10 Things that Can Go Wrong with Epoxy Resin


fire on epoxy table

Dreaming up your next epoxy resin project can be incredibly exciting. There are endless possibilities for creators choosing to work with this substance; all it takes is a little know-how. However, if you are new to working with epoxy resin, you may find yourself experiencing one of these common mistakes.

Some of the most common things that can go wrong with epoxy resin include surface imperfections, the formation of bubbles, uncured or unhardened resin, cracks in the resin, an unlevel pour, discoloration, not functioning as an adhesive, loss of glossy appearance, and a bulging effect.

Fortunately, epoxy resin can be a somewhat forgiving product to work with if you take active steps to address any issues as they arise. Of course, if you were to continue pouring thin layers of epoxy over the troublesome layers, you may be wasting your time and effort. But, if you address the issues quickly, then you will likely find that the problems are not too difficult to avoid or resolve. Let’s take a closer look at these issues.

1. Surface Imperfections

If you are working with epoxy resin, then you know that this substance has the ability to quickly attract any floating particles in your workshop. This is particularly frustrating when working with wood- knowing that you will need to maintain a clean environment free from floating sawdust and other particles that may end up on the surface.

To avoid surface imperfections with epoxy resin be sure to maintain a clean work environment. Any free-floating particles can end up on the surface of your fresh epoxy resin pour and become one with the surface. This also includes preventing bugs from entering into your workspace, as they can easily become stuck and embedded into the epoxy resin.

To resolve surface imperfections with epoxy resin you can likely sand down the surface where the imperfection rests, remove the imperfection (such as a particle of dust, hair, or bug), and pour a new, thin layer over the surface and allow it to harden.

2. Formation of Bubbles

The formation of bubbles is another incredibly common problem when working with epoxy resin. This is typically due to mixture and heat variations in the resin/hardening agent combination. The bubbles are generally formed as air pockets attempt to leave the hardening resin during the catalyzation process.

To avoid the formation of bubbles with epoxy resin be sure to pour in multiple, thin layers that adhere to the suggestions of the product description. Pouring in layers that are too thick can increase the risk of bubble formation (among other issues) with epoxy resin.

To resolve the formation of bubbles with epoxy resin you can use a heat gun (blow torch) lightly on the surface of the hardening epoxy resin. You will want to do this as the bubbles are forming as this method won’t work once the bubbles are already set into the hardened surface. Of course, you will want to do this quickly and with precision so as to avoid overheating the epoxy resin.

If the epoxy resin has already completely hardened and you are just now noticing bubbles under the surface, your options are to sand down to the bubbles and re-pour, or you can embrace the bubbles and move onto the next stage of your project.

3. Uncured Resin

Working with epoxy resin can be a slow and somewhat painful process if you are over-eager to see the finished results. You cannot rush the process when working with epoxy resin. Instead, you will need to follow the science behind the descriptions (cure time, temperature range, pour depth, mixture ratios, etc.) of the specific products that you are using. 

If you notice a sticky formation of film on top of the hardened epoxy when the rest appears to have cured, this is typically the result of environmental factors.

To avoid the sticky formation of uncured resin on the surface be sure to follow the recommended product descriptions in forming a controlled environment to pour your epoxy resin. A failure of your epoxy resin to completely harden typically is a result of user error anywhere from the mixing ratios stage to the temperature control. To avoid this, follow all of the product guidelines.

To resolve the sticky formation of uncured resin on the surface, you may be able to simply wipe the filmy layer off with a damp (but not soaked) cloth. If you are still having issues, you can try sanding down the surface, but you may need some pretty coarse sandpaper to make this work.

4. Unhardened Resin

If you have noticed that the resin is not just sticky on the surface but seems to be unhardened throughout the entire layer you have poured, this is likely a result of failing to wait for the adequate cure time or it could be the result of failures to adhere to the other recommended product details (as mentioned above).

To avoid unhardened resin be sure to adhere to the product recommendations on the specific epoxy resin and hardening agent you are using. For example, pouring with a deep pour epoxy resin will have different product recommendations to put in place during use than table top epoxy resin. Be sure to use an appropriate mixing ratio (and stir for an adequate time), as this is often the start of the problem that is to come.

To resolve unhardened resin will depend on how unhardened the product is. If the product was not able to experience the desired exothermic reaction, then it was likely in too cold of an environment. You can attempt to apply heat, but you may want to test this on a small portion of the project before moving on. Otherwise, you can choose to remove the unhardened resin by completely sanding it down and starting over, paying more attention to what you are doing, and not trying to skip any steps.

5. Cracks in Resin

Cracks typically form in epoxy resin during the hardening process if the catalyzation is over-amplified. For example, if the epoxy resin becomes too hot during the exothermic reaction, then cracks are likely to form as the resin (and its container) is unable to maintain product integrity. You may also experience smoke or fire in this type of situation.

