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Hot Wire Foam Factory

Exterior Foam Coat

Exterior Foam Coat

Regular price $10.99 USD
Regular price $0.00 USD Sale price $10.99 USD
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16 in stock

Exterior Foam Coat

Rock hard coating for all your outdoor (and indoor) foam projects!

New improved formula! Extended working time of 1.5 - 3 hours. This stuff is super tough. It is not sandable. Has a rough stone feel when dry. It can be troweled smooth, or brushed to make a super rough finish. Can also be applied with a hopper gun.


  • Adheres to polystyrene foams
  • Forms a weather-resistant surface
  • Use above or below grade
  • Apply with a paintbrush, trowel or hopper gun
  • Paintable
  • Fireproof
  • Many decorative surface textures can be created
  • Soap and water clean-up
  • Add Boost fortifier if extra strength is desired. (will not work with Bounce)
  • Made in USA


Used For:

  • Coating Styrofoam, white beaded EPS, and extruded XPS foam
  • Adding strength, texture and a weather and fire-resistant surface
  • Theatrical and studio props and backdrops
  • Holiday props, like Halloween tombstones and yard props
  • Garden décor, like fake boulders and waterfalls



Thickness: 1/64" 1/16" 1/4"
3lbs: 36 sq ft 9 sq ft 2.25 sq ft
25lbs: 288 sq ft 72 sq ft 18 sq ft

MIXING: Settling may occur in shipping causing a gritty texture that does not stick well. Remix if there is separation in dry mixture. Remove or break up any clumps. Use when temperatures are between 40°F (4°C) and 100°F (38°C). Mix in a clean container with clean water. Use 1 part cool water per 3 parts of powder (for example, 1 cup of water per 3 cups of powder). Add water to powder and mix until Foam Coat turns to a smooth paste. Add more powder or water as needed for your application. A drier mix is stronger. If you add Boost, a wet mix is stronger. Do not over mix. You can add powdered or water base cement pigments while mixing in the wet ingredients.

APPLYING: If using extruded foam (ie Blueboard or Pinkboard) roughen surface with coarse sandpaper. Fill big cracks and holes by applying pasty mixture with a trowel. You may add more water until mixture is thin enough to apply with a paint brush, although thinning weakens coating. Can be applied with a standard spray hopper. Use thinned mixture to texture large areas. For best strength apply at least 1/4” (6mm) thick. Multiple coats may be applied. Try texturing surface before coating sets.

CURE TIME: Working time of 1.5-3 hours. Reaches 80% of its strength in 12-24 hours, depending on temperature and humidity. Fully cures in 3-5 days. Lightly fogging the surface on and off for 24 hours will increase strength.

FINISHING: Remove dust before painting or staining. This product goes on rough and is not sandable. Finish as the surface is setting up.

CLEAN-UP: Clean tools and brushes with clean soapy water before coating hardens. If you add Boost, don’t leave any residue as it will be impossible to clean after it dries.

WARNING: Avoid prolonged contact with skin. Wear dust, skin and eye protection. Use approved respirator when sanding. In case of eye contact, flush immediately with water, consult a physician. Wash hands with soap and water after use and before eating. Keep out of reach of children.



More Info:

1 Day 750 psi
7 Day 2500 psi
28 Day 3500 psi

1 Day 350 psi
7 Day 550 psi
28 Day 1250 psi

Flammability: Noncombustible and not explosive.
Auto-ignition Temperature: Not Applicable
Flash Points: Not Applicable

Click here for Exterior Foam Coat Mixing Details and User Tips

WARRANTY: HWFF Inc./dba Hot Wire Foam Factory warrants this product to be of merchantable quality when used or applied in accordance with the instructions herein. The product is not warranted as suitable for any purpose or use other than the general purpose for which it is intended. Liability under this warranty is limited to the replacement of its product (as purchased) found to be defective, or at the shipping companies’ option, to refund the purchase price. In the event of a claim under this warranty, notice must be given to The Hot Wire Foam Factory in writing. This limited warranty is issued and accepted in lieu of all other express warranties and expressly excludes liability for consequential damages. MSDS available.

⚠️ California Proposition 65 Warning: This product contains crystalline silica, a chemical known to the State of California to cause cancer, birth defects, and reproductive harm. While mixing the dry ingredients use a dust mask or respirator with an RPE of 20 or 40. For more information, go to or HWFF's information page: California Proposition 65.






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