A coat of varnish over furniture offers the best protection to the wood grain from moisture and scratches. But can you use varnish over oiled wood?
You can put a coat or two of oil-based varnish over oiled wood as long as the oiled wood is fully dry. Since oil-based varnishes contain high amounts of oils, the varnish is compatible with wood oil.
You should know that it’s not advised to apply a water-based varnish over oiled wood. This is because water-based varnishes have a high amount of water and not oils. As such, the water-based varnish is not compatible with wood oil.
You should also know that sanding the oiled wood with fine-grit sandpaper helps the varnish to stick better. The varnish needs to stick so the finish can be strong. So, does varnish stick to oiled wood? Let’s find out.
Does Varnish Stick To Oiled Wood?
Ordinarily, varnish doesn’t stick well to oiled wood. This is because oiled wood tends to accumulate dust over time that can prevent the varnish from sticking properly.
Also, most wood oils dry hard meaning that the varnish can’t penetrate or soak into the wood. Since the varnish can’t soak into the oiled wood, it won’t stick properly.
However, you can make varnish stick better to oiled wood if you sand the oiled wood first. When you sand the oiled wood, you’ll create pores in the oiled wood that the varnish can bite into giving the varnish improved adhesion and bonding. Also, if you sand the oiled wood, the abrasive side of the sandpaper will remove dust and grain in the wood oil to make the varnish stick better too.
Oil-based varnish sticks better to oiled wood than water-based varnish. In most cases, the water-based varnish will not stick to oiled wood because it’s not compatible with wood oil. Oil-based varnish however sticks better but it’s advised to sand before applying the varnish.
Related Read: Varnish vs Wood Oil
Can You Varnish Over Oiled Wood Without Sanding?
You shouldn’t varnish over oiled wood without sanding. This is because the varnish will not stick to the oiled wood if you don’t sand.
Wood oils like Linseed oil are known to penetrate deeply when used on wood. Varnishes also have the same features, varnishes contain oils that also need to penetrate to stick. Since the oil on the wood has already soaked into the wood, the varnish can’t soak in too except you sand some of the wood oil off.
When you sand some of the wood oil off, you will create pores and spaces in the oiled wood for the varnish to soak into. This makes sanding compulsory unless you don’t want the varnish to stick.
Asides from the improved adhesion, sanding also helps to smoothen the wood oil so the varnish can come out even. Wood oils take a while to fully cure. During this period, the wood oil isn’t as hard as it should be so dust nibs and grains easily stick to the wood oil. When the wood oil dries fully, these dust nibs become pimples and bumps that you’ll need to sand off before you can varnish over the wood oil.
You are only allowed to use varnish over oiled wood without sanding if the varnish doesn’t need to penetrate the oiled wood. Acrylic varnish for instance doesn’t penetrate as much as other varnishes because it’s water-based. So you can try it over oiled wood without sanding but you should know that the finish would be far from perfect.
How Long To Wait Before Putting Varnish Over Oiled Wood?
You should wait till the oiled wood cures before you put varnish over it. On average, this takes about 3 days but you should know that thin wood oils like Tung oil cure quickly and usually within 24 hours.
So you can varnish over such wood oils sooner. On the flip side, some wood oils like Linseed oil take longer to dry and can take about a week to fully cure. So you’ll have to wait longer before you can varnish over such wood oils.
The bottom line is to wait until the wood oil has cured before you put varnish over it. How long this takes depends on the type of wood oil and the environmental conditions. If you varnish over wood oil before it has cured, the finish will be messy, cloudy, and very sticky. You will also battle strong paint fumes in the air.
Now that you know how long to wait before varnishing over oiled wood, let’s check out how to carry out the task.
How To Varnish Over Oiled Wood?
To varnish over oiled wood, you’ll need the following tools and supplies:
- Clean rags
- Paint scraper
- Paintbrush or spray gun
- Paint thinner (optional)
Here is a 5-step guide on how to varnish over oiled wood:
1. Scrape The Oiled Wood
The first step is to scrape the oiled wood. This step helps to remove some of the oils in the wood so the varnish can stick better. This step also helps to create pores in the oiled wood that the varnish can bite into.
Remember, you are not removing the wood oil. You just want to remove enough of it to give the varnish a fighting chance at sticking.
You can use a paint scraper or a putty knife to remove as much wood oil as you can. After scraping the wood oil, you are sure to have a very rough surface which brings us to our next step.
2. Sand The Oiled Wood
This step is to smoothen the wood after scraping. You should start sanding with medium-grit sandpaper. This will help to remove gouges and wood oil spikes in the wood.
