MDF or medium density fibre is a very inexpensive material that is often used for furniture that is on the cheaper end. It is dense, durable, and very often very cost-effective for projects. Though one major flaw in MDF is that it is very weak against moisture damage. It absorbs water like a sponge, which makes it hard to use a water-based finish on it. Instead, an oil finish will help strengthen MDF and make it slightly more water-repellent. However, not all oil finishes are a great choice for it either. Don’t worry though, we did all the hard work for you and explored what kind of oil is best for MDF.
Pure tung oil and Osmo Polyx Hard-Wax Oil are the best products for finishing your MDF. Pure tung oil is a great choice because while it gets absorbed by the MDF, it does not damage or swell it. While it does take a huge amount of time to dry and cure properly, once it does, it will increase the durability of MDF and give it a little water-repellency. On the other hand, the OSMO Polyx Hard-Wax Oil contains vegetable oils that get absorbed by the MDF while the wax hardens on top giving it a nice smooth finish that helps water resistance.
MDF is an engineered board that is made out of shredded wood fibres. These fibres are then glued together and pressed tightly to create a board. While these fibres are made out of wood, they don’t have any properties of the wood they might be made of. So even if they were made out of a completely water-proof or water-resistant wood, the MDF board will still take water damage. So, most of the time these MDF boards are covered with a wood veneer or laminate. These protect MDF from water to a degree, laminate does so more than veneer. Though people finish off the veneer with a varnish or polyurethane that can create a film finish to prevent water from being absorbed by MDF.
Best Oils for MDF
1. Tung Oil
Pure tung oil or raw tung oil is one of the best finishes for wood, as it has proven to strengthen wood from the inside, making it durable, strengthening its fibres as it dries and hardens, and making it water-resistant. While MDF isn’t wood, tung oil also does the same for it too. The tung oil gets absorbed deep into the board and as it dries it hardens. Unlike water-based varnishes or polyurethane, it does not cause the MDF to swell up. Not to mention, natural tung oil is non-toxic and does not contain VOCs, so even if you dried and cured it inside the house, it would not harm the family.
On the other hand, tung oil takes very long to dry when used on MDF. It can take up to 24-48 hours to dry and more than 2 weeks to cure properly. So this is something to keep in mind when using something like tung oil for MDF. Not to mention tung oil has a strong odour, which is not harmful but not very pleasant either. Which makes finishing MDF inside the house a bit difficult.
After trying to find the best tung oil finishes that are natural and pure, Hope’s 100% Natural Tung oil is the best one we have come across so far.
2. OSMO Polyx Hard-Wax Oil
While a pure and natural finish is the best course of action for any wood, for MDF that might not be the case. Using boiled linseed oil on MDF is not the best course of action. Instead, the OSMO Polyx Hard-Wax Oil is a great product that while being natural is also great for engineered boards like MDF. Not to mention it is also a great oil finish for plywood too. OSMO Polyx Hard-Wax Oil contains vegetable oils like sunflower, soy, and thistle oil. These are not usually used as a finish by themselves, but here they have been processed in a way that they become drying oils.
The carnauba wax in the OSMO Polyx Hard-Wax Oil is the best part as it seals the MDF from the outside. It creates a hardened layer of wax that is very durable and prevents water from entering MDF. It creates a thin layer that does not allow water to enter the board sealing it completely. Just make sure to use a few coats as it will only improve the water-resistance of the engineered board.
Step-by-Step Guide on Oiling MDF
To apply oil to your MDF you need to prepare it just like any other wood. You need to sand it first and then apply your oil finish as it can help adhere the finish better. However, you can’t sand it like you normally sand wood. You need to sand it with a finer grit of sandpaper. This is because if you use coarse sandpaper, it will tear the fibres from the board instead of smoothening it.
Step 1 – Sanding the MDF
Since we are not dealing with a grain direction or pattern, you can go ahead and use a random orbit sander for this job. Though you will want to start sanding at around 320-grits instead of a coarser grit. As we said before, you shouldn’t sand MDF or particle boards with coarse grit sandpaper as it will tear fibres instead of smoothing the surface. Also, you don’t need to move up the grits as you do normally with wood. You just need to thoroughly sand with the 320-grits sandpaper. You can move to finer grit sandpaper but it is unnecessary as the oil will be absorbed by the MDF.
Step 2 – Oiling the MDF
Clean the board using a clean rag or cloth, make sure it is dry though. After cleaning, pour some oil on another clean rag and just apply the oil using that. Spread the oil evenly throughout the whole surface of the MDF board. Just make sure you don’t overpour as MDF absorbs liquids very easily. Also, ensure that you oil the corners and the sides of the board too.
Step 3 – Applying Another Layer
When you are finished with the first coat, wipe off the excess oil from the top of the MDF using a clean cloth. Let it dry overnight or for a whole day so that you can apply another coat of oil. Repeat the same process as before, pour some oil on a rag and wipe the oil across the surface of the board making sure that it is covered.
Step 4 – Curing
Depending on the oil that you have used on the MDF for finishing it, it can take from either a week to two weeks to cure. After you are satisfied with the number of coats you have applied, just wipe off any excess and leave the board to cure. Once it cures it will harden and protect the MDF from moisture damage and strengthen it.
Benefits of Oiling MDF
As we said before, MDF acts like a sponge for liquid, it absorbs water very readily. This can cause it to swell up so it is very hard to protect it without sealing it. Most sealers and finishes have water as a base, which works well for normal wood. However, in MDF it has the opposite effect as all the water is absorbed by the board too quickly. The water does not dry instead it is absorbed so the resins and chemicals do not cure properly.
An oil finish, though, does not act this way, as it does get absorbed by the board, but it will also harden and cure properly in its time. So oiling MDF is pretty beneficial in this regard. Not to mention it also helps make the board a bit more water-resistant, and the MDF also has a nice smooth feel to the touch.
FAQs – Frequently Asked Questions
Can I use linseed oil on MDF?
Yes, you can use boiled linseed oil on MDF, however, it will take too long to dry, as linseed oil already takes a lot of time to dry on normal wood. It will take twice as long to cure, this makes it an impractical oil finish for MDF.
Can you seal MDF with oil?
Yes, if you use the OSMO Polyx Hard-Wax Oil, you can seal the MDF with the wax added to the finish. Pure tung oil though will not seal MDF, you will still need to apply a clear coat finish on top of it to make it water-proof.
What is the best finish for an MDF workbench?
The best finish for an MDF workbench is an oil-based varnish. Since water-based finishes do not cure and work properly on a fibre board like MDF, the best course of action is to use something with oil as the base. You can also use tung oil and OSMO Polyx Hard-Wax Oil as they will nicely finish the MDF board.
People are hesitant to use MDF for projects since they feel it is a weak material. The truth is that these days most IKEA and reasonably priced furniture is made from this material. Also, it is pretty dense and does not break very easily as well. So knowing how to finish it with oil is only going to help in restoring old furniture that might have been damaged or needs a fresh look.