The quality of the wood finish is what separates average wood products from superior pieces of art. The proper finish applied with skill gives the wood surface a lustrous, rich look and improves the overall appearance many times. You can transform old and dilapidated pieces into looking as fresh as the day they were oiled and keep newly finished pieces looking great. But with a lot of misinformation on proper oil finishing techniques, applying an oil finish may not be as straightforward as it seems. One of the more controversial questions is how many coats of boiled linseed oil?
When applying boiled linseed oil, most experts recommend three coats. After you apply the first coat and letting it dry thoroughly, you can then lightly sand the surface and apply the second coat. You then follow a similar process before applying the third and final coat. Three coats will ensure that the boiled linseed oil has fully saturated the wood fibers.
Linseed oil is obtained from pressing the seeds of the flax plant and is also known as flaxseed oil. There is evidence of its use from ancient times, and it is still relevant today. A variant of linseed oil, boiled linseed oil, is prized in wood, finishing its properties such as ease of use, quick drying time, and aesthetics.
Why Should You Use Boiled Linseed Oil?
The popularity of boiled linseed oil as a wood finish is well-deserved. Some of the main benefits of using it include:
- Boiled linseed oil brings out and showcases the texture and the color depth of the wood grain.
- You can use it with other wood finishes, such as wax, to offer additional wood protection.
- Boiled linseed finishes are easy to repair. You can easily sand out any dents or scratches, and a new oil coat applied.
- The oil also deeply penetrates the wood grain.
Do You Sand Between Coats of Boiled Linseed Oil?
Yes, you do. The smooth oil finishes are typically created by sanding between the applied coats using fine-grit sandpaper such as the #320 grit or an even finer one. For the best results, you should make sure that you allow each applied coat to cure fully. Leave the wood in a warm room to dry overnight. Most oil finishes that you purchase will come with instructions regarding the amount of time needed to cure them entirely.
To get the smoothest finish possible, you can sand each coat while it is still very wet on the surface. Stearated or dry-lubricated sandpapers work best for this as they have some of the same soap-like ingredients as sanding sealers, and they clog up less.
How Should You Apply Boiled Linseed Oil?
Woodworkers mainly use boiled linseed oil to finish wood that will often or permanently remain indoors. This use includes indoor furniture, paneling, beams, floors, and indoor furniture. Since boiled linseed oil is a penetrating finish, i.e., it does not harden, and after each coat, you must wipe off the excess. You can only apply it to wood that you have previously oiled. Wood that had previously been varnished; painted r waxed would prevent the penetration of the oil. If the wood already had either one of these finishes, you should, therefore, clean and strip the bare wood before applying linseed oil.
Step 1: Gather the needed tools and materials.
Ensuring you have all the tools you need before getting started will ensure that you work faster and more conveniently. The tools and material you will need include.
You will need sandpaper of different grits depending on the type of wood and when you want to do the sanding. If you are working with previously used or damages wood, you will need sandpaper with grit ranging from 80 to 180 for old wood and upt0 around 320 for damaged surfaces, as well as a mechanical sander.
For new wood, you can use 120 – 180 grit sandpaper and work your way up if you need more grit.
A 320 to 400 grit paper will work well to sand the wood between coats of finish.
- An applicator
The applicator is the material that you will use to apply the boiled linseed oil onto the wood. You can use either a stiff bristle brush or a cotton rag.
- A clean rag to use to wipe off the excess oil after application.
- A mixing container with an airtight lid to use for storing the oil between applications.
- The boiled linseed oil.
Step 2: Prepare the surface.
You will need to sand and dust the wood surface to ensure better linseed oil penetration. Sand the wood surface with sandpaper of grit between 320 to 400. While other surface coatings may hide coarser or medium scratch marks on the wood, the oil will only accentuate them as an oil finish does not have any measurable build. If you want to get an even more refined finish, you can intentionally raise the wood grains and then sand again to knock off the raised fibers. The grains can be raised by wetting the wood surface and then letting it dry.
Before advancing to finer grit sandpaper, you will also need to remove the dust build-up. A vacuum is the best tool you can use as it gets rid of the dust once and for all. You can also use a brush, but dust brushed away to the floor can eventually stir up again and end up on the wood. If you do not have a vacuum, you can use a wet rag to wipe away the wood’s surface. Tacky rags get loaded full of dust too quickly and would work best for minor characters or when you are sanding between coats of finish. If your workshop has a sound exhaust system, compressed air is another great way to eliminate dust.
One of the biggest challenges for novice woodworkers is knowing when to stop sanding. This knowledge will come with experience, but there are some ways you can also use it to know when to stop. After dusting off the wood, look at it in a low angle reflected light or wet the wood, then observe it at different angles in reflected light.
