Tung oil has been mentioned before when talking about natural oils or about Danish oil. Now we will deal with it separately, because it is an important oil for wood finishing that is coming back into favour with the initiated. It belongs to the group of products with a long history in wood protection, together with linseed oil or shellac. In their pure state, they are all natural products and have been used to beautify and protect wood since ancient times. In the last hundred years they have gradually been replaced by products made by chemical processes, which are stronger and cheaper, but not always healthy for people and the environment. In addition, finished with synthetic products, wood sometimes loses its natural look and silky sheen from oils or shellac. Oils have made a comeback and now share the wood finishing market with synthetic varnishes and paints, which have also become safer or less aggressive.
What is tung oil
Tung oil is a natural product obtained from the seeds of the nuts of the tung tree (Vernicia fondii), native to China. It is also called Chinese wood oil (China wood oil), wood oil or walnut oil. The ability of oil to protect wood against water has been known since the time of Confucius (500-400 B.C.), who wrote about methods of treating the wood of ships with tung oil to increase its strength. He also describes treating paper umbrellas with tung oil to make them water-resistant.
Closer to our times, tung oil was burned in lamps for light, then used to make varnishes and paints and even refined for use as fuel. After the discovery of tung oil's qualities worldwide, the tree began to be cultivated in Argentina, Brazil, Paraguay and the USA, which have now joined China as producers of tung oil. The wood of the tung tree (pronounced tong in Chinese) is light but hard and is sometimes used as a substitute for balsa wood.
Tung oil penetrates the wood and makes the film resistant to moisture and ... acetone
Its use as a wood preservative stems from the fact that it polymerises in contact with air, becoming solid. Its liquid consistency allows it to penetrate into the wood and so the protection goes deep (it can penetrate more than 5mm into the wood), giving the wood good resistance to moisture. After finishing, the wood takes on a very pleasant, silky matt appearance, its colour darkens a little and persists over time, without the yellow tinge typical of ageing linseed oil and varnishes. Tung oil contains a very high percentage of a component that reacts in the presence of oxygen in the air and causes it to polymerise at a rate of 100%, resulting in advanced cross-linking that gives the oil its resistance. So, unlike other oils, tung oil is fully cured and can form a film. Also, the bonds formed do not degrade over time, making the tung oil finish durable. The film formed is resistant to acetone or vegetable or fruit acids.
Pure oil dries hard, in a few days. To shorten the drying time, pre-polymerisation is carried out by heating at 260°C in the absence of oxygen. The result is an oil with much higher viscosity and improved film-forming properties. To penetrate the wood, this oil is diluted, at least for the first layer. Organic solvents, white spirit, turpentine or organic thinner made from lemon peel are used for dilution. Pure oil can be used for finishing objects that come into contact with food. If diluted, it loses this ability, except when diluted with organic lemon peel thinner.
How to apply
Finishing with pure tung oil in the traditional style takes patience and time. The oil is applied in several coats and the drying time between coats is long. It takes time to fully cure and maximum strength is achieved weeks after the application process is complete.
To penetrate as deeply as possible into the wood, the first coat is diluted 1:1. Apply with a brush or lint-free cotton cloth. Rags from old t-shirts are best. Apply in excess, leave for 30 minutes for the wood to absorb, then wipe off the excess. Allow to dry for at least 24 hours, then apply the second coat, thinned less (2 parts oil to 1 part thinner). With each coat applied the amount of thinner added decreases. Sand between coats with very fine sandpaper (800-1000) and steel wool. If the sanding results in white dust, the oil is well dried. If the film is gummy, the drying time should be extended.
Between 2 and 5 coats can be applied, depending on how much the wood absorbs and how the film is desired. The last coat is applied undiluted, and it takes up to 30 days for the film to reach maximum hardness and strength. The resulting film has a very pleasant warm brownish yellow colour that does not change over time. It is not glossy and has a silky matt appearance.
