Epoxy resin has fast become one of the most popular ways to give tables, or a kitchen countertop, a unique and fantastic finish.
So, how do you turn a satin epoxy finish into a high gloss one? By coating it with a clear varnish, of course!
However, epoxy resin can be tricky stuff to work with if you want that countertop to be perfectly even and high gloss. That is because while sanding epoxy, (both between coats of epoxy and after), helps with adhesion, it does little to keep epoxy looking glossy.
Which is why top coating epoxy with a thin layer of clear varnish should be enough to give that table top its sheen back. That varnish will not only gloss up scuffed epoxy, it can even give it UV protection too (since epoxy doesn’t do well on its own when exposed to direct sunlight).
But, what if in the process of applying varnish over epoxy, you’ve found yourself running into a bunch of problems?
Some of the most frequent problems people have – when trying to get these two finishes to get along – relate to adhesion and drying issues.
To be more precise, your varnish coat might struggle to cure atop epoxy. Plus, epoxy isn’t the easiest of substances to get smooth.
To that end, in this post, you are going to learn why sanding epoxy (and the sandpaper grit you use) is a key preparation step for a varnish top coat.
You will also learn why a dry epoxy resin isn’t quite the ‘cure’ to your varnish adhesion problems.
Plus, discover why sticking to applying a pure varnish coat is best practice (hint: you don’t want to use a varnish/oil blend).
So, let’s get started…
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Can You Really Apply Varnish Over Epoxy Resin?
Varnish will easily layer onto epoxy resin, but with one key caveat… that epoxy resin must be wholly cured. Dry epoxy simply hasn’t hardened enough yet to take on a varnish coat.
Now, the key difference between a dry epoxy and cured epoxy is… chemistry. Dry epoxy has gone through an evaporation process that has seen it turn from a wet liquid into a soft solid.
However, it is only once epoxy goes through curing – a chemical process that changes it into a hard solid – is the ‘drying’ process fully complete.
Related Post: Varnish Not Drying? (How To Fix That Sticky Varnish Problem)
So, How Long Should You Wait For Epoxy To Cure Before Varnishing?
It can take anywhere from 1 to 4 weeks for epoxy to cure all the way through. And much of that timing depends on humidity, room temperature, air circulation, and so on.
But, after 5-7 days, keep checking the epoxy once a day to see if it’s hardened up. If you can still leave an indent in it with a press of your finger, then it needs more time to cure.
Also, you can speed up the curing process by turning up the dry heat. Even as little as a 50° Fahrenheit (10° Centigrade) rise in room temperature can halve the total time it takes for epoxy to cure.
Does Epoxy Always Need Sanding Before Applying A Varnish Top Coat?
Epoxy will always need a bit if sanding prep if you want anything to coat onto it. It’s surface is just too polished otherwise.
By sanding, you create a bit of texture for varnish to cling to as it dries. However, make sure the surface is clean of all dirt and dust before you go varnishing onto it.
And, quick hint, use a lint-free cloth that has been lightly dampened with water (and nothing else). This’ll be enough to wipe things clean, without leaving anything behind.
Can You Put Epifanes Clear Varnish Over Epoxy Resin? Yes, this high gloss clear varnish will stick to epoxy perfectly well. However, best practice still applies… you must wait for epoxy to cure first.
But, Wont Epoxy Resin React With Varnish?
Nope, it shouldn’t react at all once epoxy has completed curing. However, if you apply varnish before the curing’s done, then that varnish too will struggle to dry and cure too.
In short, varnish on uncured epoxy will end up congealed and sticky.
OK, So What Are The Top 3 Problems With Applying Varnish Over Epoxy?
1). The Epoxy Is Uneven
If you want your varnish coat to be even, you need to make sure the epoxy resin is even first. The best way to do this is to make sure the epoxy fills every nook and cranny of that wooden surface.
Simply pouring epoxy won’t cut it here. The only way to apply epoxy thoroughly is by using a wood putty tool.
Scrape the epoxy onto that wooden countertop, taking time to carefully make sure you fill in all gaps and cracks too.
Once done, leave the epoxy to cure before you sand it in preparation for varnish.
Use a high grit 220 sandpaper to lightly scuff up that resin. The sanding will take away all of epoxy’s sheen, but the varnish coat will soon bring that back afterward.
2). Don’t Blend That Varnish
Varnish is widely used to help oil finishes dry faster. Add varnish to Linseed oil and you have yourself a form of Danish oil that’ll cure in half the time of Linseed oil alone.
Related Post: Can You Really Varnish Over Linseed Oil?
But, when it comes to epoxy, you should only use 100% clear coat varnish. Don’t go mixing up a recipe of varnish cut with other things.
Stick to applying just varnish onto epoxy, and don’t blend that varnish with any oil finishes. An oil finish will need to penetrate wood to work best, (which it can’t do because of the epoxy barrier). Plus, the oil will simply slow down varnishes drying speed (without bringing any real benefit).
3). The Epoxy Is Cloudy
This is a frequent problem because that cloudiness is caused by moisture getting into epoxy as it cures.
Basically, this happens if epoxy is exposed to high humidity, (anything above 75% humidity), as it cures.
Keep that epoxy dry, (and maybe use an air humidifier to boot), and you shouldn’t have any problems with cloudy epoxy.
Will Even Water-Based Varnish Go Over Epoxy Resin?
Both water-based and oil-based varnish will happily stick to a cured epoxy surface.
Related Post: Can You Apply Epoxy Over Danish Oil?
To Wrap Up, Here Are The 3 Key Takeaways…
- Allow epoxy to cure first before you apply varnish onto it.
- However, patience is a virtue, because epoxy can take up to 4 weeks to cure (depending on the humidity).
- But once epoxy has hardened, simply give it a light sand (with 220 grit sandpaper), and clear varnish will stick and stay on that resin.
