11/28/2023 0 Comments Jason killmer sanding blocks![]() some people will try to combat this with a high build primer or spray poly, which is NOT the answer to shrinkage. When the resin loses solvent and shrinks it will pull the topcoats (gel coat, primers, paint) down with it, magnifying the effect. Shrinking is natural in our industry, every liquid product WILL shrink, the question is to what extent. this happens because as the fiberglass (specifically the resin) dries it loses mass like any other product. When fiberglass parts shrink, they often form new waves in the panel or you may even see the strands or weave of the fiberglass showing back through in the paint. These solvents are the reason that some fiberglass parts shrink so much. when these parts are made there are solvents in the fiberlgass, even after its " cured". this liquid product like many liquid products contains high amounts of solvent. When fiberglass parts are made they use a liquid resin, activated by a liquid hardener (peroxide mainly). the more you bake the less likely you are to have shrinkage later. bake it for an hour, let it cool naturally, bake it another hour, repeat as many times as you like. ![]() its always a good idea to go the extra mile. most often you will bake the panel at a surface temp of 150-160 degrees F for at least one hour. ![]() As we talk about quite often, the Infared light will actually heat the panel from the bottom-up vs whereas a booth bake will be from the outside in. we have found that the Infared Light works much more effectively for this process. Most fiberglass hood and body manufactures recommend baking the parts in the booth in a bake cycle for at least 1 hour. Step 1 in Fiberglass parts Preparation is a good long bake. The question is WHY? Baking Fiberglass Parts Some shops may struggle with fiberglass hoods/bodies shrinking back to the point you can actually see the fiberglass weave pattern in the paint a few months/year later, waves appearing that were never there before, or even blisters.
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