One of the most common natural finishes is tung oil, an extract from the tung tree nuts. It outperforms other oils in durability, water resistance, and hardness. The properties of tung oil make it a good choice for kitchen use, but you might be wondering: is tung oil really safe for food? Read on to learn more about tung oil considerations and what you need to do, and in this article, you’ll learn what tung oil finishes really mean.
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What Is Tung Oil Made Of?
Tung oil is a natural oil because it is ground from the seeds of the tung tree. This oil is 100% pure and does not contain any hidden additives or chemical drying agents.
However, tung tree seeds are incredibly toxic. Likewise, the oil extracted from it is also unfit for human consumption.
How Toxic Is Tung Oil? Can It Make You Sick?
Yes, it can. That’s because pure tung oil is toxic in its stock form. So, you don’t want it to get into your food in any form.
Also, not all tung oil products on the market are even tung oil. Many of them market themselves as such. However, unless the label specifically states “100% pure tung oil”, this wood finish is likely not at all.
You see, these fake tung oil products are more like teak oil in their makeup. They contain a mixture of natural oils, chemical thinners, varnishes, and other additives. Some may contain a little tung oil. Others may not.
The liquid form of these fake tung oil products is also toxic. That’s why you should make sure they never end up on your dinner plate.
Different Tung Oil Finishes and Their Food-Safety
There are three different types of penetrating tung oil finishes. All of these may be labeled as tung oil, but they differ in composition, and some of them are better suited for wood in a kitchen or children’s room.
The most common types are pure tung oil, tung oil-based wipe varnishes, and oil/varnish mixtures. However, some manufacturers may not use these terms on the label and simply refer to their product as tung oil. You can tell them apart by reading the ingredient list or its safety sheet.
Pure Tung Oil
Identification of pure tung oil is easy because it has no solvents, which means there is little chance of exposure to volatile organic compounds (VOCs). Therefore, natural tung oil is harmless and can be used where food safety is required. This is also
One downside of this oil, however, is the tedious application process. To get a strong protective film, several coats are required (some recommend five or more). It may also take a few days to harden completely.
Its application also requires some skill and experience. Thick coats can cause wrinkling. In this case, you have to hard sand it to get a smooth finish.
In any case, you will need to repolish the wood regularly to maintain protection and enhanced appearance.
On the other hand, oil/varnish mixtures and wipe varnishes are enhanced with chemicals to simplify the application process and improve drying time and the durability of the topcoat.
According to the U.S. Food and Drug Administration (FDA), tung oil is generally considered food safe (source). However, its use in food packaging requires a no-objection letter from the FDA (source).
Oil/Varnish Mix
These tung oil blends consist of a mixture of tung oil and a solvent such as mineral spirits. They were developed to make application easier and to speed up drying times. You’ll know it’s an oil/varnish mix once you see “contains petroleum distillates” on the label.
While this increases the ease of its application, it also means that care should be taken when applying it to areas that come into contact with food. Once fully cured, it is generally considered food-safe under the FDA’s Code of Federal Regulations.
During curing, it may evaporate smelly or even unhealthy fumes, depending on the type of solvent used as an ingredient. Therefore, please follow the instructions on the back of the can during the recommended curing time. You can add a few more days to be safe.
Wipe Varnish
Rubbing varnish is an oil-based topcoat made from mineral oil, soybean, linseed, or tung oil and cooked with resin. Compared to pure tung oil, it has the advantage of faster drying time, greater resistance, and easier application. These varnishes contain a thinner that can be wiped off with a cloth, so they are called wipe varnishes (source).
While the product may be labeled “tung oil finish” or similar, you can tell if it’s a varnish by checking the ingredients: if it also contains petroleum distillates, it’s a wiping varnish, not pure tung oil.
Similar to other oil/varnish mixtures, wipe varnish is safe after it has fully hardened. However, during the oxidation process, hydrocarbons and aldehydes are released in very low concentrations that, although low, do not pose a significant health risk to healthy individuals. However, for people with allergies or serious pre-existing conditions, this can be considered unpleasant or even dangerous.
Which Tung Oil Finish Should You Choose Considering Food Safety?
While there is no doubt that tung oil is toxic (source), tung oil itself is also non-toxic. The FDA has approved the use of pure tung oil finishes on surfaces that come into contact with food, including dining tables, furniture, cutting boards, etc.
However, in rare cases, unhardened tung oil may cause an allergic reaction. Therefore, wood treated with tung oil can only come into contact with food after it has completely dried.
Tung oil is usually diluted with a solvent during the application or as a ready-made varnish. While fully cured is still food safe, it is more important to allow adequate drying time and to store treated objects away from food and children (such as in a workshop). Depending on the solvents used in such mixtures, odors and unhealthy fumes may develop during curing.
There are many things you should consider before making a decision before choosing a specific type of varnish. This includes:
- FDA Food Safety Assessment of Cured/Hard Surfaces
- its curing time, and
- Health risks during application and curing.
Using pure tung oil without any solvents should be the “safest food” way to finish wood with tung oil. However, the application of undiluted tung oil is quite heavy and may affect appearance and require longer drying times. This is why oil/varnish mixes and rub varnishes have become popular over the years, however, they are only food safe when fully dried or cured.
However, there are other food-safe wood finishes that you may want to consider.
Conclusion
Tung oil is a food-safe wood finish that can be used in kitchens and children’s rooms. However, it should have cured properly, which is more important when mixing with solvents or using oil/varnish mixtures. When it comes to food safety, using pure tung oil may be your best bet. However, it can be difficult to apply without solvent, which can add unhealthy ingredients to the mix.