Tung oil is commonly used for its waterproofing and honey-tone finish on the wood. But, when it turns sticky, you don’t get any of these qualities. So how do you fix a sticky Tung oil finish?
To fix a sticky Tung oil, increase the air circulation and heat around the coating. This can be done using a fan and hairdryer. However, if it has dried in its tacky state, you must dissolve it with turpentine and wipe the excess off.
If you can’t fix it, you must remove the its finish, prep the surface properly, and re-apply it.
Why Does it Turn Sticky?
The usual cause of sticky Tung oil is unfavorable drying conditions. Tung oil is a natural wood oil finish that is very picky when it comes to its ideal drying conditions. It must be applied on a dry, sanded, and clean wood.
Asides from this, the room temperature needs to be between 50-90 degrees Fahrenheit, and humidity levels need to be below 40%. If you apply the wood oil without meeting any of these drying conditions, chances are it will turn sticky.
For instance, if it is applied to wet wood, the moisture in the wood will dampen it, causing it to remain wet and turn sticky. Also, if the humidity (level of moisture in the air) is more than 50%, the wood oil will not dry and will turn sticky.
Here are some other reasons:
1. You Apply Too Much of It
Tung oil needs many coats for proper coverage, protection, and durability on the surface. When working with raw Tung oil, you need at least 5 coats. When working with polymerized or heated Tung oil, you need at least 3-4 coats for a good finish. The reason for needing many coats is to allow the wood to fully absorb the wood oil.
Since many coats of are needed, it becomes easy to get carried away and over-apply it. When you over-apply the wood oil, there will be more oil on the wood than the wood can absorb. The excess that isn’t absorbed will remain on the wood surface and turn gummy or sticky.
2. You Applied Raw Tung Oil
Raw Tung oil contains no metalized dryers, quick-drying additives, or solvent which means that it dries very slowly. The Tung oil takes about 3 days to fully dry so if you applied raw Tung oil, this is the reason your finish is sticky. If you want a quick-drying finish, you should apply polymerized Tung oil finish.
Polymerized Tung oil finish contains metalized dryer additives and petroleum-based solvents like mineral spirits that make the finish dry in a few hours.
3. You Didn’t Wipe Off The Excess
Being a wood oil, Tung oil needs to be fully absorbed in the wood pores to stick and dry properly. However, it’s difficult to agree on a certain number of coats that will fill all types of wood pores.
Since the porosity of wood varies from different types of wood, manufacturers recommend applying several coats on a surface and waiting 30 minutes for the wood to absorb as much oil as it can.
After 30 minutes, the wood pores will be filled and you can wipe off the excess that is on the surface. If you don’t wipe off the excess, it will gunk up and turn sticky.
4. Sealed Surface
Tung oil needs to penetrate the wood to stick and dry. If the surface is sealed with polyurethane or any other sealant, the Tung oil will not be able to penetrate as it should because the wood pores would have been sealed by the sealant.
Since it can’t penetrate, it won’t stick and will not dry. Instead, it will stay on the sealed surface where it will gunk up and turn sticky.
5. Re-coated Too Soon
If you recoat Tung oil too soon, it will turn sticky. This is because there will be solvent trapped in the existing coat. The trapped solvent will dampen the next coating, causing it to stay wet and turn sticky after a few hours.
You must wait 2-4 hours between coats of polymerized or commercial Tung oil and 24-72 hours between coats of raw Tung oil. This is to give the coat enough time to dry and harden before a recoat.
If you recoat the Tung oil too soon, solvent (or oils) will still be present in the first coat, and recoating too soon means you’ll trap the solvent between the first and second coat. This will stop either coat from drying and after a while, the finish will turn sticky.
Will Tacky Tung Oil Eventually Dry?
If the wood oil stays tacky after 24 hours, it will not dry unless you applied is raw Tung oil. If the Tung oil is raw, it can stay tacky for up to 3 days and still dry eventually.
But, for polymerized and commercial Tung oil finishes, it will not dry if it stays tacky after 24 hours. In this case, you’ll need to fix the cause of the stickiness and leave it to dry.