Step 3: Application
There are two basic ways you can apply boiled linseed oil to the wood surface. First, you can pour it directly from the can onto the wood and then use your rag to apply. We do not recommend this method as you will have little to no control over the application process and a greater chance of waste by pouring more than you need. Second, you can stream the boiled linseed oil into a bowl, then dip a rag and use it to apply.
When applying the oil, start with the wood’s hard-to-reach parts such as corners to avoid contact later in the application. Rub the cloth along the wood grain or use slow, buffering circles across the wood grain. The purpose of the first coat of linseed oil will be to saturate the wood as deeply as possible. Reclaimed and dry wood will suck in the oil like a sponge. If your wood sucks in the oil, repeatedly reapply until the surface is wet for the next few minutes until you are sure the wood is saturated.
Apply the BLO generously but in controlled amounts. The wood surface should appear very wet, but there should be no puddles on the surface. If puddles do form, wipe the excess away with a piece of cloth. Keep an eye on the wood for the next few hours and wipe away any oil that bubbles to the surface.
Step 4: Application of subsequent coats.
Application of the next coat will depend on the drying time for the first coat. Factors such as the room temperature, humidity, and the thickness of the layer will influence how quickly it dries. For faster drying time, store the wood in a warm room overnight. Leaving it to dry overnight should be sufficient in most cases. Pass your hand over the wood surface and give it more time if it feels tacky. If the surface is somewhat slippery and dry to the touch, it is dried sufficiently.
After ascertaining that the surface is dry, you can then proceed to do a very light sanding on the first coat of linseed oil. After sanding, you can then apply the next oil coat. Typically, you will need to use around three coats of BLO for the best results. After applying the final coat, you will not need to sand the wood surface; only fully cure it.
How Long Does It Take for Boiled Linseed Oil to Dry?
It takes between 24 and 36 hours for a single coat of boiled linseed oil to get completely dry to the touch. Since linseed oil is a drying oil, it polymerizes into a solid form. Woodworkers have exploited the drying properties of oil for most of its applications. In stark contrast to raw linseed oil that takes several days to sometimes a week or more to dry, boiled linseed oil has a drastically shorter drying time.
Several other factors affect the drying time of boiled linseed oil, such as the room humidity and temperature and the amount of BLO you have applied. The more oil you apply, the more time it takes to dry. Therefore, after applying BLO to the wood, use a rag to wipe away any excess oil. The surface should look wet, but no puddles should form. Also, store the wood product overnight in a warm room for faster drying. The room should also be well-ventilated and have low humidity to facilitate speedier evaporation. When using raw oil, you can thin it out with a drying agent to reduce the drying time.
You will know if your coat of boiled linseed oil is dry if, after passing a dry cloth on the surface, the fabric remains dry and if the surface does not feel sticky to the touch.
How Long Does Linseed Oil Last on Wood?
After applying the boiled linseed oil, you can use them for half a year to a year before you need to do maintenance, depending on the amount of use that the product sees. You will know you need to reapply another BLO coat is when the wood starts appearing dry or discolored. Wood pieces on frequently used areas such as floors and furniture will need maintenance more often than areas such as beams.
To reapply another boiled linseed oil coat, first wipe down the wooden piece using a soft, clean, lint-free cotton cloth. Then apply a light coat of the boiled linseed oil, wipe away the excess BLO and allow the oil to dry.
Routine cleaning of your wood pieces will also help them keep looking good for a long time to come. It would help if you cleaned any liquid spills as quickly as possible before it penetrates the wood fibers. Other factors such as the environmental conditions will affect the life of your finish. Wood is quite sensitive to changes in relative humidity, which affects the wood’s moisture content.
Experts recommend conditions of up to 72 degrees Fahrenheit and relative humidity of around 50 to 55%. Most woods are also sensitive to light intensity for long periods, so you should be careful to match the type of wood you use with the conditions of use. Wood pieces that are mainly outdoors will require maintenance more often as they are more exposed to harsh conditions.
What is the Difference Between Linseed Oil and Boiled Linseed Oil?
The main difference between linseed oil and boiled linseed oil is the drying time, with boiled linseed oil used when faster drying is required. Below is an analysis of the fundamental differences between these two variants of the same oil.
Raw linseed oil is linseed oil that is 100% pure. You can obtain it from the pressing of flax seeds without any further processing or addition of thinners and driers. Raw linseed oil takes several days to fully dry and does not cure well enough to be classified as a drying oil. This long drying time makes it suitable for wood objects where the drying time is not a significant consideration.
Boiled linseed oil, unlike the name suggests, is not boiled. Manufacturers treat it with metallic or petroleum-based oil drying agents that make it dry faster. It gets its name from when people boiled linseed oil in the medieval era with lead oxide. Some of the petroleum-based products added include naphtha, di-propylene glycol monomethyl, and mineral spirits, while some of the metal additives include cobalt and manganese.
