Raw Linseed Oil vs Boiled Linseed Oil

While linseed oil might be the base, there are a variety of different kinds of this type of oil. Two common types are raw linseed oils and boiled linseed oils, with stand oil being a noted variant.

I’ll tell you when to use each type of linseed oil, and what kinds of jobs they are best to be used. And, I’ll review the major differentiating factor between these three types of linseed oil. 

What is Linseed Oil? 

Linseed oil is an oil extracted from the seeds of the flax plant by pressing the seeds or soaking them in a solvent. It is clear or has a slight yellow tinge. 

Edible versions of linseed oil are known as flax oil or flaxseed oil. It can be used to add flavor to bland, acid-set cheeses like quark or formulated into capsules and sold as a dietary supplement. Linseed oil contains ALA, a fatty omega-3 acid. 

Linseed oil belongs to a category of substances called ‘drying oils’, which harden via polymerization. When not modified, it is known as raw linseed oil, and can take months to fully dry. 

What Is Raw Linseed Oil?

Raw linseed oil refers to 100% linseed oil that has not been processed and does not contain driers or thinners. When modified, raw linseed oil can be turned into stand oil or boiled linseed oil. 

On its own, raw linseed oil can take more than two months to dry, making it unappealing for use as a wood finish for household items, decking, furniture, or wooden flooring. 

However, this prolonged wetness makes raw linseed oil ideal for treating the willow bats used in cricket. Raw linseed oil is purported to lock in moisture and hold the wood fibers together, while providing a springy surface and increased surface friction for better ball control. 

This increased surface friction also makes raw linseed oil an effective treatment to prevent slippage on automotive machines that use rubber belts. 

Raw linseed oil can be modified to create two subtypes of linseed oil. One such modification is achieved by trapping linseed oil in an oxygen-free environment and heating it to temperatures above 300 degrees, then holding it there for a period of several days. This process converts linseed oil into a new substance known as stand oil. 

What Is Stand Oil? 

Stand oil is modified linseed oil mostly used in fine art. High heat and no oxygen force the molecular conversion of raw linseed oil into a highly viscous substance with a honey-like consistency. When it dries, stand oil is much more elastic than raw linseed oil would be. 

Stand oil is known in the fine art world as an oil painting medium. It is brushed onto the workpiece, and then oil paints are applied on top. 

Stand oil allows color to flow after application, minimizing brush strokes. When solvents are added to paint, they speed the dry time. Using stand oil as a painting medium can help combat this, giving the artist a longer period of time to work.  

In ‘fat over lean’ painting, the ratio of color to painting medium increases with each layer of paint. It is thought that this will help the color to stay flexible and reduce cracking over time. In this method, stand oil is used as a medium in the top most, oil-heavy layers. 

Stand oil can also be used for another fine art technique known as glazing. Glaze is a protective clear coat added to finished oil paintings. Stand oil is clear, and will not yellow over time, making it perfect for this use. Stand oil is lightly brushed over the entire painting and allowed to dry. 

Stand oil is also used to create boiled linseed oil. 

What Is Boiled Linseed Oil?

Boiled linseed oil is a mixture of stand oil, raw linseed oil, and oil drying agents. These agents, called catalysts, significantly accelerate the dry time of boiled linseed oil over raw linseed oil or stand oil alone. 

Decreased dry time makes boiled linseed oil suitable for use as a wood finish. It is known as a penetrating or impregnating finish, because the oil seeps into the pores in the wood. Boiled linseed oil, or BLO, cures to a hard barrier through a process of polymerization called crosslinking. 

Boiled linseed oil is generally applied to clean, sanded wood, using a lint-free cloth or rag. It is allowed to soak into the wood for a short period of time, usually less than 30 minutes. Any excess oil must be soaked up with rags until the surface of the wood feels dry. The curing process happens over the next 30 days or so. 

Once cured, wood treated with boiled linseed oil will appear richer in color and less dry. It will also repel water. When UV-absorbing materials are added to boiled linseed oil, it can provide protection from fading and weathering. 

Boiled linseed oil is often used to protect outdoor furniture and exterior trim.

Boiled linseed oil can also be applied to metal to discourage oxidation. Multiple thin applications with adequate dry time in between achieve a shiny, clean surface that will not rust. 

Raw Linseed Oil vs Boiled Linseed Oil vs Stand Oil

Now that you know the basics about these three related substances, it’s time to explore their similarities and differences. 

Similarities

Raw linseed oil, boiled linseed oil, and stand oil come from the same source, are all drying oils, and carry a risk of spontaneous combustion. 

Origin

All three oils originate from the seeds of the flax plant. 

Drying Oils

These three substances are all drying oils, which means they harden through polymerization during the cure phase of application. 

Fire Risk

All linseed oils generate heat as they dry. Where the oil has been applied to a surface in thin layers, the heat easily dissipates before reaching the flash point temperature where spontaneous combustion can occur. 

However, the rags used to apply linseed oils tend to get wadded up and thrown in the trash. With no way for the heat to escape, the much lower flash point of fabric can easily be reached, starting a fire in your workspace. This is often referred to as spontaneous combustion.

This risk is easily preventable. Simply lay soaked rags out to dry until they are crusty and no longer wet. They can then be safely disposed of in a landfill. 

Differences

Despite originating from the same seed, these three oils are different thicknesses and are used in different ways. 

Viscosity

Raw linseed oil is thinner than either stand oil or boiled linseed oil. Stand oil is the thickest substance of the three; the viscosity can be compared to honey. Boiled linseed oil contains both products, and sits somewhere in the middle in terms of thickness. 

Use

Stand oil is only used in the creation of fine oil paintings. Raw linseed oil is primarily used to create boiled linseed oil, although some cricketers still use it to oil their bats. Boiled linseed oil is the only one of the three products with a fast enough drying time to be used as a wood or metal finish. 

Major Differentiating Factor

Boiled linseed oil is the only one of the three suitable for use as a wood or metal finish. 

Raw linseed oil and stand oil have very limited applications. Each can only be used in one specific way. Boiled linseed oil is much more versatile. It contains both stand oil and raw linseed oil, but metallic salts have been added to speed the drying process.

When to Use Raw Linseed Oil

Use raw linseed oil to condition willow cricket bats. 

When to Use Stand Oil

Use stand oil as an oil painting medium, especially when using the ‘fat over lean’ technique of building layers of paint. Stand oil can also be used as a finishing glaze over completed oil paintings. 

When to Use Boiled Linseed Oil

Use boiled linseed oil to protect wood from moisture, fading, and weathering. Maintain your garden tools or metal edges and protect them from oxidation with thin coats of boiled linseed oil. 

Which Is Better, Raw Linseed Oil, Stand Oil, or Boiled Linseed Oil?

Boiled linseed oil is the most useful and versatile of the three oils mentioned here. It contains both raw linseed oil and stand oil. It is best for finishing exterior furniture and preventing rust on metal. 

Stand oil is best for fine art. Raw linseed oil is best for oiling the wooden bats used to play cricket.