Epoxy Resin not Hardening?

Like most artists and crafters testing the waters with epoxy resin, you've probably faced a typical problem that beginner resin enthusiasts have: after curing time, the resin is still sticky or gummy. Unfortunately, there are several reasons why your epoxy resin might not fully harden as expected. But no worries, we’ll discuss the most critical factors to consider when working with resin to ensure it sets properly, from mixing ratio to weather or room temperature and even recommended pigment ratios.

Mixing Resin and Hardener Ratio

When mixing resin (Part A) and hardener (Part B), a chemical reaction occurs, resulting in a crystalline solid finish. Therefore, the correct ratios of each component in the blend are critical to getting the expected outcome. 

When the epoxy resin starts to cure with an incorrect ratio in the mixture, it prevents the reaction from completing, and your project ends up with a surface that still feels tacky long after curing. Many describe the texture as feeling like the sticky side of tapes. The good news is this can be easily avoided by thoroughly following the manufacturer's mixing ratio.

Recommendations to avoid sticky resin:

1. Measure out your Resin and Hardener precisely by volume; otherwise, the chemical reaction between the two ingredients will not work correctly, leaving you with an incomplete cure. 
2. Follow the mixing ratio on the product’s label. For example, most Resins are 1:1 or 2:1 of Part A (resin) and Part B (hardener), usually measured by volume, but some resin brands suggest using weight instead. So, always check your product’s label first.
3. Thoroughly mixing is just as important as measuring. Mix for a minimum of 3 minutes or until no striations can be seen, and make sure to scrape down the sides and the bottom of your container to get everything in. Failing to do so will result in the resin not hardening as it should.

Now that you know the basics to ensure resin projects harden as expected, you’re probably wondering how weather, added pigments, and storage conditions might affect the curing process. Keep reading this article, and you’ll discover the ins and outs of working with resin and getting the best results possible.

Resin to Pigments Ratio

Pigment powders like micas, metallic pigments, and glitters are a great way to add color and special effects to your resin art projects. However, even though they are primarily inert and do not dissolve, they might accelerate the reaction time of some epoxy resins like the ones used for coatings and paintings, which cure faster. On top of that, in some cases, too much pigment powder can prevent the resin mixture from curing properly. 

A tiny bit of highly pigmented mineral powders like micas will go a long way when adding color and pearlescent effects to resin art projects like jewelry, resin coasters, or geode-inspired paintings. For epoxy resin river tables and larger resin casting projects, a more significant pigment load will be needed but still not a lot. Estimating how much pigment you need depends on the size of the project and the desired opacity and effects. You can learn more about this in our blog post linked here.

Resin to Pigment ratio recommendations:

1. The amount of pigment you use to color your resin will determine how translucent the final result will be. For example, the recommended mica powder to epoxy ratio in small projects is 1g of mica powder per 1oz of epoxy resin for a rich solid color. We always recommend starting by adding a tiny amount of pigment and continually adding more until you get the desired color and level of saturation.
2. A general rule of thumb for a vibrant, fully opaque result is using 1% to 3.5% pigment powder in the total amount of Epoxy Resin by weight. Of course, the greater the percentage of pigment you use, the more saturated the final result will be. 
3. Please keep in mind that adding more than 10% of any pigment or paint to your resin could affect the curing process.

Best temperature to work with Resin

Temperature is one of the most crucial factors to guarantee your epoxy resin cures properly. The best temperature for your resin and workspace is slightly warmer than standard room temperature: 75-85°F or 24-30°C. 

Also, epoxy resins won't harden properly when the temperature is too low, so some precautions must be taken during cold weather. Usually, if the temperature of your art-dedicated room is below 72°F/22°C, your resin may stay sticky for days or may not cure at all.

Below you’ll find some tips depending on the season of the year or weather conditions you live in.

Will epoxy cure in hot weather?

The short answer is yes, but the room temperature shouldn’t exceed 85°F or 30°C. For optimal results, working with 2 part epoxy resin in a warm, dry environment throughout the curing process is best. 

Although warm temperatures are preferred over cold, a hot and humid climate can cause issues, and excessive heat exposure can also affect curing resin.

For your convenience, here are 3 simple tips to help you beat the heat and ensure a successful summertime resin:

1. Keep your workspace, resin, and tools at standard room temperature: ideal conditions are 75°F/24°C - 85°F/30°C and should stay stable for the first 24 hours after the pour.
2. Ideal humidity is below 50%; however, you can work in up to 80% humidity conditions.
3. Recently cured resin should not be exposed to high temperatures or direct sunlight for long periods.

Will epoxy cure in cold weather?

As the temperature drops, epoxy resins become thicker and will not flow properly. In addition, it is much more challenging to measure and mix the epoxy resin and hardener in cold weather, leading to incomplete mixing and a greater risk of coating failure. Cold, thick epoxy also cause application and curing issues, such as an uneven appearance and air bubbles in the finished product.

Unless formulated explicitly for cold-weather use, most epoxies will never fully cure at temperatures below 50°F or 10°C. Therefore, to ensure the chemical reaction is off to a good start and promote optimal curing in winter:

1. Warm the resin and hardener at least to 70°F or 21°C with heat lamps or keep them in a heated environment before use. 
2. Keep the working area heated during the epoxy’s full cure time.
3. Since the ideal application temperature of each Epoxy Resin differs from brand to brand, we recommend checking the product label or contacting the manufacturer for specifics.

What is the best temperature to store epoxy resin?

Opened or unopened, store your Resin bottles in a dark spot, out of direct sunlight, and in an area where the temperature will stay stable at room temperature or just slightly below ( 70°F or 20°C ).

Conclusions

Following the manufacturer’s mixing ratios and maintaining the recommended humidity levels, room and resin temperature are the most critical factors in guaranteeing your Resin Art Projects harden appropriately. Also, it's important to know that warmer temperatures accelerate the chemical reaction while colder temperatures slow it down. Both will directly affect the epoxy's cure time and physical properties.

In the summertime, air conditioning is a great idea to help keep standard room temperature between 72°F/22°C and 85°F/30°C. However, if air conditioning is not an option and the temperature exceeds 85°F/30°C, try to work in the coolest part of your house in the early morning or later evening.

Unless your resin is formulated explicitly for cold-weather use, epoxies won’t fully cure at temperatures below 50°F or 10°C. Therefore, it is highly recommended to warm the resin and hardener at least to 70°F or 21°C with heat lamps or keep them in a heated environment before use. 

Be careful also when adding pigment powders to your resin art projects. To get the desired results without compromising your resin's hardening process, avoid adding more than 10% pigments to the total amount of resin by weight.

If you are interested in learning more about Epoxy Resin Safety, check this article to ensure you take proper care of your health when working with this medium. We also explain how to select the best epoxy resin for each type of project in this blog post. Check it out to master the Resin Art game in no time!

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