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!

Interior vs. Exterior Gelcoat

Brushable gelGelcoat is a big part of our business here at FGCI. When looking at gelcoat, there is a wealth of options to choose from. The most obvious first choice is the color of the gelcoat; we have a vast array of over 25 stock colors with the ability to color match to a sample you provide. Once you have the color figured out, comes whether you want to brush the gelcoat or spray it, as we have the ability to do either. Lastly, however, is the option many people have a question about; interior or exterior. Let’s look at both options so you know which you will want for your job.

Exterior Gelcoat is our tried and true standard. If our gelcoat doesn’t specify interior or exterior, then the answer is automatically exterior gelcoat. It doesn’t mean that the gelcoat is only good for external use, or the outside of a boat, it means, simply that it does NOT have wax or Sanding Aid mixed in. This means that the lack of Sanding Aid will result in a tacky finish. If you want to avoid the tacky finish, you will want to add something like Sanding Aid, Patch Booster or Duratec to the mixture. This is mainly used as your primary coat or coats as you do not have to sand between coats, given you don’t wait too long.

Interior Gelcoat doesn’t mean the gelcoat can only be applied inside, it means it has Sanding Aid or Wax mixed in. Interior Gelcoat is used as a final coat, due to the Sanding Aid allowing it to dry tack-free, it will give a nice finish. You will not want to add Duratec or Sanding Aid to this product. If you use this product as your primary coat and look to add another coat, you will need to sand it first.

Now that you know which product you need, you can buy your gelcoat with confidence. And as always, remember that we are here to help with any questions you have!

Tech Blog – 5 tips on Thinning Gelcoat

maxresdefaultWhen it comes to applying gelcoat, you really only have two kinds of methods; you can brush our brushable gelcoat, or you can use our standard gelcoat and spray it. Most go with spraying the gelcoat to give you the best finish. When spraying gelcoat, you will need a spray gun with a 3.0 tip or larger. If you don’t have a tip that large, most people generally thin the gelcoat. Everyone asks what you use to thin gelcoat, and everyone has an answer. Let me start by saying we don’t recommend thinning gelcoat if you can avoid it. Our techs liken it to chicken soup; the more water you add to it, the less like chicken soup it will be.

  1. Do NOT use Acetone. I have heard people recommend this, but it can cause all kinds of problems for gelcoat from running to fish-eyes to a yellowing of the colors.
  2. We recommend Patch Booster. Patch booster is an additive that will thin out your gelcoat while preventing running. The product will not affect colors like styrene or acetone and is added up to 25 percent by volume to your gelcoat (one quart per gallon). You will want to catalyze the gelcoat at 2% when you add this additive.
  3. We also recommend Duratec High-Gloss additive. This product has the added benefit of giving you a glossy shine without having to sand and buff at the end. The product also thins the gelcoat and will not affect the colors like styrene and acetone will. It can be used up to 50 percent by volume. If there is one tip we could offer, it would be to wait 24 hours before buffing when using this product. Buffing will give you a new-car shine. You will want to make sure you catalyze this product at 2%.
  4. We do not recommend Styrene for one main reason; it can affect colors. Styrene, when added up to 20% will thin your gelcoat but does often cause the gelcoat to yellow and any more than 20 percent will cause fish-eye.
  5. Both the Patch Booster and the Duratec affect your catalyst rate, so make sure you catalize properly before spraying and be sure to clean your gun carefully after each use (for that, you CAN use Acetone).