Tech Question: “Can I apply resin to foam?”

foam-blockMany of our customers look to make sculptures out of fiberglass and resin. Foam is a common material as it’s easy to carve and sand to your desired shape. But, can you put Polyester resin on the top of it? It’s a question we get asked constantly.

Your first step needs to be finding out what kind of foam it is. Certain types of foam have different temperature variations. Polyurethane foam, like the kinds we sell in 4’ x 8’ sheets offer different temperature variations from things like Polystyrene. Once you figure out which foam you have, you can figure out what you need to do.

With Polyurethane foam, it will easily withstand Polyester or Epoxy resin applied to the top of it without having to do anything special. We recommend scuffing the surface with some sandpaper to get the best bond, but once the standard surface prep is done, you can apply your gelcoat, resin or epoxy.Polyurethane foam

With Polystyrene or Styrofoam, you can’t directly apply Polyester or Epoxy directly to Styrofoam, as it will melt the foam. Fortunately, we have a couple of products you can use to still make it work. The first product is an FGCI product called Styrocoat that uses a standard epoxy activator and will provide a protective shell over the Styrofoam. The other product is made by Duratec and is called Styro-Shield. Styro-Shield is a Polyester-based product that uses MEK-P and will provide a protective coating once hard.

So, no matter what kind of foam you use, we have a way to make your fiberglass mold or fiberglass-based product. Don’t forget that if you have questions, we are here to help! Give us a call at 1-800-272-7890, or e-mail us or contact us through Facebook or Twitter!

Tech-Tip: Coring Material

Coring Material is a very important step in your fiberglass project. Coring is what takes a sheet of fiberglass and turns it into a solid panel, for decks, boats, and so much more. Coring material can give the sheet flexibility, rigidity or even insulation (which is important when making a cooler). We carry several different kinds that offer pros and cons. It’s important to find the material that works best for you.

Honeycomb –


  • PVC honeycomb with a fiber covering.
  • Very flexible and light-weight.
  • Does not rot and has great bonding properties.
  • 5lb density sheet

Diab –


  • Offers several densities (3, 4 and 5lb denisty) for different jobs.
  • Much more rigid than plain polyurethane foam
  • Tan color (used to be multi-colored).

Polyurethane foam –

Polyurethane foam

  • Great in-expensive coring
  • Light-weight
  • Does soak up resin and has a good bond.
  • Does compress if you aren’t using the proper density.
  • Greatest R-Value (insulation) of any of our options.
  • Sold in 2lb and offered in 4lb density

Kay-Cel –


  • 25lb density sheet with 18 oz Woven Roving in the middle
  • The most dense, heavy material we have
  • Perfect for transoms or pieces with a heavy load

Balsa-Core –


  • Seal-coated wood to reduce resin consumption, keeping the weight down and increasing the bond.
  • Very lightweight, and inexpensive solution.
  • Does eventually rot without proper sealing.
  • Very good compression tolerance