Due to all the additives, boiled linseed oil may not be the best choice for you looking for a natural product. It is also not recommended to use BLO on products that can contact food, such as cutting boards. You can, however, use it in almost all other wood items. The drying time for boiled linseed oil is also around 24 hours, making it more convenient to use.
Apart from raw and boiled linseed oil, another variant of linseed oil is stand oil. This variant is linseed oil heated to about 300 degrees Celsius in an environment completely devoid of air. This heating product is a highly viscous substance and gives uniform coatings that, when dry, are more elastic than linseed oil. Layers from stand oil are also less prone to yellowing. Stand oil, like raw linseed oil, has zero volatile organic compounds.
The main differences between boiled and raw linseed oil include:
- The drying time – as mentioned above, natural linseed oil takes several days and sometimes up to a week to dry, while boiled linseed oil takes about 24 hours.
- Appearance- Boiled linseed oil will give a slightly glossy look and has a uniform finish. On the other hand, Raw linseed oil is not polished but has a shiny appearance and accentuates the wood grain.
- Toxicity- Raw linseed oil is an entirely natural product that is usually not toxic (you will need to check the can instructions to see if there are any additives). The finish it gives is not water-resistant and is easily scratchable. Boiled linseed oil has additives that can be toxic, and it provides a hard-wearing finish.
- Use- Raw linseed oil is typically used to oil cricket bats to give better ball control and increase surface friction, combined with paints and stains, and used in treating leather flat belt drives to prevent and reduce slipping. You can finish interior wood with BLO, but you cannot use it with exterior oak.
How long Does Boiled Linseed Oil Take to Cure?
Though it has a short drying time, boiled linseed oil only fully cures after 30 to 45 days. Although people sometimes use the terms interchangeably, they are two distinct processes with significant differences. After applying linseed oil, after the surface dries, this does not fully cure it. Drying occurs when the solvent has evaporated from the coating. As mentioned above, it takes around 24 hours in boiled linseed oil. On the other hand, curing is the chemical process through which the coating fully toughens and hardens. Linseed oil cures through oxidation to create a hard film.
The entire curing process takes around 30 to 45 days. While you can use your wood product after the finish is dry, you should refrain from subjecting it to hard use.
Safety Tips When Using Boiled Linseed Oil
One of the most high-profile cases that shows the potential hazard of boiled linseed oil is the 1991 fire of the One Meridian Plaza in Philadelphia. The building was damaged quite severely, and three firefighters died in a fire whose cause is believed to be from rags that someone had soaked with linseed oil. Another famous example of linseed oil’s destructive capability is the spontaneous combustion of the mummy of Tutankhamun after being embalmed with linseed oil and not give enough curing time.
But what property of linseed oil makes this wood finishing product a fire hazard? The oxidation process of linseed oil is exothermic, a feature that may lead to spontaneous combustion. When you soak a rag with linseed oil, it provides a larger surface area for rapid oxidation. This property is why you should store linseed oil and the based products in airtight containers.
The expert tips below will help you stay safe as you use boiled linseed oil.
- For long-term storage of boiled linseed oil, use metal containers. You can use a plastic bowl or container for short-term storage but transfer it into a metal container for the long term.
- Store boiled linseed oil in a container that has an airtight seal.
- Keep the container with the boiled linseed oil in a cool location away from foods and beverages and compatible materials.
- You should not ball up used rags. When you wad up a rag, there is no air to pass over its surface and cool it. Therefore, lay the cloth on a flat surface and away from any flammable substances until it fully dries or hung the rag to air dry. You can also store the rags in a water-filled metal container.
- Keep an emergency eyewash near your workstation to use the oil that gets into your eyes.
- Get respiratory protection to protect you from dust particles after sanding down the wood.
- Invest in gloves that are impervious to boiled linseed oil and dispose of the gloves accordingly.
- Strictly follow the safety recommendations indicated on the container by the manufacturer.
Applying boiled linseed oil to your wood pieces is an excellent way of restoring old projects and keep new ones looking good. It is important to note, though, that you cannot substitute linseed oil with wood preservatives. If you plan to use the wood outdoors, be sure to treat it first to make it weather and insect-proof. For the woodworker who is interested in finishing their project with boiled linseed oil, the vital question is,
How many coats of boiled linseed oil?
Three coats of linseed oil will be more than sufficient to give your wood project a rich finish that will last for months before needing repair and maintenance.
Thank you for reading this article, especially if you made it to the end. We hope that it has been informative on the subject matter and answered thoroughly any questions you may have had. The comment section below is free for any comments, suggestions, or queries.