Linseed oil also called flaxseed oil, it is made of pressed flax seeds which are sometimes added by solvent extraction.
The oil is edible and can be used for various purposes such as nutritional supplement, traditional delicacy, a material to putty, paint binder, and wood finish. Among those purposes, the wood finish is the most common usage.
For those who are interested in using this oil, they might wonder: How to apply Linseed oil as the wood finish? Can you varnish over linseed oil? Here is the explanation.
Linseed oil is mainly used as a varnish because of its natural polymer-forming properties that can turn into a solid form.
Varnished Over oiled wood
Because varnish also has oil, you can put it on wood that has already been oiled.
Be careful when using varnishes made with water because they will ruin the oil finish.
If you want to put varnish on top of an oil finish, look for an oil-based varnish and read the directions to make sure it works with an oil finish.
Varnishes show through the oil finish underneath, so you may need to sand the wood to smooth out any rough spots before applying the varnish.
Those properties make the oil become the favorite natural drying oil.
The oil has several product types: edible flax oil, raw linseed oil, boiled linseed oil, polymerized linseed oil, double-boiled linseed oil, Danish oil, Tar oil, and sun-thickened linseed oil.
Linseed oil as varnish
As varnish, the frequently-used Linseed oil types are Tar oil, Danish oil, and boiled linseed oil. The original one was produced decades ago and used to be popular in woodworking.
Yet then it is replaced by synthetic alkyd resins. However, as the organic product trend emerges, linseed oil returns and joins the trend again.
The oil as the varnish brings out the color and is eco-friendly. Besides furniture, it is also applied as a wood finish for kitchen utensils or any wooden tools related to food.
Despite its great result, the oil as a finish sometimes causes wood to bleed oil and makes the wood susceptible to scratches and staining.
Adding more varnish might solve the problems, but is it necessary to varnish over linseed oil?
When put on wood, how long does linseed oil last?
Wood needs to be oiled every two to three years, depending on its use and location.
If the wood turns gray, you need to repaint it. If the wood looks dry or has changed color, you must add a thin coat of oil again.
Use linseed oil on the parts of the wood that will be seen. It is long-lasting and won’t get damaged by water.
Clean the wood with a damp cloth, let it dry completely, and then put oil on it. After 10 minutes, wipe off any excess oil.
Keep the surface clean of dust and dirt, or the oil won’t be able to get into the wood and protect it. Check the wood’s finish often to ensure it hasn’t been damaged.
Repeat this process every year or after a few years, depending on the wear of the finish.
Can you varnish over linseed oil?
The straight answer is yes. However, the best result will depend on several points. The first point is the type of linseed oil. Raw linseed oil takes more time to cure. Varnishing over uncured wood will only damage the result.
The second point is the type of varnish. Water-based varnish does do well over linseed oil since oil and water cannot be together. Instead, oil-based varnish can be good additional protection as varnish.
Linseed oil provides protection, allows the wood to retain moisture, and does not shrink.
Varnish coats wood with a hard surface, and linseed soaks into the wood’s pores.
Because it soaks into the wood so well, the natural surface of the wood is retained.
A varnish can be achieved with products or combinations of products that include polyurethanes, lacquers, epoxies, etc. In short, you CAN apply lacquer or polyurethane over a Linseed oil.
As you can over any Drying Oil, the key to success is ensuring the oil has fully dried first.
Advantages and disadvantages of Linseed oil
As mentioned before, some woodwork still needs varnish over linseed oil. Is it better to oil or varnish wood?
The varnish is more resistant to water, heat, solvents, or other chemicals than oil. It seals the surface. It also has a more glossy finish than oil.
The use of Linseed oil only as the wood finish has advantages and disadvantages as follows:
- Eco-friendly and non-toxic, which can be applied on kitchen utensils
- Helps to overcome color changes during fluctuating humidity
- Remove the dents and scratches easily by sanding them out
- Absorb to the wood grain bring out texture as well as the color
- Give a fast, long-lasting color change on woods
- Stimulate wood’s “blood” oil during changing temperature
- Prone to scratches, staining, and water rings
- Turn the wood yellow slightly through times
- Need regular re-oiling
Good and bad varnish over linseed oil
Oil-based varnish is best to apply over linseed oil. Examples of oil-based ones are Polyurethane, Varathane, Dewaxed Shellac, and Formby’s Tung oil.
Besides, paste varnish works well. Adding other linseed oil (Danish, boiled linseed oil, Tung oil) is also good.
The additional varnish usually serves as extra protection, and the ‘lense’ accentuates the look of the depth of the wood piece.
In contrast, lacquer is not compatible with linseed oil. For a safer option, boiled linseed oil is the alternative to be applied under the lacquer.
Then how about water-based? Can you varnish over linseed oil?
Certain types work well with boiled linseed oil as long as they dry quickly.
However, the order should be boiled linseed oil coated with water-based varnish. Not vice versa, or else the varnish will chip and flake.
