670HS Karna-Sil Ultra (High Solids Low VOC Silicone Coating)

670HS Karna-Sil Ultra (High Solids Low VOC Silicone Coating)

Available in: 5 gallon pails & 50 gallon drums

Karnak 670HS Karna-Sil Ultra is a white, single component, high solids, moisture curing silicone coating that produces a durable elastic coating with  exceptional weathering and water resistance characteristics.



Cool Roof Rating Council (CRRC)
1. Solar Reflectance: Initial 0.87 3 year 0.70
2. Thermal Emittance: Initial 0.89 3 year 0.90
3. SRI:
Initial 110 3 year 86


VOC: 50 g/L MAX


Coverage Calculator

  • 1.5-1.5 Gallons per 100sf**


This is intended as a general guideline only, coverage can vary based on many factors.


Newly Sprayed Poly-Urethane Foam or Previously Coated Silicone roofs
(No Primer required): Apply 670HS Karna-Sil Ultra directly over newly sprayed polyurethane foam, or pressure-washed, clean and dry Silicone coated roofs.

Metal, BUR (Built-Up), Modified Bitumen, Concrete, Masonry, TPO, PVC, Hypalon, and EPDM roofs (Requires Epoxy Primer): Pressure-wash roof, and let dry prior to primer application. Apply 180 Karna-Sil Epoxy Primer and allow to cure before applying 670HS Karna-Sil Ultra. 670HS may be used on vertical as well as horizontal applications. All surfaces must have positive drainage. Note: Vertical application may require multiple coats to achieve desired film thickness.

Physical Properties

Weight per Gallon: 10.7 lbs.
Solids by Weight: 96% ASTM D-1644
Solids by Volume: 96 % ASTM D-22697
Color: White
Reflectivity Initial: 0.87 ASTM C-1549
Aged: 0.70 ASTM C-1549
Emissivity Initial: 0.89 ASTM C-1371
Aged: 0.90 ASTM C-1371
Initial SRI: 110
Aged SRI: 86
Hardness Shore A: 50 ASTM D-2240
Elongation: 192% at 73°F ASTM D-2370, 216% at 0°F ASTM D-2370
Tensile Strength: 331 PSI at 73°F ASTM D-2370, 432 PSI at 0°F ASTM D-2370
Application temperature: 40°F and rising
Storage temperature: 50°F – 90°F. Dry environment
Permeance: 5.9 perms ASTM E-96
Service Temperature: -15°F to 180°F
Cure Time: 2-8 hrs. (Temp. & Humidity Dependent)

Preparation & Application

Surfaces to be coated should be dry, clean, and free of dirt, dust, grease, oil and loose rust or coating. Recommended application temperature is 50°F to 120°F. Power wash surfaces with 799 Wash-N-Prep Roof Cleaner or 507 SPC Primer/Wash (EPDM Only) and water. Wash roof surfaces with a minimum of 2000 psi. taking all necessary precautions to avoid damage to the roof system. Patch and repair all seams, flashings, damaged areas, leak and cracks with 502MS Karna-Flex, 505MS Karna-Flex WB, 550 Patch-N-Go self-sealing tape or appropriate sealants or caulking materials.

670HS Karna-Sil Ultra should be applied in a single coat application at the required application rate. If additional coats are to be applied, allow previous coat to cure 2-8 hours (dependent upon temperature and humidity) before applying subsequent coat. Subsequent coats should be applied within 24 hours of previous application to ensure uniform adhesion. Applied coating film should be even and free of pinholes. Coverage will vary depending on the surface to be coated. To improve aesthetics, impact resistance and toughness of the coating, ceramic roofing granules should be applied immediately into the final coat after application. Back-roll granules into coating and allow to cure then blow off or sweep loose granules from the surface. Mix coating prior to application with a 3″ diameter mixer (5-gallon pail) or 6″ diameter mixer (50 gallon drum). Once product is mixed, the entire container should be used. 670HS Karna-Sil
Ultra may be applied by brush, roller or airless spray equipment. Apply at temperatures 50°F to 120°F. Do not apply if rain is expected within 24 hours after application. Commencement of work by the contractor implies their approval of the roof surface. See listing at www.nsf.org for application and cure instructions for rainwater catchment use.


For spray application, a high-pressure airless spray unit with a minimum of 3500 psi working pressure at the gun tip should be used. The pump must have a 3 gallon per minute output. Hoses should be jacketed for prevention of moisture contamination. Hoses should have a ¾” ID and tip size should be a minimum size 0.027 orifice. Do not use with hoses that have been used to spray acrylic coatings.

Apply in a single coat at 1.5 gallons per 100 sq. ft. to yield approximately 23 dry mils.

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