Karnak - 671 Karna-Seal Silicone Roof Sealant, White, 2.5 gallon

Karnak 671 Karna‑Seal is a single-component, moisture-curing silicone sealant designed for long-lasting exterior performance. With exceptional UV stability and high elasticity, it resists weathering, chalking, and hardening even in ponding water conditions. Rain-safe in just one hour and suitable for both horizontal and vertical applications, Karna‑Seal delivers clean, resilient protection without sagging or the need for mixing.

Key Features

• 100% silicone formula with excellent UV resistance and weather stability
• Moisture-curing and rain-safe in just one hour
• Bonds to a wide range of roof substrates, including modified bitumen, metal, aged single-ply (TPO, PVC), EPDM, spray polyurethane foam, and concrete
• Resists hardening, chalking, cracking, and ponding water
• Silicone-based elastomeric performance with no mixing required

Packaging: 2.5-gallon pail

Solids by weight: 92% nominal; solids by volume: 97% nominal

Elongation: initially 273%; after 1,000 hours weathering: 238% (ASTM D412)

Tensile strength: 161 psi nominal; after 1,000 hours: 156 psi (ASTM D412)

Tear resistance: 34 lbf/in initially; improves to 44 lbf/in after weathering (ASTM D624)

Weight per gallon: ~8.8 lb

Hardness (Shore A): 27 nominal

Coverage: 4–8 gallons per 100 sq ft at 1/16″–1/8″ thickness

Coverage with fabric reinforcement:

• At 1/16″ thickness: approx. 25 ft (4″ fabric), 18 ft (6″ fabric) per gallon
• At 1/8″ thickness: approx. 12 ft (4″), 9 ft (6″) per gallon

Skins over in 5–10 minutes at 77 °F and 50% RH; full cure in ~24 hours

Application temperature: 50 °F to 120 °F

Service temperature (cured film): –75 °F to 385 °F

VOC content: up to 48 g/L (max)

• Clean the surface thoroughly—ensure it is dry and free from oil, dust, or other contaminants. If needed, wipe with a solvent such as denatured alcohol.
• Open the pail and apply directly—no mixing required. For cracks or seams, lay a 1/16″ to 1/8″ layer and embed reinforcing fabric (e.g., 5540 Resat-Mat). Smooth out the fabric and apply a second layer.
• The seal begins curing upon exposure to air—skinning over in about 5–10 minutes.
• For seamless application, use consistent thickness to maintain coverage around 4–8 gallons per 100 sq ft.
• Once applied, the sealant becomes rain-safe in about one hour. Allow full cure over approximately 24 hours before exposure.
• Clean tools with mineral spirits and ensure proper ventilation during use.

Q: Can Karna-Seal withstand standing water or ponding?
A: Yes. It resists permanent ponding water, making it a durable choice for low-slope roofs.

Q: What surfaces can it be used on?
A: It adheres to modified bitumen, metal, aged TPO and PVC, EPDM, spray polyurethane foam, and concrete.

Q: How much sealant is needed for coverage?
A: At 1/16″–1/8″ thickness, coverage is approximately 4–8 gallons per 100 sq ft. Use fabric for reinforced areas.

Q: How quick is it safe in rain?
A: It becomes rain-safe in as little as one hour after application.

Q: What are its elongation and service temp capabilities?
A: It offers high flexibility—273% elongation initially and holds up to –75 °F to 385 °F when cured.