Besides mix ratio, temperature is one of the key reasons epoxy projects turn out successfully – or not. And it’s not just the temperature of the epoxy that matters – it’s also the temperature of the surface you’re pouring it onto and the ambient temperature of your work room.
When you mix the resin and hardener components, a reaction occurs that generates heat. Just how much heat and when it’s generated depend on the type of epoxy, the hardener speed, the volume that’s mixed, and the temperature. For example, a larger volume with fast hardener will heat up faster and get hotter than a small volume with fast hardener.
Above: TotalBoat epoxy river surfboards, by @rusted.indigo
Any excess heat in the room or on the surface will affect the working time and cure time, and can also affect the physical properties and performance, making the epoxy weak, brittle, or yellow if it gets too warm during the cure cycle.
How Warmer Temperatures Affect Resin
The best temperature range for working with epoxy is approximately 65°F-80°F, depending on the type you’re using. This temperature range applies to your work area, the resin and hardener components, and the application surface. In temperatures above 85°F, the mixed material will exotherm (heat up) much faster, giving you less time to mix and pour before it starts to set up. Not only is the working time reduced – the cure time is also notably shorter.
How to Make the Working Time Longer for Epoxy
- Use a slow speed hardener, if there’s one available for the system you’re using.
- To maintain the recommended temperature and control the humidity level, use air conditioning to cool the room.
- Before dispensing, keep the resin and hardener components cool by temporarily placing the closed containers in a cool-water bath.
- To help the heat dissipate, mix the resin and hardener components in a wider container that creates more surface area. Or mix the components thoroughly in a smaller container, then pour into a larger container before applying.
Why High Humidity is Bad for Epoxy Resin
You’ll get the best results if the humidity level is below 85%. Higher humidity means more moisture in the air, which can make the finish cure cloudy. It can also potentially make amine blush form on the surface of a non-blushing epoxy.
The really bad news is that if there is excess humidity, you won’t see these problems until after the epoxy has cured. So it’s a good idea to keep an eye on the temperature and humidity levels throughout the process.
How to Get the Best Results Curing Epoxy in Hot Weather
During the entire curing process, it’s important to keep the room temperature and humidity levels stable. The temperature shouldn’t exceed 85°F and ideally, the humidity should be between 50-60%. But always check the specified temperatures for the product you’re using, for best results.
- Use air conditioning to keep the room in the recommended temperature and humidity range. Be careful not to cool the room down too much or you’ll make the cure time longer.
- If using air conditioning or fans to cool the room, take care not to generate too much of a breeze to prevent dust from settling on the surface.
- To maintain the temperature in the room, keep windows and doors closed.
If you have any questions at all about working with our products in warmer temperature conditions, call our friendly TotalBoat Tech Support Team at 1-800-497-0010 for answers. For related topics, here’s more info on achieving best results in cold weather and adding UV protection to outdoor projects.
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