After sanding with medium-grit sandpaper, you can sand with fine-grit sandpaper to even out grain and smoothen the wood. Don’t over-sand the wood or you’ll create holes in the wood that will suck the varnish and cause inconsistency.
While sanding, you should pay attention to the stress areas on the oiled wood. The stress areas are the parts that will be bumped into and used regularly. For instance, on a table, the stress area will be the tabletop and the edges. These are the parts where the varnish can come off quickly so you need to sand well so the varnish can have better adhesion and better resistance to chipping or peeling off.
After sanding, wipe the wood clean with a clean rag. Remove dust nibs, grain, and dirt from the surface.
3. Thin The Varnish
This step is optional but varnish is thick as it contains oils so it can be difficult to apply or spray without thinning it. To thin water-based varnish, use water.
To thin oil-based varnish, you can use paint thinner, mineral spirits, or lacquer thinner. You can thin the vanish up to 50%. Don’t over-thin as this will cause runs and drips.
4. Apply Varnish
Since the wood is clean and smooth and the varnish has been thinned, you can now apply the varnish. I’ll recommend using a spray gun to varnish over oiled wood as spraying helps with better coverage.
Asides from that, spraying help the varnish soak better into the oiled wood. If you decide to spray the varnish, then the previous step is no longer optional but compulsory.
You need to thin the varnish if you want to spray it as varnish in its original state is too thick to come out of the nozzle of the spray gun. So you’ll need to get the varnish thinner. While spraying the varnish, leave at least 8 inches between the nozzle and the wood to prevent splashes and stains. Also, use a spray shield to prevent overspray.
You can apply up to 3 coats of varnish but know that each additional coat of varnish makes the finish glossier and this will also enhance the paint color.
Ensure to allow each coat of varnish to dry. If you re-coat too soon, the finish will get muddled up. After applying the varnish over the oiled wood, leave it to dry for at least 3 days before subjecting it to regular use. You can also apply varnish with a roller.
Different Types of Wood Oil You Can Varnish Over
Here are some different types of wood oils, let’s check if you can varnish over:
You can apply varnish over Danish oil but you should know that Danish oil is a penetrating oil finish meaning that it fully soaks into the wood grain. So if you are to apply varnish over Danish oil, it’s best to pick a varnish that doesn’t penetrate too deeply.
Oil-based varnish for instance penetrates wood deeply too. So, if you put oil-based varnish over Danish oil, chances are the oil-based varnish wouldn’t stick well since it wouldn’t penetrate the Danish oil.
It’s better to use water-based varnish over Danish oil as water-based varnish doesn’t penetrate as deeply as oil-based varnish.
You can varnish over linseed oil but it’s better to use an oil-based varnish as oil-based paints generally do well over linseed oil.
You should know that linseed oil takes very long to dry so you need to ensure that the linseed oil has fully dried before you put varnish over it. On average, it takes boiled linseed oil less than a week to fully dry. Raw linseed oil can take several weeks.
You shouldn’t apply varnish over Teak oil. Teak oil is a natural oil that dries very hard. It would be almost impossible for varnish to penetrate or even stick to Teak oil.
To put varnish over Teak oil, you’ll have to strip or remove part of the Teak oil. With proper prep, water-based and oil-based varnish can stay on Teak Oil.
You can put varnish over Tung oil because Tung oil is compatible with several types of varnishes. Spar varnish especially works well over Tung oil but ensure to sand first. Also, ensure the Tung oil has fully cured before varnish.
You can varnish over Osmo oil if you use an oil-based varnish and sand the Osmo oil properly before varnishing. But you should know that it’s not advised to do so.
This is because Osmo oil is a hard wax finish and as such wouldn’t take varnish properly. It’s better to apply Osmo oil over varnish than the other way around.
Related Read: Can You Stain Over Wood Oils?
Can You Mix Varnish With Wood Oil?
You can mix varnish with wood oil but you can only mix oil-based varnish with wood oil. Never mix a water-based varnish with wood oil as the water in the water-based varnish will make it incompatible with the wood oil.
Mixing an oil-based varnish with wood oil creates an oil-based finish with improved durability and water resistance. The finish will also be extra glossy and reflective.
But there is a downside. While mixing wood oil and oil-based varnish creates a super durable finish, the finish will have a very high oil content meaning that the finish will turn yellow very quickly. Also, mixing both finishes will create a finish that will be super thick and difficult to control.
Overall, you can varnish over wood oil but you’ll need to ensure proper prep work to allow the varnish to stick as wood oils are usually resistant to a top coat.
Penetrating wood oils should be stripped or removed to allow the varnish to steak. You should also remember that oil-based varnish is more ideal on wood oils than water-based varnish.