Can You Put Polyurethane Over Tung Oil? (Answered!)

You just finished the final coat of Tung oil on your wooden project, which looks fantastic. Is there anything else you can do for that surface while it dries? 

For example, can polyurethane be applied over tung oil?

The idea of combining polyurethane and Tung oil on wood is intriguing, given all of the benefits the two products bring to a surface.

VIDEO: How To Mix and Apply An Oil/Poly Blend

How long does it take for tung oil to dry and cure?

Pure tung oil requires 24 to 72 hours to dry and a month or more to cure completely. 

On the other hand, Tung oil finishes (oil and varnish blends) dry in 24 hours and require a week to cure completely.

The drying and curing times are affected by the weather. Low temperatures combined with high humidity will slow the drying process. 

Conversely, high temperatures and low atmospheric humidity will accelerate tung oil drying and curing.

Is a top coat even necessary for tung oil?

Tung oil does require a topcoat, especially on frequently used surfaces. Tung oil, like boiled linseed oil, is a drying oil used for waterproofing wood and protecting it from other types of damage.

It is frequently used to highlight the wood grain pattern in natural wood. Although it has been used as a final finish for centuries, its durability differs for many varnish formulations or modern finishes.

Tung oil is also receptive, so you can clear coat it with almost any other protective finish to form a hard solid film surface.

Is it possible to apply water-based polyurethane over tung oil?

Yes, water-based polyurethane can be applied over Tung oil, but only after it has fully cured. So the answer is no if you’re wondering how a water-based finish will work with Tung oil. 

This is because you are layering rather than mixing.

Tung oil and polyurethane, on the other hand, would only work if at least one coat of de-waxed shellac (sanding sealer) was applied to the cured Tung oil wood surface.

 Then, after the shellac has dried, apply a water-based polyurethane finish to the surface.

How to Use Polyurethane on Tung Oil

Polyurethane has numerous advantages for wood surfaces, particularly those coated with Tung or linseed oil. 

Aside from the obvious benefit of a harsher topcoat, polyurethane comes in various sheens.

Matte, satin, semi-gloss, and high-gloss protective finishes are available. Remember that oil-based polyurethane has a yellowish tint and will undoubtedly affect the color of the oiled wood over time.

First, try it in an inconspicuous location. 

Then, if you like the new wood colors, apply them to the entire surface.

We’re applying oil-based polyurethane to an already oiled wood surface for this method. This method works whether the oiled surface is new or well-used.

 Here’s a list of everything you’ll need for this process.

Materials and Tools

• Wong oil
• Polyurethane derived from oil
• A natural bristle or foam brush
• Sandpaper or a power sander
• Lint-free clothes Tack cloth
• Stainless steel wool

 Procedure for Applying Polyurethane Over Tung Oil in Steps

 Step 1: Safety must be prioritized.

First, ensure that your workstation is adequately ventilated, with unrestricted airflow. Then, to catch drips and spills, line the floor beneath with painter’s plastic.

Polyurethane based on oil emits strong fumes that can cause allergic reactions. As a result, wear gloves, a respirator mask, and safety goggles.

 Step 2: Use Tung oil.

If you’re starting with natural wood, here’s a quick overview of how to apply Tung oil. First, sand it to remove any imperfections. Then, finish with 150 grit to ensure the natural wood feels soft.

Depending on the size of the surface, use a power sander or a sanding block. Collect the sanding dust with a shop vacuum or by hand.

 Then, use a tack cloth to go over the sanded surface again.

Apply a generous first coat of oil using a natural bristle or foam brush. Allow the oil to soak into the porous surface for 10 minutes. 

Then, wipe away any excess oil and allow the surface to dry completely (24 to 72 hours, depending on the type of Tung oil).

Layer two to three coats of Tung oil and wait until each previous coat is completely dry before reapplying Tung oil. 

Allow oiled wood to dry for at least a week after the final coat before sealing the Tung oil surface with a protective finish.

 Step 3: Check that the oiled wood surface is dry.

How long has it been since you last applied a coat? A day, a week, or several months? 

Whether you used pure Tung oil or an oil and varnish blend, ensure it is scorched.

Check the dryness by pressing your pinky finger on an inconspicuous area; if it’s soft or tacky, wait another day. If the surface is firm and does not accept your fingerprint, move on to the next step.

 Step 4: Remove the oiled surface.

Once the Tung oil is dry, use a lint-free rag to remove any dust or bristles that may have settled on the surface. This is true for newly oiled wood.

If you have a fairly used Tung oiled surface, wash it with warm soapy water to remove debris. Allow the wood to dry before evaluating its condition. 

For example, is the surface evenly coated, or does at least one coat of Tung oil need to be applied?

 Step 5: Prepare for the oil-based polyurethane finish.

Open the can gently and stir the product with a stirring or clean stick. Stir polyurethane in one direction, from bottom to top, to mix pigment and solvent that may have separated on the shelf.

Unless the product is in an aerosol can, shaking the oil-based finish is not one of the ways to mix it. Shaking polyurethane will cause bubbles and ruin the finish of your topcoat.

Of course, polyurethane bubbles can be sanded off the surface, but why go there when you can avoid it entirely?

Pour some finish into a separate stain bowl. It’s always a good idea to avoid applying the can finish because you might introduce impurities that will prematurely spoil the polyurethane.

We recommend thinning the first two coats in a three-to-one ratio of polyurethane to thinner -mineral spirits. This will give you a professional-looking wood finish.

Step 6: Apply the first polyurethane coat.

Dip your polyurethane brush into the finish and apply a thin coat. Brush the product in long strokes along the grain of the wood.

Go over every inch of your wooden project to ensure that the entire surface is evenly coated.

Apply a light layer of wipe-on poly with a lint-free cloth or a fine-grit scrub sponge.

 Step 7: Allow the polyurethane to dry.

The drying period is the key to the seamless layering of finishes on wooden surface. 

Allow the polyurethane to dry overnight or for 24 hours before applying the next coat. 

Then, for added durability, apply at least three coats of polyurethane.

Step 8: Sand and thoroughly clean the polyurethane layer.

Sand the dried polyurethane varnish surface with 220-grit sandpaper or fine steel wool. 

Gently rub the surface to prepare it for the next additional coat; wipe away dust with a soft rag.

Step 9: For the second coat, repeat steps 6-8.

Reapply the oil finish, and wait for the polyurethane to dry, scuff, and wipe away the dust. 

Remember that you’re still using the thinned stain finish from earlier for this second coat.

Step 10: Apply and cure the final coat of oil-based finish.

The final coat should not be thinned or sanded. Instead, brush or wipe it on, then allow the finished surface to dry and cure for as long as necessary.

 It could take anywhere from three weeks to a month or even longer.

While curing, oil-based polyurethane emits a lot of gas.

Protect yourself and your family from the effects of toxic polyurethane fumes.

Clear your workspace and brushes. Shop rags should be cleaned or disposed of properly. 

 Conclusion

So, can polyurethane be applied over minwax tung oil finish?

 You certainly can. However, before applying polyurethane, ensure the Tung oil surface is completely hardened. 

To some extent, tung oil varnish makes wood floors waterproof and scratchproof. Polyurethane is entirely water and scratch resistant. Coating wood with both products ensures a longer lifespan and a desirable sheen.

 FAQ on Can You Put Polyurethane Over Tung Oil