Boiled Linseed Oil: For Wood and Metal

About Boiled Linseed Oil

Found in most woodworker’s workshops, as well as in trade shops up and down the UK, boiled linseed oil is a popular product at Rawlins Paints.

Also known as BLO (an acronym of Boiled Linseed Oil), this wood finish is an oil treatment primarily for interior use, which leaves a lovely and smooth finish on a wooden surface – almost with a wet look. Like the kiss of life, it can transform old, worn out and dried wood to better its former glory. Boiled Linseed Oil can be used on outdoor surfaces, but it lacks the resistance seen in modern products formulated for exterior work.

There are other wood finishes that treat surfaces in a different way, such as waxes, which ‘set’ the surface, sitting on it and buffing it to the desired finish. At Rawlins Paints we stock traditional wood oils (Danish, Teak, Linseed) and newer, advanced, next-generation wood products from Osmo that are much more user-friendly and combine the advantages of oils, waxes, and varnishes in one tin.

Boiled Linseed Oil – Its Many Uses

What is linseed oil used for?

Boiled Linseed Oil protects wooden surfaces with its deep penetration, soaking into the grain and bringing out added contrast and character. Rather than being a surface treatment, boiled linseed oil soaks deep into the wooden fibres, to the core of smaller depth pieces of wood, strengthening it throughout.

You may find it used on:

• Guitars – electric and acoustic, on the wooden body and neck
• Bannisters and Handrails
• Cabinets and Cupboards
• Rifles and Old Tool Handles
• Interior seating in Boats and Caravans
• Interior and Exterior Doors
• Speaker Cabinets
• Wooden Models and Crafts, such as cars and jewellery boxes
• Shelving and Mantelpieces
• Structural Beams

 

Fun Fact: Boiled linseed oil has not actually been boiled, but is chemically modified with metallic solvents for faster drying times. Standard or raw linseed oil can take weeks to dry, sometimes longer – making that the main difference between the two types of linseed oil.

Boiled linseed oil uses extends past wood protection, too – it also helps preserve metal, by protecting the surface from oxidation. Thin coatings work best, as thicker application coatings can take longer to dry and get, what is known in the trade, as ‘gummy’.

Generally, only applied to non-moving parts of workshop tools, such as chisels, block planes, screwdrivers or treasured (and no longer used) heirloom tools, it can also be used on cast iron surfaces of bigger tools – table and band saws for example.

How to Apply Boiled Linseed Oil

Boiled linseed oil is applied with a rag, or a similar buffering cloth. This is dipped into the linseed oil and rubbed into the wood – straight up and down the grain, or in slow buffering circles. Gloves should be worn at all times during the handling and application process of linseed oils.

You can also brush-apply boiled linseed oil onto bare wood. Using a minimum of 3 coats, the first two coats should be thinned 30% with white spirit. If used externally a wood preservative should be applied first.

Remember, as discussed earlier, to apply thin layers and not at any point by pouring the boiled linseed oil onto a surface.

Where possible, as with all paints and wood finishes sold at Rawlins Paints, it is best to test boiled linseed oil on a small area first, before applying full coverage.

Dry, bare wood is like a sponge and will soak up almost anything applied to its surface. Boiled linseed oil is one of many interior and exterior wood preparation products available, and acts as a good wood sealer to make surfaces much more water resistant.

Nearly all wooden surfaces will contract and expand through humidity and seasonal weather, which is where this type of linseed oil is great as it is flexible and will continue to protect the wood through these changes over time.

How Long Does Boiled Linseed Oil Take To Dry?

It may take between 24-72 hours for boiled linseed oil to fully cure, or dry out to the touch.

The Dried Out Finish

Similar to some other solvent based products, boiled linseed oil is cured by its interaction and chemical reaction with oxygen. When it dries, boiled linseed oil does create heat, in part of its chemical reaction with oxygen. Because of this there may be recommendations on a product for drying out (curing time) exposure to sunlight or other heat sources (ovens, radiators, naked flames), as well as for safe disposal of used cloths.

Chemistry states that lower usage of the product will create lower heat generating reactions, compared to larger application areas and density of the coating treatment creating potentially much bigger heat generation risk.

Removing Boiled Linseed Oil

The best technique to prepare a wooden surface for a treatment other than boiled linseed oil is to use sandpaper and a lot of elbow grease. As the oil soaks deep into the wood, you’ll be looking to prepare only the surface’s cured coating, removing as much of the linseed oil as possible.

Boiled Linseed Oil – Product Focus

Barrettine Boiled Linseed Oil is a traditional wood oil that works very well on most woods, with the exception of oak, and can be used inside and outside on soft and hard woods. Leaving an attractive warm mellow to an unpolished wood surface, it is water resistant and has a light satin finish. As well as sealing woods, it is also a traditional sealer for terracotta tiles. Every workshop should have a canister of Barrettine’s boiled linseed oil in a cupboard.

Why Can’t You Use Boiled Linseed Oil On Oak?

Oak contains a high level of natural water-soluble extractives and tannins, and some of these can react with the metal driers in Boiled Linseed Oil, turning black and discolouring the wood. These black spots can appear similar to mould spots.

Health and Safety

Boiled linseed oil does come with a strong warning that it is a very flammable material and incorrect storage can lead to spontaneous combustion. All product datasheets should indicate strict storage recommendations – including temperature, humidity, sunlight exposure, etc. for the storage area. If in doubt, please contact us prior to ‘forgetting’ about it and leaving it in an unsuitable environment.

One application method is to use a dry rag. After use, however, lay flat the rag on a non-flammable surface (concrete), away from potential heat/flame sources, until dry. Alternately, like the oil itself, the rag can be stored in a metal container. Never discard a used rag, as this can be a huge fire risk – the ‘screwed up’ and discarded rag can be a lot more heat reactive and combustible due to lack of air ventilation to cool the oil down. Used rags can be flash points, and at all times through the preparation, usage and cleaning-away process, all materials must be considered fire risks if inappropriately used and stored.