To avoid cracks in epoxy resin be sure to use the recommended product pour depth and temperature storage. Pouring too thick of layers can increase the likelihood of cracks as the exothermic reaction would grow too robust for the product to be able to handle. Too much applied heat (be it from being poured in too hot of a workshop or from manually applied heat being added) will also increase the risk of cracks, so be sure to avoid this.

To resolve cracks in epoxy resin will depend on the severity of the crack. If your product has completely split in half, it may be best to attempt to sand it down and apply an appropriate adhesive. If you notice just a small crack in the surface, you might have better luck sanding it to the crack and beginning the pouring process all over again- being sure to do so under the appropriate conditions this time.

6. Unlevel Resin Pour

If you notice that the epoxy resin begins to run in one direction or the other in your contained pour, then the surface of the product (or the entire product) may be unlevel, to begin with. This can result in an uneven distribution of the resin as it hardens.

To avoid an unlevel resin pour is quite simple: be sure to level the surface of your project before you pour. You will want to use a small level to ensure that each end and the middle of your project is level, and test it in multiple directions. If your product is unlevel, then you will need to raise it until it is even on all edges of the project.

To resolve an unlevel resin pour you can sand the hardened epoxy resin down until the surface is level again. Then, once you have ensured a level surface, you can begin the pouring process again.

7. Discoloration

Discoloration of epoxy resin can take place in two main ways: yellowing of the hardened epoxy resin or redding of the hardening agent in its container. 

Yellowing of the hardened epoxy resin typically is a result of UV exposure. Since epoxy resin is not UV resistant, the yellowing is a result of the epoxy resin’s inability to protect itself from the effects of the sun. 

Redding of the hardening agent, alternatively, is typically something that happens when the product has sat on the shelf past its suggested shelf-life.

To avoid discoloration of epoxy resin be sure to use products that are within their recommended shelf-life and have not expired. Then, once you have finalized your project, you may add a UV resistant topcoat to the surface to protect the project from discoloration.

To resolve discolored epoxy resin you may have to sand down the entire project and re-pour from the beginning. Unfortunately, discoloration is a more difficult problem to encounter and is often the result of prolonged UV exposure. Keep your projects out of the sun to avoid this from the start.

8. Epoxy Resin is Not Functioning as an Adhesive

If you are working on a river table or otherwise using epoxy resin as an adhesive or bonding agent, and you notice that the project is not sticking to the epoxy resin, this could be a result of many factors. Primarily, you can expect that the epoxy resin is seeping into the porous surface that you are attempting to adhere to rather than remaining on the surface and capable of acting as a bonding agent.

To avoid epoxy resin not functioning as an adhesive you may want to apply a thin coating to the surface that you are attempting to use the epoxy resin as a bonding agent with. For example, if the river table you are constructing has very porous wood, begin by sealing off the edges before you start pouring in thin layers. 

To resolve epoxy resin not functioning as an adhesive, you may want to sand down the portion you have poured or apply another type of adhesive between the surfaces you wish to bond. Then, proceed with the typical pouring suggestions of your epoxy resin by following the recommended product settings.

9. Loss of Glossy Appearance

If you are noticing that your epoxy resin has lost some of its shimmer and shine, this is typically related to environmental or climatic factors. The loss of glossy appearance can also be a result of the project being unclean (such as having a layer of dust formed on the surface.

To avoid the loss of glossy appearance from your epoxy resin you can be sure to maintain a clean surface on your project. Additionally, you can be sure to store the project in non-harsh conditions and avoid typical wear and tear.

To resolve the loss of glossy appearance from your epoxy resin you can enhance the gloss by cleaning it or by reapplying low heat to reduce the moisture that could have formed within the project. You can also reapply a varnish or topcoat to enhance the glossy effect.

10. Bulging

If you notice your hardened epoxy resin has a bulging surface like that of a citrus peel (orange, lime, lemon, etc.), this is likely caused by temperature variations either during the hardening process or after the product has been catalyzed.

To avoid bulging of epoxy resin will depend if the product has completely hardened or not. If the epoxy resin has not completely catalyzed, you can attempt to apply a very thin (2mm or less) layer of epoxy on the surface in the hopes that it will smooth out. Then, be sure to move your project to a cooler or warmer environment depending on which end of the product’s temperature range you need to adjust to.

To resolve bulging of epoxy resin that has already hardened, you will need to sand down the project until the bulging surface is no longer present. Then, reapply a surface layer and consider finishing with a finishing spray like polyurethane once the epoxy resin has completely catalyzed. This can help to add an additional layer of protection from harsh temperatures and other environmental factors that could cause bulging.

Jedediah Arnold

Jedediah has been working with epoxy resin for a couple of years. When he started, he wanted to share everything he learned as he learned it which continues.

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