A common concern with many types of epoxy resin is the possibility of it yellowing. Though rare for higher-end epoxy, it can still occur, but is usually the result of preventable mistakes.
Knowing how to deal with this issue in advance can save you time, money, and a headache. In this article, we'll explain why epoxy yellows, which epoxy to use to avoid it, and what to do for your epoxy to prevent.
Why does epoxy yellow?
Yellowing in epoxy has a number of causes, ranging from production to environmental to sheer mishandling.
Here's a quick rundown of common reasons for yellowing in epoxy:
- Use of low-quality epoxy products
- Contaminants and chemicals
- Incorrect mixing ratios
- Poor curing conditions (i.e., humidity and temperature)
- Excessive heat exposure
- Exposure to UV radiation (usually direct sunlight).
- Age or gradual oxidation
7 common causes of yellowing in epoxy resin
Yellowing in epoxy resin tends to diminish the clarity and appearance of a project over time. Fortunately, there are ways to prevent most of these issues. Below, we'll take a look at them, one by one, in the order they might first occur.
Cause #1: Using low-quality epoxy
Choosing an epoxy is one of the most important steps to planning an epoxy project. Because there are so many subpar epoxy products available these days, it's easy for users to end up with low-quality epoxy that features impurities, fillers, or other problems related to corner-cutting during manufacturing. These low-quality epoxy products also lack UV stabilizers, which can lead to additional yellowing due to increased vulnerability to sunlight and other UV sources.
To avoid this issue, it's essentail to choose a high-quality epoxy resin from a credible source.
At UltraClear, our epoxy resins are all 100% made in the USA—preventing the pitfalls of imported epoxy—and each one is produced to exacting standards that not only meet but also surpass the regulatory guidelines for epoxy resin.
You'll find our premium epoxies on the following pages:
- UltraClear Bar & Table Top Epoxy—Our strongest resin, with self-leveling attributes that make it perfect for finishing most fixtures and furnitures.
- UltraClear Deep Pour Epoxy—Our deep casting resin, capable of exceptional layer depth (up to 2 inches!). The ideal choice for river tables and other projects that call for thickness.
- UltraClear Art & Craft Epoxy—Our specialty craft epoxy designed for resin art projects. It has the strengths of both other epoxies but excels at neither.
Each of our epoxy products provides a strong, crystal-clear finish for convenient, long-lasting results.
Cause #2: Chemical contamination
A second potential cause of yellowing is through contamination of the epoxy, which can happen at any point after the components have left the bottle. Common examples include from the use of harsh chemicals or abrasive cleaners, which can damage the resin and cause it to yellow.
Be mindful about the types of chemicals you use to cleaning your epoxy surfaces. Since their smooth composition allows for easy cleaning, it's rare that you'll need a strong solvent.
It's also possible for oils, grease, and other residues to thwart the curing process and potentially lead to yellowing. Always prepare your substrate surface prior to applying any epoxy.
Cause #3: Incorrect mixing ratios
Any two-part epoxy (which is almost all epoxies) must be measured and mixed together in the right correct ratio of resin to hardener. For some epoxies, this is 1:1, but others may use 2:1, 3:1, or even 5:1.
Measuring out a batch using the wrong ratio can cause a variety of flaws to manifest, including higher likelihood of yellowing after the epoxy has cured.
Always make sure your epoxy has been measured to the appropriate ratio.
After measuring, the epoxy components must be mixed. It's generally not difficult but must be done thoroughly.
Read and follow your chosen epoxy's mixing instructions carefully.
Cause #4: Poor curing conditions
After epoxy has been applied, it must be allowed to cure, either partially before additional layers, or completely to allow for a fully usable surface. Regardless, the curing must be done within a suitable range for both temperature and humidity.
Most epoxies cure best at about 75°F. A few degrees higher or lower won't ruin it, though it may make the process take longer.
For humidity, the typical guideline is below 60%. This will avoid issues with moisture seeping into the resin and marring the results.
Get the most out of your epoxy by avoiding these common curing mistakes!
