To make boiled linseed oil lighter, the finish must be exposed to dry and hot air. But, how many coats of boiled linseed oil do you need?
You must apply 3 light coats of boiled linseed oil. The first coat soaks into the wood and forms a substrate layer. The next two coats aren’t absorbed as much but stay on top of the surface where the finish becomes hard.
While 3 coats are the standard, you might need fewer or more coats depending on the brand of linseed oil, surface type, and the finish type you want.
Maximum and Minimum Coats
The maximum number of coats of boiled linseed oil is 4. You shouldn’t apply more than 4 coats. It’s recommended to apply only 3 coats, but if you are working with porous hardwood, you can apply 4.
If you apply 5 coats it will become difficult to control and protect the finish from contaminants while it dries. The finish will take longer to dry as you must wait longer for each coat to dry before applying the next one. The finish will also turn sticky.
Boiled linseed oil penetrates wood deeply when applied. The first, and in some cases the second coat, is absorbed deep into the wood fibers. When the wood has absorbed as much Linseed oil as it can, the absorbed oil dries to form the substrate layer. Then, you must two more coats to form the top coat. This is why 4 coats are the maximum.
If you use too many, the finish will take longer to dry. This is because there will be too more wood oil on the surface than it can be absorbed. In extreme cases, the finish will not dry and will turn sticky. When this happens, dust nibs and filth will settle on the sticky boiled linseed oil making it turn dark.
The minimum number of coats for boiled linseed oil is 2. That’s because the first coat will be absorbed into the wood, so you need another coat to form a layer over the wood.
If you apply only 1 coat of it, the finish will be weak and will have a light color shade. That’s because there wouldn’t be enough boiled linseed oil over the surface to protect the wood from moisture or other types of wood damage.
Boiled linseed oil has a thin flow because it is thinned with oil-based solvents, such as mineral spirits and turpentine. Since it is thin, the first coat automatically soaks in the wood when applied. So, you need a second coat to cover the surface and provide protection. This is why two coats are the minimum.
However, you can apply only 1 coat if you use raw linseed oil because it is thicker and offers more coverage.
When Do You Need Another Coat?
To know if you need another coat, touch the texture of the finish with your fingers after it has dried. If you can feel the wood grain with your finger, it means the wood oil was absorbed by the wood and didn’t cover the wood. So, you need another coat or two.
If you can’t feel the wood grain while touching the wood, it means the Linseed oil has formed a layer over the wood and will protect it. If this is the case, you don’t need an extra coating. However, you can apply one more coat to deepen the finish color.
You can also use the water test to know if you need another coat. Sprinkle water over the surface and wait a few minutes. If the wood absorbs the water, you need another coat. If the wood doesn’t absorb it, you don’t need another coat.
However, this test should be done after the wool oil has dried. When you have enough coats of Linseed oil, the finish will become water-resistant.
You can check the manufacturer’s instructions to know exactly how much of it you need. Manufacturers often recommend the number of needed for different types of materials and surfaces. So, check the bottle of the wood oil, or the manual (if it comes with one).
Dry Time Between Coats
It takes boiled Linseed oil 24 hours to dry between coats. However, its dry time depends on the porosity of the surface, the drying conditions, and the brand of the Linseed oil.
If you re-coat too soon, you will ruin the finish. That’s because the solvent of the wood oil will be trapped between both coats, meaning it won’t allow the existing or new coating to dry. This creates a sticky finish. To know for sure how long to wait between coats, check the manufacturer’s instructions.
Sanding Between Coats
You don’t have to sand between coats of boiled linseed oil. That’s because the coats stick to each other without sanding. Also, it doesn’t form a thick glossy finish that repels moisture, so the next coat sticks easier.
However, you can sand between coats to help the wood oil stick better and get a perfect finish. When you sand between coats, you improve the adhesion. Since the coats adhere better, the finish will be stronger and smoother.
Sanding helps to remove dust, debris, and grain that sits on the existing layer while drying. If you don’t remove the dirt, the finish will be riddled with bumps and might peel off.
To sand between coats of boiled linseed oil, you must use 400-grit sandpaper or 0000-grade steel wire. These two tools will polish and buff the finish but won’t remove it. You shouldn’t use coarse or medium-grit sandpaper as these grits are too harsh and might remove the wood oil.
You must apply 3-4 coats of boiled linseed oil on the hardwood. But, for softwood, you only need 2 coats.
Hardwood is more porous and accepts wood oil evenly. On the other hand, softwood doesn’t accept wood oil evenly, so you need a wood conditioner or a sanding sealer before applying it.
Cedar is a softwood so you need 2 coats of boiled linseed oil for a start. After applying them, check the wood surface to see if an extra coat is needed.
You must apply a coat of wood condition on cedar wood before applying boiled linseed oil. This helps the cedar wood absorb the wood oil evenly.
For worktops such as tabletops, workbenches, or countertops, you need 3 light coats of boiled linseed oil. However, you can apply 4 coats if the wood is very porous. Worktops experience a lot of usage, stain, and friction so they need more protection.
For outdoor furniture, you need 4 coats of boiled linseed oil. That’s because exterior furniture is exposed to dust, stains, moisture, and UV rays, so it needs more protection.
If you don’t use enough coats, the finish will get removed from the surface and expose the wood to the harsh exterior environment.
You should know that boiled linseed oil is recommended for interior applications and not for outdoor furniture. If you want to use boiled linseed oil on outdoor furniture, pick the brand that is designed for outdoor use.
The number of boiled linseed oil coats depends on the surface type and the brand type. However, the maximum number of coats you must apply is 4, while the minimum is 2 coats. 3 coats are the recommended amount.
Tony is a professional painter and an author of DIY Geeks. Tony has completed over 1,000 painting projects for his clients. It's safe to say he knows what he Is talking about,