The advantage of protecting the wood very well turns into a disadvantage if the top coat has to be removed. If the oil is not yet hardened use thinner, sandpaper and a lot of patience. If it is hardened, a thin layer of wood must be sanded and even removed because otherwise some oil will remain in the pores and grain of the wood.
WARNING! After application, all used rags, oil residues and other auxiliary materials that have come into contact with the oil are placed in a bowl of water. Like all oils, tung oil is also self-combustible. The sun and the heat of summer accelerate the phenomenon, but oil-soaked scraps and rags should also be placed in water in winter.
Differences between tung and linseed oil
Tung oil is often compared to linseed oil because both are used to finish wood. In fact, the mixture of the two forms a very popular finishing product on the market - Danish oil. Both are natural and have long been used traditionally to finish wood. They are valued for the natural appearance of the wood after application and the moisture resistance they give.
However, there are important differences between the two types of oil. Here are some of them:
Unlike tung oil, which polymerises 100% by hardening completely, linseed oil never hardens completely. The remaining uncured linseed oil must be wiped off because it remains sticky without solidifying. Surfaces finished with tung oil are harder than those finished with linseed oil (also due to advanced polymerisation). Linseed oil does not form a film, whereas tung oil does. Linseed oil has a shorter molecule than tung oil and penetrates more easily into the wood without the need for dilution. Linseed oil changes colour over time, becoming more yellow. The colour change in tung oil is almost imperceptible. Pure linseed oil dries much more slowly than pure tung oil. For both the drying time is shortened by boiling. Tung oil is more resistant to moisture than linseed oil. Tung oil is much more resistant to mould than linseed oil. Linseed oil is cheaper than tung oil.Mixing them in different proportions results in very high quality oils for finishing wood surfaces, combining the qualities of the two oils. This results in hard oils for floors or oils that penetrate deep into the wood, oils with a high resistance to outdoor use or cheaper oils for indoor use.
Tung oil as a commercial product
There are many products on the finishing materials market that go by the name of tung oil, but few that are 100% tung oil. Many are blends of various oils, even wax oils, in which there is a greater or lesser amount of tung oil, and this is reflected in the price of the product. The best known blend is Danish oil, but this too has many variations, and in some the tung oil is missing altogether.
There are also products with names that suggest tung oil (tung oil finish), but which do not have tung oil in the formula at all. In order not to be misled, the composition written on the label should be checked. If it is missing, the product is certainly suspect because no one would have an interest in hiding the presence of tung oil in their product.
The best indicator of product quality is price. A cheap product will have a small percentage of tung oil or none at all. But don't be fooled by a high price either. When the product is presented as a quality product, ask for the technical data sheet, product sheet or safety data sheet or read the label carefully. No serious company will hide the composition of the product while charging a high price for it.
Oils are natural products that give wood a special appearance. Those who have seen walnut woodof ulm, from paltin or palisander oiled, I know what I'm saying. The oil really brings out the natural wood grain and design. And tung oil does this best. In addition, it protects the surface and makes it strong and durable. If you work with solid wood, try this finish at least once. You won't regret it.
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Hello. I am building an uncovered terrace (exposed to sun and rain) made of pine wood, 5 cm thick.
Would it be appropriate to protect the wood with tung oil mixed with linseed oil? Thanks
Hello!
Yes, it can be protected if 3-5% pigment is added to the oil mixture. The oils will give a very good moisture resistance and the pigment will protect against UV radiation. As the percentage of pigment is low, the oil mixture will remain transparent, with only a very slight coloured tint.
Good wheels!
Hello,
Can water-based paint be applied over the tung oil treatment?
I want to protect a shed (small and flirty) to withstand the weather, but in the artist's vision it will be white.
What other protective options can you recommend so that the final finish is white.
Thank you!
Hello!
Water-based paint over oil is not recommended, even if there is a film.
