A coat of varnish can give any wooden surface a fantastic glossy finish. Which is in stark contrast to Tung oils matte coat.
But while varnish can give wood a glossy look, Tung oil is often better at preserving wood. So, is there a way to combine the two and coat varnish over Tung oil?
Well, in this post, you’ll learn whether or not Tung oil really needs a top coating seal — and why. You will also find out why Tung oil isn’t the most water-resistant wood finish.
And keep reading to discover whether varnish is the right sealant for your Tung oil finished wood craft.
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Does Tung Oil Even Need To Be Sealed? Or Is It A Durable Finish?
Well, general rule of thumb, you can use Tung oil as a top coat. And, if that Tung oil coated surface doesn’t see a lot of usage, then this finish can last.
But, this is not a durable finish, and it is certainly not the most water-resistant sealer you can put onto wood.
First off, it needs to be reapplied every few months — especially if it is applied onto exterior wood.
On top of that, Tung oil is a microporous finish. And what that means is that while it can block water droplets, it doesn’t prevent water vapor from getting past it.
So, pure Tung oil finishes can become damaged if you left a wet condensation covered glass on them.
Last but not least, Tung oil is a rigid finish (after it has cured). So it can become scratched more easily than say polyurethane (which has a little more give to it).
In short, Tung oil doesn’t need a seal, but you won’t go too far wrong sealing it anyway.
Will Tung Oil Waterproof Wood? Tung oil is a microporous wood finish that is very water-repellent, but it is not 100% waterproof. So water vapor, (humidity, steam, and so on), will sink past Tung oils resinous coat.
Can You Put A Clear Coat Of Varnish Over Tung Oiled Wood? Will That Seal It?
You could, and varnish will adhere over Tung oil.
However, if you’re hoping that varnish will protect that Tung oil finish, then prepare to be disappointed. Varnish is about as durable as Tung oil itself.
Except varnish is often more susceptible to water damage. And, in some cases, certain varnishes can dissolve if they come into contact with alcohol or vinegar.
So, if you want to put a durable sealant over Tung oil, you’re better off using a urethane-based finish, such as Polyurethane.
But, if you’re applying varnish in order to give Tung oils matte appearance a more glossy look, then varnish will work great. However, make sure you’ve given Tung oil time to cure before you do.
What Do You Mean By Curing? Isn’t It The Same Thing As Drying?
Not at all.
Drying and curing are two different processes that most wood finishes go through. When Tung oil dries, it has gone through a process of evaporation. And this turns it from a liquid into a soft film.
However, curing is a separate chemical reaction process that takes much longer than drying.
When Tung oil cures, the very chemical bonds of this oil changes, turning it from a film into a hard resin coat.
Now, Tung oil may take only a handful of days to dry (in the right conditions). However, this slow-drying finish can take weeks (around 30 days) to cure all the way through.
Related Post: Tung Oil Not Drying? (3 Simple Ways To Fix It)
But My Can Of Tung Oil Says That It Will Cure Much Faster Than That…
In which case you probably don’t have a can of pure Tung oil. Instead, you likely have a can of Teak oil masquerading as Tung oil.
You see, a lot of Tung oil products on the market carry the name Tung oil, but they are anything but. If you take a look at their list of ingredients, they may contain natural oils such as Linseed or Tung oil. However, those natural oils are blended with solvents, thinners, and sometimes even varnish.
In other words, these not-Tung oil finishes are more Teak oil than Tung oil. However, real 100% pure Tung oil is a very slow-drying finish that’s naturally sourced from the seeds of the Tung tree.
To Wrap Up, Here Are The 3 Key Takeaways From This Post…
- 1). Tung oil isn’t a very durable finish. If applied to a regularly used wooden surface, it will need a durable top coating sealant.
- 2). Varnish will add gloss to any matte Tung oil finish. However, varnish is not a durable sealer (compared to say polyurethane).
- 3). Pure Tung oil takes days to dry, and can take up to 30 days to wholly cure. If your can of Tung oil promises faster drying times than this, then it’s likely not a can of Pure Tung oil.