Ordinarily, polymerized Tung oil takes 12 hours to dry but can stay sticky for up to 24 hours before it dries especially if it was applied in a moist or cold environment. If it remains tacky after 24 hours, it will not dry.
If the maximum dry time has passed and the wood oil is still tacky, it will not dry itself. In this case, you’ll need to find the cause of the stickiness and fix it to allow it to dry.
How To Fix Sticky Tung Oil?
To fix a sticky finish, you must find the cause and fix it. For instance, if you applied the wood oil over a wet surface, you must remove the finish, dry out the surface, and re-apply it.
Here are some fixes you can try:
1. Use A Hairdryer
Tung oil dries based on evaporation or heat and it cures based on oxidization or air current. So, if you expose the sticky (or non-drying) coating to heat from a hairdryer and air current from fans, it will dry and cure faster.
This method should be used within 24 hours of applying it. If the sticky coating is allowed to solidify in its sticky state, this method will not work.
For this method, you need these:
- A hairdryer
- A pair of gloves
- A face mask
Here is a guide for this method:
- Tap the coating with your fingers to know the wet and sticky parts.
- Plug-in and turn on the hairdryer.
- Set the heat to medium.
- Move the hairdryer around the sticky parts of the coating for 5 minutes (do this at an interval of 15 minutes for an hour).
- Turn on the fans in the room and direct them to the sticky coating.
- Turn off the hairdryer but leave the fans on as long as possible.
- Leave the coating to dry and cure manually.
Tip: Do not over-use the hairdryer because doing so can cause the finish to dry on the surface but remain wet underneath.
2. Dissolve and Wipe Off The Excess
This method works for tacky Tung oil that has solidified in its tacky state. If the maximum dry time has passed and the coating remains tacky, this is the method to fix it. Also, if the tackiness is caused by the excess application, this is the fix to use.
The idea here is to dissolve the tacky Tung oil with mineral spirits and when the oil is dissolved, you can wipe it with a clean rag. This will reduce the amount of it on the wood and allow the surface to dry normally.
For this method, you’ll need these:
- Mineral spirits or turpentine
- Clean rags
- Plastic bags
- A pair of gloves
- A face mask
- A natural-bristled paintbrush
- Polymerized Tung oil
Here is a guide for this method:
- Pour some mineral spirits or turpentine into a clean bowl. You can also use 90% acetone for this but be careful because acetone can remove the entire finish.
- Soak a rag in the solvent.
- Sprinkle some of the mineral spirits directly over the sticky parts of the finish.
- Leave the coating to absorb the mineral spirits for 30 minutes.
- Use the damp rag to wipe off the excess.
- Swipe across the wood surface in the direction of the wood grain twice to remove the excess.
- Touch up the coating by applying a light coat of polymerized Tung oil.
- Wipe again and leave the surface to dry.
3. Remove The Sticky Finish
If nothing works, then remove the sticky finish, fix the cause (problem), and re-apply it. This method works for sticky finishes that have been contaminated by stains, filth, and water. In this case, you can’t restore it, so the best option is to remove it.
Here are three ways how to do it:
- Strip the finish with a solvent-based paint stripper.
- Sand it off of the wood with sandpaper, sanding block, or sanding pad.
- Use acetone and steel wool to dissolve and remove it.
Tung Oil Has Cured If:
Here are expert signs that indicate when the wood oil has cured:
- If it is waterproof – Tung oil only becomes fully waterproof when the oil has cured.
- If it has a honey-like tone on the wood – This tone only shows when the oil has cured.
- When it’s no longer sticky or gummy.
- When it’s hard and durable – Tung oil only reaches its peak strength and durability when the oil has cured.
Preventing it From Turning Sticky
- Leave enough dry time between coats.
- Always follow the manufacturer’s instructions when applying it.
- Apply it only in optimal drying conditions.
- Wipe off the excess after application.
- Wipe, clean, and sand the wood before applying it.
In summary, Tung oil turns sticky for many reasons but the issue can be fixed. You just need to find out the cause of the stickiness and take the right step from those discussed in this article to fix it.
You should know that preventing it from turning sticky is better than finding a fix for it when it turns sticky. So, always follow the manufacturer’s instructions and leave enough dry time between coats.