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).

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