How to apply varnish over linseed oil
After knowing the advantages of varnishing over linseed oil, the question of ‘can you varnish over linseed oil?’ might shift into ‘how to apply varnish over linseed?’. In detail, here are the steps.
- Sand the wood to 180 or 320. Then remove the dirt and dust. Make sure that there is no material on the surface.
- Wipe a light coat of the oil and let it cure.
- Then apply the heavy coat of the oil and again let it cure for days.
- Once the surface is cured perfectly, brush the chosen varnish.
- Please wait until it is cured based on the directions of each varnish.
- Finally, sand lightly when the surface is set to get the desired smooth surface and look.
The cured time of each oil and varnish is different and influenced by the temperature, humidity, airflow, and light.
Raw linseed oil usually takes up to ten weeks, and boiled linseed oil only requires four to six weeks.
Besides, you must be aware of the difference between cured and dried. Woodworkers might apply three or more varnish, but two coats are sufficient.
For each varnish, it is recommended to sand the surface first before applying the new coat.
Benefits of having varnish over linseed oil
While the linseed oil perfects the look, the oil does not protect the wood from water, heat, or alcohol. This is why some say linseed oil is safe for kitchen utensils but doesn’t perform well.
Kitchen utensils interact directly with moisture, heat, air blow, and pressure.
Hence varnish over linseed oil will do better. In addition, only applying an oil coat is still susceptible to scratches.
The extra varnish on top of the linseed oil makes the wood’s surface thicker, protecting it from dents and scratches.
Maintenance for the varnish over linseed oil
Through time the varnish could get thinner and disappear, so reapplying the varnish is needed.
Then, can you varnish over linseed oil and reapply it again? Sure, you can. Adding paste wax over the varnish yearly can be another alternative for special furniture.
For daily care, cleaning the light soil can be done using a damp cloth or by vacuuming. Just do not let the damp cloth stays too long on the surface.
Use a mineral-spirits-dampened cloth to remove wax build-up, then add paste wax.
Be careful with the dampened cloth in spirits and dispose of it following the directions stated on the label.
Frequently Asked Questions
Is it better to oil or varnish wood?
The varnish is stronger than oil against water, heat, solvents, and other chemicals. It seals the top.
Varnish is cheaper than oil and gives the wood a glossier finish. Varnish can also protect the wood from getting wet.
Oil can be put on wood to keep it from getting wet and make it look more expensive.
Oil will not last as long as varnish. If you do a lot of projects outside, you should use varnish instead of oil.
Use varnish on outdoor furniture and other things that will be in the weather.
Also, the varnish is easier to use than the varnish. oil requires multiple coats to cover. It only needs one coat of varnish.
Does oiled wood need to be sealed?
You can seal oiled wood to keep its original beauty, but there is no need to seal oiled wood.
But you should sand the wood very well, especially around the edges and corners, to ensure the surface is smooth and has no bumps.
Before applying the finish, thoroughly clean the piece of furniture with a tack cloth. Finish the entire piece of furniture with a thin coat of oil and allow the oil to dry completely
Can you mix linseed oil and varnish?
Materials like mineral spirits and boiling linseed oil can be purchased in bulk gallon containers, and varnish can be purchased as needed.
In addition to varnish, thinners such as mineral spirits, paint thinner, turpentine, or naptha, and tung oil or boiled linseed oil are also used in equal parts (poly, spar, etc..).
Alternatively, you may make a solution by mixing equal quantities of boiling linseed oil and turpentine.
How long does linseed oil take to cure?
Linseed oil creates an excellent finish for wood goods if applied in thin coatings and given plenty of time to cure.
However, depending on the environment and the thickness of the application, it might take anywhere from two weeks to ten weeks for the oil to completely dry out.
Is linseed oil a good finish for exterior wood?
Applying linseed oil to the exterior or any wood that will be exposed to the elements is not recommended.
Woodworkers utilize mineral oil because it has a low sheen and does not dry the wood.
On some cutting boards found in kitchens, food-safe wood oils are applied; these oils do not dry out, but they can be removed by washing the board.
What’s the difference between boiled and raw linseed oil?
Raw Linseed Oil has a drying period that is considerably longer than that of Boiled Linseed Oil, which has been processed by passing hot air through the liquid, significantly reducing the drying time of Boiled Linseed Oil.
This is the primary distinction between the two types of linseed oils.
When working with woods other than oak, it is suggested that you use boiled linseed oil instead.
What is the difference between linseed oil and Danish oil?
Linseed oil and Danish oil are two entirely different things.
Linseed oil is entirely natural from flax seeds, whereas Danish oil combines tung oil, linseed oil, and mineral spirits.
There are also differences among them in terms of their finishes, qualities, and applications, among other things.
What’s the difference between polyurethane and varnish?
While polyurethane is water-based and oil-based, the varnish is an older product manufactured from resins, oils, and solvents. Because of the greater solids ratio, the varnish is less vulnerable to UV radiation degradation.
Because of this protection, the varnish is a fantastic choice for outdoor decks and outdoor furniture projects.
Varnish is intended for outdoor projects and is not commonly used on indoor surfaces such as hardwood floors.