How Does Humidity Affect Curing Epoxy?

by Roderick Kabel

When we see epoxy blushing or excessive bubbles in cured epoxy, some of the first questions we ask are: What was the air temperature? Was it humid during your project cure? What was the humidity level?

Blushing is a sticky, oily, or waxy appearance on the surface layer of cured epoxy caused by added moisture from humidity. Changing temperatures can also cause similar issues with condensation, so keeping the temperature level consistent throughout the entire curing process is also an important factor.

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Epoxy needs to be kept in a very specific environment throughout the curing process to achieve a flawless pour. Understanding humidity is key to getting your epoxy mixture to cure. Humidity is the amount of water vapor in the air at any given time. So, how can issues with humidity be avoided.

Epoxies will cure in the presence of moisture brought on by humidity, but in the instance of using table top or the casting epoxy, moisture from humidity will make epoxy cure cloudy and lose clarity (blushing). In addition, the moisture in the air can also cause the epoxy to foam or cause an extreme reaction and cure too quickly.

Suggested humidity levels should be below 85%, ideally between 50-60%, throughout the full cure cycle, and the suggested temperature range for curing epoxy is between 70-80F. It’s important to keep in those ranges throughout the pour and cure. Don’t think once you leave the room you can turn up the air or open a window, because it will hurt your project.

Typically, we don’t see moisture problems until the epoxy cures, so it’s crucial to keep track of your levels as you pour and start the curing process to achieve a clear finish.

So, what can be done to prevent curing issues in a hot or humid climate? Here are some tips:

  •  Be sure to have a properly working A/C system blowing into the workplace to help control humidity.
  • Always have fans blowing near your project throughout the cure.
  • Avoid bringing in outside air as much as possible by keeping doors and windows closed
  • To reduce humidity, you can cool the room down. However, that could lead to a longer cure time.

High summer temperatures most often bring with them high humidity, and keeping the temperature and humidity level consistent throughout an entire pour and cure can make a huge difference in the final product.

Comments (1)

  • Je' Czaja-Mordon
    Mar 31, 2022, 11:28 am

    Thank you for this. I live in FL and had no trouble until this summer-high temps extreme humidity 80 percent plus. The AC struggles with this much wet air. Last few projects weird and sticky but I’m mixing and measuring carefully. So bad I noticed glue and paint weren’t drying. Got a room dehumidifier and it’s sucking 2cups of water every day out of the air. I shall try again.

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