Boiled or Raw Linseed Oil, Which to Use and Why

Choosing between Raw Linseed Oil (RLO) and Boiled Linseed Oil (BLO) is a classic woodworking debate. While they both originate from the same tiny flax seed, the manufacturing processes turn them into two very different animals in terms of performance and application.

Here is a deep dive into the science, the "why," and the practical applications.

The Manufacturing Process: Science in a Tin

The fundamental difference lies in how the oil is treated to change its polymerisation (drying) speed. Linseed oil does not "dry" through evaporation like water; it hardens through a chemical reaction with oxygen.

Raw Linseed Oil (RLO)

RLO is as pure as it gets. It is simply pressed from flax seeds and bottled.

• The Process: Cold-pressing or solvent extraction. There is no heat treatment and no chemical additives.
  The Result: A thin, highly penetrating oil with a very simple molecular structure. Because it hasn't been "pre-started," the oxidation process is incredibly slow.
  

Boiled Linseed Oil (BLO)

The name is a bit of a historical misnomer. Modern BLO isn't actually "boiled" in an open pot any more.

• The Process: It is heated in a vacuum to increase its viscosity and start the polymerisation process. Crucially, metallic driers (such as manganese, cobalt, or zirconium) are added.
  The "Why": These metals act as catalysts. They grab oxygen molecules from the air and force them into the oil's molecular chain, making it harden in hours rather than weeks.
  

Comparison at a Glance

Feature	Raw Linseed OIl	Boiled Linseed Oil
Drying Time	2-4 weeks per coat	12-24 hours per coat
Additives	None (100% Pure)	Metallic chemical driers
Finish	Very matte, deep soak	Satin sheen, builds a 'film'
Food Safety	Usually food-safe	Not food-safe (toxic driers)
Water resistance	Low (remains flexible)	Moderate (harder surface)

When to Use Raw Linseed Oil

Raw oil is for the patient craftsman or for specific functional requirements where purity is king.

• Cricket Bats: This is the gold standard for cricket bats. It keeps the willow fibres supple and prevents the wood from becoming brittle under the impact of a ball.
• Food-Contact Surfaces: Because it contains no toxic driers, it is often used for chopping boards, salad bowls, and wooden spoons (though it does take ages to dry).
• External Oak Beams: In heritage restoration, RLO is used because it penetrates deeper into dense hardwoods than BLO, providing "internal" protection that moves with the wood.

The Downside: If you apply RLO to a piece of furniture indoors, it will remain tacky for weeks, attracting dust and pet hair. It is also prone to mildew in very damp environments.

When to Use Boiled Linseed Oil

BLO is the industrial workhorse. It is what most people actually need when they ask for "linseed oil."

• Furniture & Cabinetry: It brings out the "chatoyance" (depth) of the grain beautifully and dries fast enough to apply multiple coats in a few days.
• Tool Handles: It is the classic choice for hammers, axes, and chisels. It provides a "grippy" finish that doesn't blister the hands like varnish might.
• Sealing Terracotta: It is excellent for porous floor tiles, providing a hard-wearing, water resistant seal.
  

The Downside: The metallic driers make it unsuitable for anything that touches food. It also generates heat as it dries, improperly stored rags soaked in BLO can spontaneously combust.

The Verdict: Which one should you choose?

Choose Boiled Linseed Oil for 90% of general projects. It is faster, harder-wearing, and provides a more professional looking finish. It’s the "practical" choice for modern life.

Choose Raw Linseed Oil only when you need the finish to be 100% non-toxic, or if you are treating a specific item (like a cricket bat or heritage timber) that requires the wood to remain exceptionally flexible over a long period.

Important Note: Always remember to lay the oil-soaked rags flat outside to dry before disposing of them. The oxidation process in BLO creates heat, and a crumpled rag in a bin is a genuine fire hazard!

How to Apply Boiled Linseed Oil (BLO)

The "Fast & Hard" Method

BLO is designed to build a protective film. The secret is applying thin layers and never letting the oil "puddle."

1. Preparation: Sand the wood to at least 180 or 240 grit. Remove every trace of dust with a tack cloth or a damp rag, then let it dry completely.
2. The First Coat: Apply the oil liberally using a lint-free cloth or a natural bristle brush. You want the wood to look "wet."
3. The 15-Minute Rule: Allow the oil to penetrate in to the wood for 15 minutes. If the wood "drinks" the oil and looks dry in spots, add a little more.
4. The Great Wipe-Off: This is the most important step. Take a clean, dry rag and wipe off every bit of excess oil until the surface feels dull and almost dry. If you leave it "wet," it will turn into a sticky, gummy layer that is a nightmare to remove.
5. Curing: Leave it to dry for 24 hours in a well-ventilated, warm room.
6. Repeat: Lightly "de-nib" the surface with very fine steel wool or 400-grit sandpaper, wipe away the dust, and repeat for 2–3 more coats.

How to Apply Raw Linseed Oil (RLO)

The "Deep & Patient" Method

Because RLO is 100% pure and slow curing, the process is about deep saturation over time.

1. Preparation: As with BLO, ensure the wood is clean, sanded, and bone dry.
2. Thinning (Optional but Recommended): Because RLO is quite thick, many craftsmen mix the first coat 50/50 with pure turpentine or white spirit. This helps the oil "dive" deeper into the wood grain.
3. Application: Rub the oil into the grain using a cloth. You can be quite vigorous here, the friction helps the oil penetrate.
4. The Waiting Game: Let it sit for 30–60 minutes. Unlike BLO, you don't need to panic about it drying too quickly, as it stays liquid for a long time.
5. Wipe Down: Wipe off the excess thoroughly. The surface should have a matte glow but no standing liquid.
6. The Long Cure: You must wait at least 3 to 7 days before applying the next coat. If you apply a second coat while the first is still liquid inside the wood, it may never fully harden.
7. Maintenance: RLO is often a "lifetime" finish. For items like cricket bats or heavy oak beams, one or two coats a year will keep the timber supple and healthy.

To view our Raw or Boiled Linseed Oil, click the link below:

Raw Linseed Oil

Boiled Linseed Oil