What most Tung Oil articles get wrong

I have been using Tung oil as my go-to finish for a dozen years or so.    As far as I am concerned it is a great finish for more things than it usually gets credit for.  Thankfully its virtues are getting shared more often now in recent years.  In my experience it is far superior to Boiled Linseed Oil (BLO).

 
  Pure Tung Oil Boiled Linseed Oil
Durability Tung oil is much more resistant to scratches and scuffs. It is no comparison to harder finishes like varnish or poly, but beats BLO by a long shot Easier to scratch or abrade, easier to damage with liquids.
Longevity Looks the same after a couple of years.  No real tint change in time.  Looks dry and in need of another coat. Darkens with age.
Water resistance Practically waterproof. Low water resistance.
Mold resistance Does not mold Quite prone to mold (mold feeds on it) especially in humid / moist areas.
Color Imparts very little color.  Hint of yellow/honey Darkens a bit, and gets darker with age.
Cure time (dry time)  ~7 days (humid Florida)   ~2 days 
Cost  $$ $
Source Tung “nut”  (it’s a seed not a nut) oil  Flax seed oil and metallic driers
Applications  3-7 ?  3 ?

I find pure Tung Oil (many finishes have varnish and all kinds of other things in them and appear under a Tung label but are mainly not Tung oil) to be easy to apply and the fact that it is more durable and nearly waterproof means I have less to do to keep in in good shape once the piece of furniture or cutting board is put into service.  I also appreciate that it does not feed mold the way BLO does.   In Florida, the humidity makes mold a real threat and common with BLO.

On certain issues, most people give the advantage to BLO, but I think it depends on the long game.

Cost:  BLO is a bit cheaper than pure Tung oil,  but it is prone to damage from water, mold, abrasion, and sunlight, so that means I have to spend more time repairing it.  I’ll gladly spend a bit more money upfront so I don’t have to repair later.

Number of coats:  Honestly, every article I have seen, gives the win to BLO as only needing 3 coats, while claiming Tung needs more like 7.  In my experience, 3 coats of either look pretty much the same.  BLO builds a little faster, than pure Tung oil due to the added driers.  However I look at it like this.  In a year, a piece I finished with BLO will be ready for another coat.  So now I have to take it out of service in my home, to put another coat of BLO on and then wait for a day or two to put it back into service. I have not found that to be the case with Tung Oil.  Once finished, unless the piece is an outdoor piece or gets a lot of traffic, I rarely need to apply new coats of Tung oil.   So over a 10 year spread, I would say the number of coats is about even.  It is just a question of whether you want to do them all up front, or spread them out over the years.  

Curing time: The time it takes for a coat of pure Tung oil to cure (dry) is 2-3x longer than boiled Linseed oil.  Due to the metallic additives, BLO cures in a day or two, while Tung oil can take a week.  Please note, air flow, temperature, and humidity have an influence.  I am a weekend woodworker so that works fine for me.  If I was banging out furniture or cutting boards for clients or retail, Tung oil would not be viable because of the time, and the space I would need to have things cure.   The slower cure time does have one advantage.  Both oils cure by polymerization in the presence of Oxygen, and as a result, release heat.  This hazard is why you have to be careful with oiled rags and how you manage them.   With BLO, the risk of spontaneous combustion is higher because all the curing is happening in a much shorter time.  Which makes it more likely to self combust. 

Durability: Many articles say the durability is the same for pure Tung oil or BLO.  That comparison is not even close.  Tung oil is MUCH more durable than BLO.  The Wood Whisperer did a fantastic comparison of foodsafe oil finishes. It was hands down finish that held up the best, even standing up well to boiling water.

Tung oil direction they ALL get wrong

So far I have covered the minor items for comparison that I think most oil finishing articles get wrong.  However I think there is one more critical direction that they ALL get wrong.  The direction that I see that all the articles and even label directions get wrong is the first coat direction.  They all say to thin the Tung oil with (mineral spirits / turpentine / citrus thinner …) then soak and saturate the wood until it will not absorb any more, and then wipe it off.  The “continue to apply more and more thinned Tung oil until it can’t take anymore” is the bit I think they get wrong.  Tung oil cures by exposure to oxygen.  If you soak the wood completely, the Tung oil that reaches the deepest into the wood will not cure for months or years, because oxygen does not get to it in sufficient quantity.  

My approach for applying a great Tung oil finish:

  1. Apply the first thinned coat liberally with a brush or rag. Fill in thirsty spots a bit for the first 10 minutes.  
  2. Walk away for an hour.
  3. Wipe everything down with a clean rag, or paper towel.  
  4. Hang that rag on a drying rack, nice and spread out so it is not bunched up.  I put a clip on it so it does not blow off.  Pay attention to where this cloth is.  It will be your reference later.
  5. Come back 3 – 5 hours later and wipe down with a new clean cloth / paper towel. This gets rid of any last oil that may seep out of the wood and leave sticky spots.
  6. Walk away for at least three days, though expect more.
  7. Check the cloth you first used to wipe the board down.  When the oil is cured in the cloth and it is kind of stiff, your project is ready for the next coat of Tung oil.  If it is cured in the rag, it has cured in the wood.  You can’t use the wood as the test, because it is misleading. The wood will feel “dry” long before the cloth will act solid. If it is not cured on the cloth, check back each day until it is cured.  
  8. Repeat steps 3 – 7  as many times as needed until you are satisfied with the level of sheen and build.

Patiently waiting for the cloth to become solid in step 7 is what I have found is the key.  If you do not wait for the cure each time, the wood will just keep drinking in more oil that will not cure.  It will take a lot more coats to get the build you actually want.  Rushing it, will leave you disappointed and disgruntled.

What brand of pure Tung oil do I use?

Affiliate links below, but not sponsors.  I have had equally great results with both Hope’s Pure Tung Oil and Milk Paint brand Pure Tung Oil.  I typically go with whichever brand has the best price on Amazon at the time.  I think I may favor the Milk Paint brand a little more only because they have a great cast of supporting products that I also like:

  • Dark Tung Oil which has some dark solids in it that makes a stain and finish in one.  
  • Citrus solvent that I prefer to mineral spirits, for thinning Tung oil for the first application.  They also sell premixed half-and-half or dark-half which is their tung oils mixed with citrus solvent.  
  • Outdoor Defense Oil This is predominantly Tung oil mixed with zinc to make it more resistant to the sun and weather.  I have a few pieces of outdoor furniture that I finished in 2019 that are still holding up quite well.  

Addendum 12/19/22:  Someone passed this article along to me. Tung oil: why and how to use it, by Peter Spaulding.  It has some similar insight about not using so much, but he goes even more”extreme” and suggests using even less and provides ways to cure it faster with even thinner coats and unthinned.  He has raised my curriosity and I definitely want to try his method.

 

Reader's Comments »

  1. By swirt on January 2, 2023 at 9:38 am

    I found this great video related to oil finishes on spoons but can also apply to other things too https://youtu.be/H4PSMx_jHK8