March 4, 2023
My client asked me the other day regarding the number of coats of tung oil he needed to apply to protect wood completely. I told him the number of coats would usually differ depending on the project’s requirements. If you coat decorative items, you can go up to four coats. Yet, if the surface is subjected to heavy usage, you can go up to five or more coats.
If you use boiled tung oil, on the other hand, it will be best to apply anywhere from four coats to six coats for complete and adequate surface coverage and durability. However, if you use raw tung oil, you only need to apply two coats for good coverage, for raw tung oil has a thicker consistency.
How To Know You Need to Apply Another Coat of Tung Oil?
You will never know if you must apply another tung oil coat if the previous coat has not yet dried. Once the last coat has dried, inspect the coat. You must apply another coat if it looks lighter than the desired color. Remember that the more tung oil coat you apply, the darker and deeper the finish will be.
Tung oil can penetrate the wood grain deeper than any wood finish. Wait until the existing coat is completely dried, and touch and rub the wood surfaces with your finger gently. If you can still feel the grain texture, you will need another coat of tung oil.
Tung oil, of course, penetrates deep into the wood fiber. Thus, if you notice that the wood texture is still visible or if you feel it, it only means that the previous coat has yet to go deep into the wood fibers.
Hence, you must apply another layer of tung oil to ensure maximum protection for the wood. The tung oil should form a protective layer over the wood surface for maximum protection.
You can also try the water test to determine if another coat is needed. The water test consists of pouring water over the tung-oil-coated surface of the wood. Then, wait for several minutes. If the droplets of water get absorbed by the wood, the finish is insufficient to provide protection from moisture and water. Hence, applying another tung oil coat for maximum protection will be best.
Nevertheless, if the water stays on the surface without being absorbed by the wood, you have provided the wood with enough coats of tung oil. However, you should only do this test once the tung oil has already dried. Lastly, it will help if you check the manufacturer’s instructions to determine the recommended number of coats of tung oil you should apply.
What If You Don’t Apply Sufficient Tung Oil Coats?
If the coats you’ve applied on the wood is not enough, you can never expect a strong finish that could provide sufficient protection against moisture, water, decay, and stains. Besides, the finish will appear lighter than expected and transparent. Moreover, it might seem streaky due to inadequate coverage and wood soaking.
Insufficient coats may also fail to provide enough protection for the wood, making the wood susceptible to damage due to moisture and water. Cracks and lines may appear over time, indicative of weak tung oil coats.
Tung oil can waterproof wood and provide it with an excellent finish. Yet, to achieve a fantastic finish, you need to apply at least four tung oil coats. Besides, to ensure the finish is water-resistant, you must apply at least four to six coats. Insufficient coverage and coats will lead to many issues and damage to wood afterward.
Factors to Consider When Applying Tung Oil
Tung oil can provide wood with a fantastic finish. It is also a natural finish which you would surely appreciate. Yet, when applying tung oil, you must remember several factors to achieve the best finish for your project.
First, you should remember that tung oil takes time to dry and cure. Moreover, you should apply it evenly. Furthermore, you should make additional applications to maintain the finish and natural looks of the finish. So, you must coat the tung oil finish once twice a year.
Another thing is that the tung oil finish is not without odor.
Nevertheless, its odor features a natural smell that is nutlike. Thus, it is not pungent to the nostrils.
Drying Time and Curing Time
As a beginner in woodworking, it will be best to know that drying and curing times are two different things. Yet, many would interchangeably use these two words. Drying time refers to the required time for each coat to dry. Curing, on the other hand, refers to the necessary time before you can use the project. Thus, drying time is shorter than curing time.
Tung oil coat can typically dry within 24 hours. But if it is pure tung oil, it may take up to 72 hours to dry completely before applying the next coat. This is because pure tung oil doesn’t contain dryers or additives that engender fast drying. Thus, it takes longer to dry completely.
However, to adequately dry, refined or boiled tung oil may take four to six hours. Thus, you must wait shorter before applying the next coat. Refined tung oil usually contains drying additives for fast drying.
Thus, when you apply tung oil, you need to wait for a maximum of one and a half hours for the wood to absorb the tung oil. Once the wood absorbs the first coat completely, you must wait another hour to let it dry before you can sand it using 400-grit sandpaper. Once the last coat has penetrated the wood entirely and hardened, you can apply the next coat.
If you apply the next coat earlier than the required time, moisture might get trapped between coats, causing the tung oil to get sticky. Besides, you might end up with a blurred and murky finish, characteristic of the work of beginners.
Factors Contributory to the Drying Time
Tung oil dries slowly compared to other finishes, especially if the oil is pure. However, the drying time of tung oil might be affected by several factors. Below are the factors that could influence the length of drying time of tung oil:
The weather condition can influence the length of drying time of tung oil. If the weather is humid or cold, the tung oil’s drying time might get longer. Remember that cold temperatures coupled with high humidity level make the tung oil dry slowly. So, ensure you apply tung oil during ideal weather conditions.
Amount of Tung Oil Applied
Another factor that could prolong the drying time of tung oil is overapplication. Tung oil may take longer to dry if you apply thick coats. Besides, if you use too much tung oil, you should wipe excesses off the wood surface.
Another factor is the ventilation of the room or shop where you apply tung oil. The area where you apply the tung oil should be well-ventilated with sufficient air circulation. Otherwise, the drying time might be prolonged.
How Long Would It Take the Tung Oil Finish to Cure?
The curing process differs depending on the type of tung oil you use. If it’s pure tung oil, it will take a month or forty-five days to cure, given optimal conditions. Nevertheless, if it’s polymerized, oil/varnish blend or wiping tung oils, they may take 2 – 4 days to cure.
Reasons abound why woodworkers love to use tung oil for their woodworking projects. One reason is that it is flexible and durable. Besides, it is food-safe and can provide your wood with a waterproof finish. Moreover, it can protect wood against mold and doesn’t darken over time.
Tung oil also dries faster than other types of oils. Thus, it will need less drying time compared to different oil finishes. Aesthetically, the tung oil finish provides an excellent finish to a project. As such, it is a perfect finish for many woodworking projects.
Liam is a 37-year-old woodworker and interior designer who loves to make every furniture project an art piece. He is very experienced in furniture design and woodworking project planning.