You can use white oil-based paint, alkyd paint or white pigment to add to the oil (25-30% for paint, 3-5% for varnish).
Make sure the paint is for the outside because otherwise it will yellow.
All the best!
A reliable source where can we buy tung oil? Thanks in advance.
Good evening!
From what I've heard from carpenters, Fine Tools has a quality tung oil. I haven't tested it. If you want blended product - tung oil and linseed oil - Kreidezeit is a brand with quality products for both exterior and interior.
All the best!
Good evening. Thank you for your articles; I follow them with great interest. I am about to purchase a house made of cherry wood (spruce) that will arrive as a kit that will have to be assembled/finished... So I started to research, to find out that wood is indeed a noble material that demands due respect. In one of the rooms there will have to be the bathroom and that gives me a big headache. After setting up a solution to finish the walls/floor of the bathroom I found this gentleman, who seems to know what he is talking about https://www.youtube.com/watch?v=6CYD9Hw71j4 and who is very sceptical about any finish (ceramic tiling...) on wood substrate; and not because of moisture inside (even in case of perfect waterproofing) but because of moisture outside. In other words, the outside faces of the bathroom (walls/floor) should not be treated with less care. Do you think that the products presented in your article can bring a solution? Anyway the prospect of brush painting, more "hands" , a 40sqm house is daunting. A spray gun solution would be more credible. Thank you.
Hello!
Thanks for your appreciation!
Oils are the option adopted by many builders of round timber houses or rectangular beams. I know a manufacturer who has been making log houses for many years and finishes them on the outside only with oils. It is true that on the inside he does not and never recommends fitting ceramic tiles directly to the wooden wall. Primarily because of the settling of the wood over time which can lead to cracking of the tiles. It is mounted on gypsum plasterboard which is mounted at a small distance from the wooden wall. That distance is very important in the case of the phenomenon you are talking about. Avoiding condensation that can lead to wood rot is all about air circulation. This circulation allows the wood to dry and keep it in balance with the surrounding humidity. This is a very important principle of wood construction. In an inhabited house, there is a possibility of dampness (burst pipes, flooding due to negligence, etc.). Water reaches even the most hidden places and there must be a possibility for the area to dry out. And this is only possible if air is allowed to circulate.
I think oil is a good option for outdoor application. It can also be applied with a spray gun using white spirit (petrosin) or turpentine oil for dilution.
All the best!
Good evening,
I recently discovered your site, very informative, well structured, congratulations for your time and effort.
You recommend linseed or tung oil for treating and conditioning wood, but in the case of garden benches or in general when you are in direct contact with wood by touch, does it stain clothes or other textiles? Can a coat of colourless varnish be applied over tung oil/in?
Thanks in advance.
Hello!
Thanks for your appreciation!
Oil and wax were the first products used to protect wood. And now there is furniture that is finished by oiling or waxing. If applied correctly, after drying for 24 hours, you will have no problems even if you sit on an oiled or waxed surface.
Tung oil forms a film and does not need to be coated with a varnish. But if you want, you can apply a coat of varnish over the tung oil film.
Linseed oil does not form a film. The excess left on the surface must always be wiped off because otherwise it becomes sticky in contact with air, not hardening as tung oil does. But if it is wiped off, oiled and left to dry for 24 hours, it won't cause problems. Linseed oil can only be coated with oil paint, varnish or alkyd oil, in general with products that have white spirit (petrosin) as a thinner. Water-based products or organic solvents cannot be used.
The wood preservative oils now available commercially are blends of natural or natural and synthetic oils. Pure linseed and tung oils are rare and expensive. The finishes are so made that they dry well and quickly enough so that they don't create problems in use.
All the best!
