Epoxy Over Linseed Oil? Does It Work?

Linseed oil provides a great non-toxic way of finishing wood in a semi-permanent coat that increases water resistance and durability of wood by soaking it at depth. However, the coat can wear out after a while and is by no means 100% waterproof. The first time I used linseed oil over a project, I had to go back and use epoxy to make the finish more permanent. Here’s what I found.

Epoxy can be used over linseed oil once the oil is fully dry. It works just as well as pouring epoxy over dry wood. However, it is redundant and unnecessary to apply a layer of linseed oil under epoxy when the overall project isn’t any more durable or better looking due to the oil.

Whether you have a piece of oiled wood you want to epoxy or you have yet to apply an oil finish to your project, this article will clear all misconceptions regarding the subject. By the end, you will know how to judge oiled wood to conclude if it is ready for epoxy, what happens when you pour epoxy over oiled wood and the best oil treatments for pre-epoxy wood.

Can You Epoxy Over Oiled Wood?

You can epoxy over oiled wood to a varying degree of success depending on the dryness of the oil finish. Dry finishes, once fully cured, allow the epoxy to grab onto the texture of the wood but thicker coats that create an impermeable layer between the wood and epoxy destabilize the adhesion.

Epoxy can stick to wood, and it can stick to solidified oil. However, its adhesion to oil is quite poor, which is why you must be careful using epoxy over oiled wood. First, you must inspect the extent to which the oil is noticeable. 

A neighbor put this out on bulk trash day so of course I brought it home. Spent the week sanding it, a little epoxy work, linseed oil, and a few coats of spar urethane. New cushion and wax arrive next week! 🛷 ❄️ pic.twitter.com/2N1cufJBxp

— Matthew K. Pelkey 🇺🇦 (@MatthewPelkey) January 30, 2021

Next, you have to look for the oil’s effect on the wood’s texture. After ensuring that the epoxy can access wood without being blocked by oil, you can proceed to epoxy over wood. The table below covers a set of possibilities.

Appearance	Texture	Can You Epoxy Over The Surface?
Glossy	Smooth	No. The layer of epoxy will not bond to the underlying wood.
Glossy	Rough	Yes. There is a thin film of oil coating the wood, but it isn’t blocking crevasses that epoxy can fill for better anchoring.
Natural	Smooth	No. The oil finish might have a matte effect, but it has compromised the wood grain required. You might need to sand it before epoxying it over.
Natural	Rough	Yes. The dry finish used over the wood has properly oxidized, leaving wood conducive to epoxy adhesion.

With the information covered in the table above, the following steps are the most obvious route to safely epoxying over oiled wood:

1. Step 1 – Look at the surface in bright light to check if it is glossy. 
2. Step 2 – Gently run your finger over the surface to assess its graininess.
3. Step 3 – If there is sufficient grain and little to no gloss, you can use epoxy on it.

The video below covers the results you can expect when applying epoxy over oiled wood.

https://www.youtube.com/watch?v=Cp1gz7xyXXg&ab_channel=SystemThree

What Happens When You Epoxy Over Oiled Wood?

Pouring epoxy over oiled wood can prove disastrous for your project if you are not careful. You have to be mindful of two things: the thickness of the finish and how well it has cured.

If the oil finish has not cured properly, here are the consequences you can expect:

• The epoxy layer separates from the wood – Uncured stain or oil finish can simply form an impermeable film over which the epoxy cures. Since the epoxy doesn’t firmly anchor into the wood, it separates as a dry layer. 
• There are bubbles and crates in the epoxy – When some of the oil has cured and the other parts of the finish/stain haven’t, the less dry areas repel the epoxy, creating craters where the epoxy doesn’t cure. The dry areas end up with more epoxy and sometimes have bubbles.

The best solution is to use drying oil and wait seven days after applying the oil finish or stain before you start your epoxy project. If the layer is too thick, you might even need to sand the surface.

Can You Seal Over Linseed Oil?

You can seal over linseed oil once the oil is fully dry. Waiting 96 hours (to one week) before sealing the oiled wood is the safest way to waterproof wood without destabilizing its finish. That said, you can also directly seal wood without applying linseed oil.

There is no need for oil if the sealer improves the wood’s finish and durability. Since all sealers are not built alike, one cannot say an oil finish is useless if one intends to use a sealer later on. The oil finish can introduce an interesting appearance and improve wood’s durability, while the sealer makes it waterproof. 

So, there’s room for debate when using different sealers over linseed oil. But when it comes to using epoxy sealer (or any sealer that also improves wood’s durability), linseed oil is completely redundant.

What type of finish do we use on Railcar and Cargo planks to seal them?-We use Poly Lacquer mostly but have used Paste wax, Tongue oil, and Linseed Oil, and on occasion, floated Epoxy. https://t.co/JF90UUqmyG pic.twitter.com/WdnVfUwua5

— Reclaimedwoods (@reclaimedwoodso) January 2, 2022

Do You Oil the Wood Before Epoxy?

You don’t need to oil the wood before epoxy because the oil does not present any advantages that are missing from epoxy. From water resistance to improved durability, everything that the oil is supposed to do is done better by epoxy.

One must look at epoxying over linseed oil from the perspective of risks and advantages. The table below shows why it is not worth it to apply linseed oil on wood before sealing it.

Advantages Of Using Epoxy To Seal The Wood (with or without linseed oil)	Disadvantages Of Using Oil And Then Epoxy Sealer
Makes the surface waterproof	Costs more because you pay for the linseed oil
Makes the wood scratch-resistance	There is a small chance the oil will interfere with the epoxy adhesion (if you don’t wait long enough before sealing).
Adds an interesting gloss to the surfaceCan turn the wood yellowish Table showing advantages and disadvantages of using epoxy over linseed oil

In conclusion, there is no exclusive advantage to using oil before epoxying a piece of wood.

All the advantages that apply to using epoxy after applying oil are also advantages that are valid when just using wood. This is like purchasing two “all you can eat” buffet slots for a single person. You spend more money but get the advantages of one.

What Oil Do You Use for Epoxy Resin?

You don’t have to use any oil for epoxy resin but can use any dry finish oil, including but not limited to linseed oil, tung oil, and castor oil. One can also use silicone oil to create permanent cells in epoxy art. Epoxy resin is mixed with a hardener, not an oil.

Instead of looking for the perfect oil, you must get a container of Premium ACS Grade Acetone, which can be used to clean wood 15 minutes before an epoxy pour. As long as a wooden surface is clean and prepped for epoxy, you do not need to oil it.

This video shows how you can do your epoxy pour.

https://www.youtube.com/watch?v=NL3ejW72DLY

Final Thoughts – Will Epoxy Stick To Linseed Oil

If you have a wood project that has been treated with linseed oil, you can wait 96 hours (or a week to be safe), then pour epoxy over it.

The oil is a dry finish variety and will not interfere with epoxy. But if the project hasn’t been treated with linseed oil and you intend to use epoxy over it, you can skip applying linseed oil altogether and simply use acetone to clean the wood.