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Understanding the Effect of Humidity on Epoxy

It's a must to keep epoxy in a well-managed environment during its curing process so you can achieve a perfect pour. And one way to get an ideal epoxy cure is by understanding the effect of humidity on epoxy (the amount of water vapour in the air).




But how can this gaseous state of water interfere with your resin art? Will epoxy cure in hot weather? Does humidity affect epoxy resin? These are all questions you need to consider before entering the process.


While it might seem like a great idea to cure your resin in warmer temperatures, too much moisture in the air can affect your project's final result. If you're not careful, you might end up with a cloudy finish or an oily-looking surface layer. This loss of clarity usually occurs either in the pouring or during the curing phase itself. For this reason, you must remember to control the standard temperature and humidity levels during the curing process. Using air conditioning (not evaporative cooling as it produces moisture) is one way you can regulate humidity, but you can also run a dehumidifier a day ahead, if your work area is in a very humid place, as this may assist.


In this article, the team at Just Resin explore the perfect temperature for resin to cure and more.


How Does Humidity Affect Epoxy Resin?


So, how does humidity affect epoxy? And how will you know it when it happens?


Under typical conditions, you won't see excess moisture issues until the epoxy cures. That's why it's crucial to keep your levels under control as you start pouring and commence the curing process to achieve a clear finish the first time around.


One sign of excessive humidity on your cured epoxy is when its surface layer is 'blushing.' This means that it has an oily, sticky, or waxy appearance, which can be an aftereffect of changing temperatures and high humidity. To avoid similar condensation issues, you must keep the consistency of the temperature level throughout the epoxy curing process.

The moisture in the air can lead to foaming of the epoxy or an exothermic reaction wherein the curing process will finish too quickly.


Will epoxy still cure in hot weather? The answer is yes. In fact, warmer temperatures speed up the curing process, but just like anything else, too much of a good thing can lead to negative consequences. That's the case in curing epoxy as well.


To help, note these six things that contribute to the temperature of epoxy:

  1. The ambient temperature or the climate of your work area, 22-25 degrees Celsius is ideal.

  2. The temperature of the surface where you applied epoxy (another part of the ambient temperature).

  3. The exothermic heat, or the heat generated by curing epoxy.

  4. Leaving mixed Resin in a confined space (eg cup, jug) will accelerate curing and could encounter aggressive exothermic reaction.

  5. Incorrect ratio of Part A (Resin) to Part B (Hardener) - measuring is to be precise.

  6. More than 10% ink/pigment/acrylic paint to Resin ratio used. *Making note that some acrylic paints or pigment additives may not be compatible and may accelerate the curing process.


The Cure Stages of Epoxy


When you mix the Part A Resin with Part B Hardener, a chemical reaction begins, transforming the mixture of liquid ingredients into a solid matter. This period is what we call the cure time. While the epoxy cures, it comes from its liquid state to a gel state halfway through the process. After that, it reaches its solid form.


Here's a quick breakdown of the cure stages that the epoxy goes through:


1. Open Time (Liquid)


You might also hear this referred to as the ‘working’ or ‘gel’ time. This phase after mixing is when you can work with the epoxy mixture as it remains a liquid. To ensure a dependable bond, you must use this time to finish your project.


2. Initial Cure Phase (Gel)


The epoxy is no longer workable during this stage as it has already transitioned into its initial cure phase. Here is where the material starts to 'kick-off' and begins heat up as its reaction to cure. It turns into a gel state and becomes non-sticky halfway through the process.


The epoxy might still be as sticky as masking tape at this part of the curing process. Still, this surface can be bonded to or recoated without surface preparation. It's when the two layers form a primary or chemical bond.


3. Final Cure Phase (Solid)


As the name suggests, the solid stage is the last phase in the epoxy curing process. It's where you can dry sand the epoxy resin as it has cured into a solid state.


At this time as the epoxy has reached its utmost strength. However, applying a new layer of epoxy will no longer form a primary bond on this material. If you must do so, first clean, dry, and you can lightly sand the surface so you can attain a stable secondary or mechanical bond to it.


This new mixture will then carry on the curing process for several days and can last up to two weeks, conforming to its inert, solid form.


How to Set the Right Temperature for Resin to Cure


Whether your epoxy resin art is a home project or a small business production, it's crucial to achieve the right temperature. Comply with the standard heating instructions for both the environment and the materials. Do this, and you're sure to have a successful application. Otherwise, your output might be subject to a cloudy finish, dimply, soft or wet spots, and troublesome excessive air bubbles.


You don't want such an unsatisfactory finished product after exerting all that investment, time, and effort. To avoid that, here are instructions on how you can set the proper temperature for the resin to cure perfectly.


Important: These instructions are not mere tips or recommendations. Instead, these are requirements in preventing epoxy curing issues.


Setting the temperature for resin to cure:


● Keep the room and product at least 22° C before using the epoxy until during the curing process. (72 hours)

● Immediately bring it inside when receiving the epoxy outdoors with weather colder than 22° C. Let it acclimate to the right temperature before mixing.

● We recommend using small space heaters with thermostats if you wish to warm up your room quickly.

● Not all thermostats are 100% accurate, but you can still achieve the correct temperature by setting it a few degrees warmer.


Maximum temperature for resin to cure:


● The closer you keep the temperature to 25° C, the better.

● In case of issues maintaining a stable climate, going over instead of lower than the standard temperature is better.

● The standard is no more than 32° but should never go any lower than 15°.

● Warmer temperatures promote a quicker reaction on the epoxy, hence faster results, shorter mixing times, and faster cure times.


Settling the humidity to minimise the adverse affect on epoxy resin


● Prepare the environment and the epoxy as dry as possible.

● Maintain the humidity level below 80%.

● Ensure no excess dew enters the mixture to avoid inconsistent results in storage and working procedures.

● Keep any wetness away from the epoxy while mixing to ensure a smooth finish.



Finish Resin Art Projects Like a Pro (Even if You're Just a Beginner)


As long as you're a resin art lover, it doesn't matter if you're a new hobbyist or a beginner jumping into resin art. Our team is dedicated to helping you get access to quality resin art supplies and informational guides so that you can finish your projects like a pro.


Before you unbox your resin art supplies, here are a few more tips for you:

● Prepare a working air conditioning system (not evaporative cooling) directly in your workplace to help manage the ambient temperature. ● Prepare a working dehumidifier to assist with controlling the humidity in the workspace.

● You may cool the room down to minimize humidity, but it might lead to a longer cure time. Adjust as needed.

● Be mindful of the climate in your workplace. Too much of a hot summer can bring undesirable levels of humidity.


Aside from keeping the variables as constant as possible, having the proper materials and ingredients can significantly impact your epoxy resin project. We can help you with both here at Just Resin, your ultimate go-to for resin supplies and guides. For more information on epoxy resin and more, please do not hesitate to contact our friendly team at Just Resin today.

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