use By” date.

Packaging Information

Dow Corning® 791 Silicone Weather proofing Sealant is available in 10.3 fl oz (305-mL) disposable plastic cartridges that fit ordinary caulking guns, 20-fl oz (590-mL) sausages.


Dow Corning® 791 Silicone Weatherproofing Sealant is not approved for use as a structural sealant.

Dow Corning® 791 Silicone Weatherproofing Sealant should not be used:

  • In below-grade applications.
  • When surface temperatures exceed 50°C (122°F).
  • On surfaces that are continuously immersed in water.
  • On building materials that bleed oils, plasticizers or solvents, green or partially vulcanized rubber gaskets or tapes.
  • On frost-laden or wet surfaces.
  • In totally confined joints (the sealant requires atmospheric moisture for cure).
  • If the sealant is intended to be painted (paints do not typically adhere to most silicone sealants).
  • To surfaces in direct contact with food or other food-grade applications.
  • This product is neither tested nor represented as suitable for medical or pharmaceutical uses.
Health & Environmental Information

To support Customers in their product safety needs, Dow Corning has an extensive Product Stewardship organization and a team of Product Safety and Regulatory Compliance (PS&RC) specialists available in each area.

For further information, please see our website, or consult your local Dow Corning representative.

Limited Warranty Information – Please Read Carefully

The information contained herein is offered in good faith and is believed to be accurate. However, because conditions and methods of use of our products are beyond our control, this information should not be used in substitution for customer’s tests to ensure that our products are safe, effective, and fully satisfactory for the intended end use. Suggestions of use shall not be taken as inducements to infringe any patent.

Dow Corning’s sole warranty is that our products will meet the sales specifications in effect at the time of shipment.

Your exclusive remedy for breach of such warranty is limited to refund of purchase price or replacement of any product shown to be other than as warranted.



A 20-year Weatherseal Limited Warranty is available. Some testing may be required. Consult your Dow Corning Sales Application Engineer for details.

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