Hello! I am also a beginner in woodworking and I have spent a wealth of information in your articles for which I thank you too! I also have a question: I make wooden articles for pets and I keep looking for a better way to protect my products from moisture (because some of them urinate in them) and I came to this tung oil and I need this film to be not toxic at all because they are used to rodents and so they can ingest that film. From what I understand from the article, to make it as safe as possible, lemon peel thinner can be used for dilution, but I can't seem to find it anywhere, maybe I don't know how or where to look for it. What can you advise me on this? Thanks in advance!
Hello!
Try Fine Tools. For dilution you can also use turpentine (made from resinous buds).
You can also use mineral oil. It is recommended for finishing wooden dishes in the kitchen, those that come in direct contact with food. You can find it at the chemist's and it is more fluid, you may not need to dilute it. Below is a link to information about this oil and other materials that could be used.
All the best!
https://revistadinlemn.ro/2019/07/11/protejarea-vaselor-de-lemn-din-bucatarie-cu-materiale-netoxice/
Thank you very much! I also saw the mineral oil but I didn't know where to look for it, on the internet only the auto one shows it.
Health and all the best!
Hello! I have another question, if I'm not disturbing: what would be better against wetness and more resistant in time between tung oil and a water-based varnish?
Hello!
If well applied and no cracks occur from wood movement, water-based varnish, if of very good quality, has greater resistance over time.
But I would choose tung oil. To achieve long-lasting resistance to a water-based varnish there are many variables and conditions that need to be met.
All the best!
Hello,
please help me with some advice if possible:
- oak wood
- I use products from Borma Wachs (turpentine and tung oil)
I finished the oak to 500 grain, applied with a rag a layer of 50/50 tung oil mixture diluted with turpentine, left for 15 min and then wiped off the excess with paper (kitchen towels), left for 2 days to dry at about 20 degrees in an area with a constant draft.
I finished with 500 gr. enamel then I applied with a rag a layer of tung oil, left for 15 min then I removed the excess with paper. It has 2 weeks in these drying conditions, it looks dry to the touch but in the light you can see some spots with a different sheen than the rest of the wood which has a more matte sheen - specific to tung oil.
Why do I have these uniformities? - Where did I go wrong?
Thank you.
Hello!
My opinion is that you have used far too fine a grit for sanding wood and thus reduced the oil absorption inside. 500 is a grit that is used when sanding between coats to achieve glossy surfaces. By sanding this way, the resulting fine dust got into the wood and into the pores reducing the absorption greatly. The first layer of oil stayed longer on the surface and formed a fine film which, using 500 grit, you polished more. The second layer remained more on the surface and was removed by wiping. The shinier areas are where the first coat formed a thicker film that was polished off.
For sanding oak, a 180 grit is more than sufficient. Between coats, for matt finishes, 280 or 320 grit is used. For glossy finishes it is recommended that sanding between coats is done with a minimum grit of 400.
All the best!
Thank you very much for your answer.
As an informative question - does tung oil have a shelf life? I didn't find anything about this on the box.
It must be kept in a covered box because it reacts with oxygen in the air.
Even in the covered box after unsealing, the oil can form a hardened puddle on the surface. But if you remove this puddle, the oil is liquid underneath.
Hello,
I gave it an oak top with Hornbach tung oil. I choked the underside to "do my hand". I proceeded as seen here, gave it a coat of plenty, after 30 min I wiped it off. I didn't thin it. After 24 hours, getting ready for the second coat, I turned the countertop over to see how it appeared on the uncoated side and saw a leftover spatter from neglect that wiped off as if it had been oiled then. Shouldn't it have been somewhat hardened?
I used a kitchen sponge, I said it sure doesn't leave lint and I can scrub better than a brush to penetrate better. On the first coat I used the thin side, on the second the rough side (I smudged before coat two with 320 with orbital, but quite quickly). And the sponge stayed as I left it, not at all thickened from day to day. The rags I wiped with I put on a concrete, didn't put them in water and they were normally cold after two hours, so no question of self-combustion.