Cause #5: Ultraviolet (UV) exposure
For outdoor epoxy projects, sunlight exposure is a frequent source of yellowing. UV radiation from the sun can gradually yellow epoxy. Though higher-quality epoxy can resist this change for longer, it eventually will occur within any finish that is consistently exposed.
Fortunately, this problem can be avoided in a straightforward way—by providing cover. Whether natural or fabricated, providing your epoxy surfaces shade or shelter from the sun's rays will prevent them from doing the kind of damage that leads to yellowing and other concerns.
Though rare, it's also possible for indoor projects to suffer this issue. Generally, this will only occur with UV lighting, which few people use regularly, so it's almost certainly not an issue you'll encounter.
Understand how to keep your epoxy safe from the sun and other elements in our outdoor guide.
Cause #6: Exposure to heat
Excessive heat can stress epoxy and induce chemical reactions that cause it to yellow and degrade. Avoid exposing your epoxy surfaces to consistent temperatures over 125°F, and definitely watch out for temperatures above 145°F, which can cause more immediate damage.
Thermal shock can cause discoloration as well. This is a sudden, rapid temperature change that stresses the finish, weakening it.
Learn how epoxy fares with heat in our guide to the topic here.
Cause #7: Age and oxidation
Finally, the passage of time is also an inevitable concern for epoxy (and every other material). As an epoxy finish ages, oxidation may occur. This can lead to yellowing or other issues.
Most epoxies last a few years, but high-grade epoxy can endure for 7 years or more. When choosing an epoxy, consider the long-term costs of maintenance. A premium epoxy will last longer, require less upkeep, and retain its clarity better.
Quick tips for preventing yellowing in epoxy resin
To minimize the risk of yellowing, consider the following preventive measures:
- Use UV-resistant epoxy: Choose epoxy formulations that include UV inhibitors or stabilizers to protect against sunlight-induced yellowing.
- Control the curing environment: Maintain stable temperature and humidity levels during the curing process to ensure proper hardening.
- Follow mixing instructions: Adhere strictly to the recommended resin-to-hardener ratios and mix thoroughly to achieve complete curing.
- Avoid harsh chemicals: Clean epoxy surfaces with mild soap and water, and avoid abrasive or chemical cleaners that can damage the resin.
- Limit sun exposure: Position epoxy projects away from direct sunlight or use coverings to reduce UV exposure.
- Use high-quality products: Invest in reputable epoxy brands that offer higher purity and include UV stabilizers to enhance longevity and resistance to yellowing.
UltraClear Epoxy: Resin products of unmatched quality
As with any material, epoxy resin has both pros and cons. But no other sealant has so few weaknesses, and that's what puts epoxy above all other options when it comes to being a finish for high-traffic fixtures and furniture such as countertops, table tops, and bar tops. And among epoxy resin products, there are none that match the quality of UltraClear.
You can find our UltraClear Epoxy products on the following pages:
- UltraClear Bar & Table Top Epoxy: The classic choice for bar tops, countertops, and table tops. Rock-solid, waterproof, and crystal-clear.
- UltraClear Deep Pour Epoxy: Our deep pour casting resin. Ideal for thick layers, such as those needed for river tables.
- UltraClear Art & Craft Epoxy: Our arts and crafts resin, designed for smaller artistic endeavors which typically involve resin molds and require a bit more fluidity than bar top epoxy.
Epoxies that endure, with minimal upkeep
With high chemical and physical resistance, UltraClear resins can withstand and endure many forms of wear and tear without breaking a sweat or showcasing any cosmetic damage.
Plus, in addition to its ease of application, they also require little upkeep to maintain its pristine appearance. With a high-quality epoxy finish, you can expect a minimum lifespan of 7 years, with no need for reapplication. Beyond that, it's a breeze to renew that coating, requiring only a light sanding and a fresh layer of epoxy.
Expert support from our resin specialists
For more information about epoxy, or for assistance with your epoxy project, contact us at UltraClear Epoxy, where you can speak with one of our epoxy experts. During business hours, you can also text chat online with one of our resin specialists by clicking the Help button at the bottom of your screen.
