A glossy finish epoxy bar top

Epoxy is often applied to materials that don't fare well with water contact or even light moisture; but what about the epoxy itself—how does water affect it?

Fully cured epoxy is waterproof

Epoxy is an excellent sealant. Once it has bonded and finished the curing process, it can effectively prevent the passage of almost any substance or material, including water and humid air; for example, epoxy is often used in flooring, as well as for the shower walls of a full bathroom.

Epoxy shower walls in a domestic bathroom

Epoxy in its uncured or resin form is not waterproof.

You’ll want to avoid moisture when working with your epoxy prior to curing. If water gets onto epoxy resin before it has finished curing, it will likely seep into the mixture and cause various problems. It may reach the substrate that your epoxy is bonding to and cause damage there. It could also prevent the chemical bond from fully forming, resulting in a structural weakness that would leave the epoxy fragile.

Where they are present, liquids also tend to disrupt the heat dispersion of the epoxy curing process, leading to partial curing with soft spots in those places.

It's a problem that's easy to avoid once you're aware.

Humidity can ruin the visual results of the curing process

When unpigmented epoxy is curing normally, it will appear clear after the process has completed, similar to glass. However, if you attempt an epoxy project in a location with too much relative humidity, moisture from the air may condensate lightly within the epoxy or adjacent surfaces during the mixing, pouring, and curing steps. The typical result of this situation is a murky finish that lacks the desired transparency of a proper epoxy finish. For optimal results, keep your temperatures regulated to epoxy resin's ideal curing range of 70℉ to 80℉, and keep the humidity levels of your space at 60% or below.

How to avoid the humidity problem

If you’ve no choice but to work within in a humid environment, there are steps you can take to prevent this from ruining your epoxy project.

  1. Maintain the temperature at the appropriate range of 70°F to 80°F. This is the range in which epoxy can cure properly. We at UltraClear Epoxy try to keep our work spaces at a tight 75°F, but anywhere within that range is suitable.
  2. Keep the humidity to 60% or less. Consider using a dehumidifier to accomplish this. Many dehumidifiers allow you to set the desired humidity level. If you’re working in an enclosed space (which you should, even if you have to construct something simple and temporary), you’ll be able to control the humidity with machine like this. Keeping your epoxy work space to about 50% humidity will allow the project to cure without concern for condensation, as long as the temperature of the space itself doesn’t go beyond the safe curing range (70°F to 80°F).

An epoxy penny countertop with a sink

For peace of mind, try our UltraClear Epoxy

All of the information in our articles applies to epoxy that meets certain industry quality standards. We at UltraClear Epoxy stand by our products; whether your project requires a traditional table top epoxy or something specialized like our deep pour epoxy, you can rest assured knowing you'll receive top quality waterproof epoxy that meets our rigorous standards.

Have questions? Want assistance? Contact us!

If you have questions that aren't answered in this article, or if you would like help with planning an epoxy project, you can contact us via phone or email. You can also text chat online with one of our experts by clicking the help button at the bottom right of your screen.

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