If you want that natural wood to really stand out, then a clear coat of epoxy is a great way to do it.
Epoxy resin really brings out the fantastic look of natural wood grain like no other sealer.
But, if you’ve already added a Tung oil coat, you may run into a problem with epoxy. Which is? Well, epoxy and oil don’t really get along.
You see, if you apply epoxy onto a Tung oil coat that hasn’t fully cured, then that epoxy top coat will struggle to hang on. Any kind of grease pretty much repels epoxy.
So, here’s the thing; there is a key difference between an oil drying and an oil curing.
When Tung oil dries, we are describing it having turned from liquid into a solid film. This usually takes around 24 hours.
When Tung oil cures, however, we are describing it having turned from a solid film into a hard durable resin. This slow curing process usually takes Tung oil blends days. And in the case of pure Tung oil, don’t be surprised if it takes over a month for it to cure.
Now, here is where some people tend to make their first mistake. When you apply epoxy to any natural oil finish, you absolutely must be patient and wait for the oil finish to wholly cure. Otherwise, that epoxy simply won’t bond to that surface.
So, can you apply epoxy over Tung oil?
Yes, you can, but only once you are very sure the Tung oil has cured completely. Which means it has turned into a hard resin coat both on the surface, and underneath.
Still a bit confused? Well, keep reading to learn more about how best to apply Tung oil so that your epoxy coat finishes off with a flourish…
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First Off, What Does Tung Oil Do To Wood?
This natural wood finish makes wood water resistant. Prior to modern technological advances in wood finishes, Tung oil was used to make boats for centuries.
This finish works best by soaking into wood and coating those wood fibers underneath the surface. So that if water or moisture gets in, the wood fibers won’t swell and cause wood to warp.
Related Post: Why Is My MDF Board Warping? (+ How You Can Fix It)
So, Does That Mean Tung Oil Seals The Wood?
Tung oil protects wood, but it doesn’t seal it.
Water-resistant is one thing, but making wood water-tight is a whole other level of waterproofing.
Tung oil can combat moisture and swelling. But it won’t protect wood if you test it against regular water spills, rainwater, or high humidity environments.
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Does Tung Oil Waterproof Wood At All? Or Is That A Myth?
Pure Tung oil offers waterproofing resistance to moisture. It is not, however, a water tight seal.
Although you can purchase Tung/Urethane blended products that claim to be sealers, even those blends are not 100% waterproof. They too will require a sealing top coat, just like pure Tung oil.
And Can You Go Ahead And Put Epoxy Directly Over Tung Oil?
Yes, but once again, only if you are sure that Tung oil has cured.
This is a little tricky to do, since everything from humidity to tempreture to airflow can all effect how long it takes Tung oil to cure.
Related Post: Tung Oil Not Drying? (3 Simple Ways To Fix It)
But no matter what type of Tung oil you use, after you’ve applied that last coat, it is better to err on the side of caution.
Which means that regardless of the curing time claimed on the product label, give it at least a month to cure before adding anything on top of Tung oil. Just to be sure.
And Can I Put Epoxy Over Any Other Oiled Wood Finishes?
If it is a drying oil, (and provided that oil has cured), then yes you can.
You can apply epoxy over Tung oil, Linseed and even Danish oil. You cannot, however, apply it over non-drying oils such as Mineral oil.
Related Post: Can You Put Epoxy Over Linseed Oil (For A Longer Lasting Finish)?
So To Sum Up…
If you wait for Tung oil to fully cure, then epoxy will adhere to it without issue.
But don’t rush ahead to apply epoxy before Tung oil is ready. Because the uncured oil molecules in Tung oil will shrug off that epoxy resin like a shawl.
Efficacy of linseed- and tung-oil-treated wood against wood-decay fungi and water uptake – ScienceDirect