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Cold Weather and Fiberglassing

Cold Weather And Fiberglassing

The temperature is below 50 degrees and I need to do a fiberglass job. How do I do it successfully?

Tips for Fiberglassing When It’s Cold:

  • Check the weather forecast. Don’t begin your project if it is going to be damp and rainy.
    • Dampness will slow cure times and may cause epoxy to have amine blush.
  • Check the temperature. If it is below 55 degrees, you may run into curing problems.
  • To generate more heat, use a higher percentage of catalyst to resin.
    • Up to 2% for Polyester(20cc per Quart), 3% for Vinylester(30cc per Quart).
    • Use a Fast Cure Hardener if using Epoxy.
  • If outside tenting will help retain heat for your project.
  • If outside try to not fiberglass after 2-3pm because the sun is setting and you will lose heat.
  • The resin and material to be fiberglassed should be at a 70 degree room temperature.
    • Items for warming resin and surfaces: Water bath, heat gun, heaters, heat lamp, etc,.
    • DO NOT use a heat source that uses an open flame.
    • A heat source under your project will help warm more efficiently as heat rises.
  • Resin may thicken in cold weather.
    • Thicker resin requires extra effort to wet out the glass.
    • More resin than normal might be used due to its thickness.
  • Heat should be maintained for several hours after application.
  • Epoxy resin needs heat over a longer period of time to cure effectively.
    • Heat would need to be maintained over a period of days, rather than hours.

Fiberglass resins need heat to cure. Once the temperatures go below 60 degrees an alternate heat source needs to be used to make sure resin cures fully.  The type of resin used will determine the amount of time the heat would need to be maintained.  One of the best rules of thumb is to make sure all the materials that will be fiberglassed or used to fiberglass are at a temperature of 70 or over.  It is possible to fiberglass in colder weather, but you must take the correct steps to make sure your project is successful.

This Post Has 2 Comments
  1. Interesting But I have been using slow cure resin thickened for patching holes and low spots in 47 degree weather with no problem just takes longer to cure! Reason and hardeners are chemical reactive not mechanical, Right ? Or Wrong?

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