Is it normal for oil to be a fake? Yet it's not picked up on the street corner. It says so on it, tung oil. The consistency is like olive oil and it's roscovan. I like the look, it's just right.
Thank you
Good evening!
It's supposed to be tung oil, but there are many fakes on the market. From the behaviour it looks more like linseed oil than tung oil. There is also the possibility that it is uncooked salt oil that dries very hard. But I doubt it would be sold in a DIY store.
Bitches don't always light up. The risk is high in summer or if the sun beats directly on them.
Wait 2-3 weeks and see what happens/ If it dries and looks good, it may be tung oil.
Good luck!
Thank you.
Hello,
It's ok, it's hardening, the best I noticed on the used rags, I didn't throw them away precisely because they were the best clue for hardening, on the countertop surface it's a little harder to notice, there's still the appearance and behavior of a wet surface.
Thanks again. Apart from the sound advice you give me, you also give me the confidence that, at the drop of a hat, at an impasse, I have someone to turn to. I am working on converting a van to a caravan and have various situations regarding woodworking and finishing.
Esteem!
Hello!
You're welcome! Glad that's settled.
Regarding the van conversion, you can contact me about wood issues by commenting on any article I sign.
Good luck!
Hello and thank you gratefully for this valuable information.
I have to finish some wooden interior walls on the yacht. I'm guessing the walls are marine tego. The yacht is from 1989.
The walls were sanded in the summer of 2019 and have remained that way since then until now in 2023.
Can I use this tung oil? My big fear is that it will catch fire. Even though it's inner walls, it's hot inside. And sometimes the sun even gets on the wall.
And how long do I use the oil on the walls can I stay on the yacht? Or does it smell strong?
I also have some kitchen furniture also made of marine tego that I would like to give with this oil. Would that be ok?
Thank you with gratitude!
Good evening!
It can be used without problems, oiled walls do not catch fire just from the heat inside. Once hardened, it no longer poses a danger. Care must be taken with debris and soaked rags when finishing. They should be put in water containers, covered and then disposed of.
The better the protection, the better the wood absorbs. Before applying the first coat, it is a good idea to sand the plywood once more with 120 or 150 grit sandpaper to open up the wood fibres.
The smell is oil specific, not nasty. I recommend using turpentine balsam oil for dilution instead of whore spirit. It is a natural solvent from pine wax. It is more expensive, but has a very pleasant smell.
It can also be used for kitchen furniture. The mechanical resistance is lower than on surfaces coated with synthetic hardening varnishes, but sufficient.
You can find out more about turpentine conditioner in the link below.
Good luck!
https://revistadinlemn.ro/2022/01/13/uleiul-citric-si-cel-de-terebentina-solventi-naturali-pentru-ulei-si-ceara-folositi-si-pentru-degresarea-suprafetelor-sau-curatarea-ustensilelor/
Hello. I have a cello that I cleaned of the old varnish and applied 6 coats of Borma Tung Oil. It looks great. I waited 5 days between coats. Being a musical instrument, which has to resonate, I thought I would apply a coat of varnish as it is very much touched by the hand. Which varnish do you recommend? I want to apply a clear coat so that the colour of the instrument stays like that and doesn't affect the sound. Thank you.
Hello!
As a sounding board instrument, elastic varnishes are best suited. You can use shellac or nitrocellulose varnish.
You need to pay attention to grip and compatibility. If the tung oil was not pure (had linseed or synthetic oil in its composition) it is possible that the nitrocellulose varnish will not adhere or will crack when drying. Check compatibility on a sample or in a less visible place.
If you fail with nitro varnish, an alternative that does not create adhesion problems is alkyd varnish. Unfortunately it lacks the clarity, beauty and warmth of nitro lacquer.
My opinion is that if you leave it longer to dry, the tung oil will form a very resistant film that you can polish, manually or mechanically. The instrument will look great, can be easily maintained, and if it needs a refresh, just apply 1-2 more coats of tung oil.
Good luck!