Epoxy resin is well known for its durable, solid structure in a variety of projects. From home flooring and furniture to small jewelry and other works of art, epoxy adds a firm coating to protect and enhance various types of material. Because epoxy is designed to form a strong bond and solid layer, it can be frustrating to discover bendy, rubbery, or even soft resin. This may lead you to ask the question, “Why is my resin soft?”
The most common reason that epoxy resin is bendy, rubbery, or soft is that it had an insufficient curing time. Other reasons for soft resin include inaccurate measuring, poor mixing, low-quality epoxy, thin pouring, and moisture in the epoxy.
To solve the issue of why your epoxy resin is flexible, it’s important to understand what caused the resin to improperly cure. In this article, we’ll explain why your epoxy resin may be soft and how to prevent this from occurring in the future.
Why is My Epoxy Resin Soft?
There are a number of issues that may occur during the preparation, pour, and cure of epoxy. One such scenario that many epoxy-users must deal with is epoxy that remains soft. Whether you mixed the resin improperly or the epoxy failed to cure long enough, there are several reasons for the epoxy to become flexible.
Generally, the reason for soft epoxy is a short curing time, as well as improper ratios of resin and hardener, not thoroughly mixing, pouring too thin, and using epoxy that retains moisture. Low-quality resin can also affect the epoxy’s ability to cure properly.
If any of these issues occur during the mixing or curing process, the epoxy will likely remain soft and bendy. While this may not appear to be a major issue, there are several reasons why epoxy must become solid in order to be useable. Not only is soft epoxy less attractive, but it is not as functional as epoxy that properly cures.
To avoid soft and flexible epoxy in the future, it’s important to understand what causes the epoxy to become rubbery. Below, we’ll take a closer look at why epoxy resin doesn’t harden properly.
Short Curing Time
One of the main reasons for epoxy being soft is that it did not cure long enough. Generally, the epoxy resin must cure for 72 hours before you may move or sand the project. In some cases, the epoxy may be dry by 24 hours, but it still needs to cure for 72 hours to ensure it cures properly.
There are a couple of factors that can affect epoxy’s ability to fully cure. These factors include the temperature of the workshop and the brand of epoxy you’re using. When the temperature outside is too cold, the epoxy will take longer to cure. Additionally, if the epoxy you’re using is cold to the touch, it may not harden properly after application.
The brand of epoxy you’re using also influences the epoxy’s curing time. While most epoxies require 24 to 72 hours to cure, certain brands may require longer curing times. Moreover, some brands need a specific temperature in order to fully dry. Before applying the epoxy to your projects, always thoroughly read the product’s instructions to ensure your workspace allows for a proper curing time.
Inaccurate Measuring
Epoxy resin is made up of two components: a base resin and a hardener. Measuring the correct ratio of these two ingredients is essential for promoting a solid cure. Failing to properly measure these two parts will result in bendy, rubbery, soft, or even sticky epoxy resin.
Before mixing the resin with the hardener, be sure to read the epoxy’s mixing instructions. While most epoxies require a 1:1 mixing ratio, others require a 2:1 ratio. Additionally, some epoxy ratios are measured by weight, while others are measured by volume.
Improper Mixing
Once you measure the correct amounts of resin and hardener, the next step is mixing the two parts together. Mixing the ingredients is a somewhat crucial process, as it creates a chemical reaction between the hardener and resin. When the epoxy is improperly mixed, it may become solid but never fully cure at the final stage.
A common mistake that many epoxy users make is failing to stir the epoxy long enough. While most epoxies take 2 to 3 minutes to mix by hand, large quantities of resin may take up to 5 minutes or longer. When pouring the epoxy on your project, avoid scraping the sides of the container, as the sides are most likely to be mixed poorly.
Thin Pour
Pouring too thin is another issue that can cause the epoxy to remain bendy or soft. While it is indeed possible to pour thin layers of epoxy, it is important to use a resin designed for that specific depth. Using epoxies designed for thicker levels will only result in flexible epoxy.
If you happened to pour the epoxy too thin on your project, you may consider adding a second layer once the epoxy cures. Keep in mind that this can be difficult if the first layer of epoxy never becomes fully dry. To ensure a proper bond between the surface and epoxy, you’ll need to sand down the entire epoxy piece. Always allow the epoxy to cure for 72 hours before sanding it, even if the epoxy remains bendy or rubbery. If your epoxy is sticky even after curing, you may need to scrap the sticky spots off before adding the second layer of epoxy finish.
Epoxy Resin Retaining Moisture
When moisture enters your epoxy project, the resin is likely to become soft and rubbery. Whether the moisture is in the container or on the surface, a resin that retains moisture will prevent the piece from curing properly.
Oftentimes, epoxy resins retain moisture after adding large doses of liquid pigment. Similarly, applying the epoxy in a damp location may cause the resin to retain moisture. You may also expect moisture in your project if you clean the mold with water or alcohol but don’t allow it to dry.
Low-Quality Epoxy Resin
A final reason for the epoxy resin to remain bendy, rubbery, or soft is that the brand is low-quality. Many low-quality brands fail to get hot enough to have a proper exothermic reaction during the application process. As a result, the resin may pour too thin and never fully harden.
Before you begin working with epoxy, always make sure to select high-quality epoxies from reputable brands. By using a high-grade epoxy resin and hardener, you can prevent soft epoxy from occurring in your projects.
