Does Tung Oil Go Bad?

We like oil finishes on our woodworking projects.  They create a beautiful finish, accentuate grains, and offer great protection for the wood surface. There are a variety of oils that work well on wood, and we’ve written about some of them, including linseed oil and boiled linseed oil, Danish oil, and teak oil.

We’ve also written of tung oil and will do so again today.  Shelf life is an important consideration in the woodworking shop, and understanding the products we store and how best to store them for maximum shelf life is part of our work.

What is tung oil’s shelf life?  Can it be extended?  How can you tell if tung oil has gone bad?  All good questions, and we’ll answer them for you today. 

In this article, we are referring specifically to pure tung oil.

What is Tung Oil?

Tung oil is a natural drying oil, and we’ve used it on past projects with excellent results.  It is extracted from the seeds of the tung tree (Vernicia fordii). 

The tung tree is native to southern China, Myanmar, and northern Vietnam. It is also grown in other parts of the world, including the United States, Brazil, and Argentina. The tung tree is a deciduous tree that can grow up to 20 meters tall. It has a spreading crown and smooth, gray bark.

The leaves are large and lobed, and the flowers are white or pink. The fruit is a capsule that contains two seeds. The seeds are the source of tung oil, which is a valuable drying oil.

The tung tree is a fast-growing tree that is tolerant of a variety of soils and climates. It is also resistant to pests and diseases. The tung tree is a popular choice for landscaping and is also grown for its seeds.

It is a clear, yellow-brown liquid that hardens over time to form a hard, durable finish. Tung oil has been used for centuries as a wood finish and is prized for its water resistance, durability, and high gloss.

It can be applied by brush, roller, or spray. Tung oil should be applied in thin coats and allowed to dry completely between coats. The number of coats will vary depending on the desired finish.

It’s not just a wood finish, though, and can be used on materials such as concrete, stone, and metal, too, and not just wood. It can be used to protect these materials from water, moisture, and weathering, just as it does for wood.

Tung oil is a safe and environmentally friendly product. It is non-toxic and does not contain any harmful chemicals. Tung oil is also biodegradable and can be recycled.

Here are some of the benefits of using the oil on your woodworking projects:

• Water resistance
• Durability
• High gloss
• Easy to apply
• Safe and environmentally friendly

How Do You Use Tung Oil?

Using the oil as a wood finish is no different than using other oil finishes like the ones we mentioned earlier.  Preparation of the wood, obviously, is an integral part of the process, and the steps taken when using the oil are not difficult or surprising.

1. Prepare the surface. The surface should be clean, dry, and free of dust, dirt, and grease. If the surface is already finished, it should be sanded to remove the old finish.
2. Thin the oil. Tung oil can be thinned with turpentine or mineral spirits. The amount of thinning will vary depending on the desired finish. For a satin finish, thin the oil with 1 part turpentine or mineral spirits to 1 part tung oil. For a matte finish, thin the oil with 2 parts turpentine or mineral spirits to 1 part tung oil.
3. Apply the oil. Apply the oil to the surface in thin coats using a brush, roller, or spray. Allow each coat to dry completely before applying the next coat. The number of coats will vary depending on the desired finish. For a satin finish, 3-4 coats are usually sufficient. For a matte finish, 5-6 coats may be needed.
4. Buff the finish. Once the final coat of oil has dried, buff the surface with a soft cloth. This will help to bring out the natural beauty of the wood and create a smooth, even finish.

Here are some additional tips for using tung oil:

• Work in a well-ventilated area.
• Wear gloves and eye protection when working with tung oil.
• Allow the oil to dry completely between coats.
• Buff the finish with a soft cloth after the final coat has dried.

It’s a natural product, as we said, and it takes time to cure. It is important to allow the oil to dry completely between coats and to buff the final coat with a soft cloth. With proper care, the oil will provide a beautiful, durable finish that will last for years.

Common Uses of Tung Oil

Beyond its use as a wood finish for home woodworking shop projects, tung oil has other applications, including as a finish for boats and musical instruments.  It’s water-resistant, durable, and easy to apply. 

However, the oil has other uses, including:

• Metal finishing: It can also be used to finish metal. It can help to protect metal from corrosion and to give it a smooth, even finish.
• Leather finishing: It can also be used to finish leather. It can help to protect leather from moisture and to give it a soft, supple finish.
• Other uses: It can also be used for a variety of other purposes, such as:
  • Lubricating: It can be used as a lubricant for a variety of tools and equipment.
  • Waterproofing: It can be used to waterproof a variety of materials, such as wood, leather, and canvas.
  • Preservative: It can be used as a preservative for a variety of materials, such as wood, leather, and paper.
  • Cooking: It oil can be used as a cooking oil. It has a high smoke point and a mild flavor. We’ll admit we’ve never used it in the kitchen as cooking oil, but it is food safe.

Tung Oil Storage and Shelf Life

It’s a natural product, made from the seeds of the tung tree, and as you would expect, it can go bad.  Over time, and if not stored properly, the oil will oxidize and turn rancid just as other natural oils (olive, vegetable, canola, corn, linseed).

Once the oil has turned, it will take on that rancid smell, and you’ll know it when you smell it that it’s time to go to the hardware store for a new can.  Even when stored properly, tung oil’s shelf life is about 2 years.  It can be purchased in containers of various sizes, so if you don’t expect to be using a lot or have just a single project to use it on, purchasing a small container would make sense so as not to waste it.

How To Properly Store Tung Oil

To prevent tung oil from going bad, it is important to store it in a cool, dark place. The oil should also be kept in an airtight container. If it is stored properly, it can last for up to two years.

Here are some tips for storing tung oil:

• Store the oil in a cool, dark place.
• Keep the oil in an airtight container.
• Use the oil within two years of purchase.
• Since going rancid is caused by oxidation, removing oxygen from the container will help keep it fresh for its normal useful lifespan.  Adding clean pebbles to the container or squishing in the sides of the container to keep the oil topped off (and thus removing oxygen from the container) will slow down or prevent that from happening.
• Another trick is to use a gas other than oxygen, like Bloxygen, in the container.  Bloxygen, which is a play on “blocks oxygen”), can be purchased in a can with a spray tube; opening the lid of the container and spraying it in will force the oxygen out of the can, reducing or eliminating the chance for oxidation.  Bloxygen is ultra-pure, natural, inert argon gas.  It is safe to use, a natural part of the air we breathe, and it is used for the same purpose in foods, wines, and liquors.

If you are unsure whether or not tung oil has gone bad, you can test it by smelling it. Rancid tung oil will have a foul odor. If the oil smells rancid, it should not be used.

Video of Tung Oil In Action

Just a short video with a few tips on its use, and to see the oil being applied to wood.  It brings the wood to life and shows you how your project could turn out.

Keep it sealed tight, keep oxygen out of the container, and keep it in a cool, dark place, and your tung oil will last in your shop for a couple of years.  You will be able to tell by the smell if it has turned.