What Is Linseed Oil? Key Concepts and Applications
What is Linseed Oil for?
Linseed oil is derived from the flax seeds. The sources of both the flaxseed oil and the linseed oil are the same, however, their processing is different. Linseed oil is used in industrial purposes whereas flaxseed oil is used for consumption since it is proven to be healthy. Flax is amongst the most commercially important and the oldest crops that are grown in the colder climates. Flax seeds are consumed as a healthy diet since they are rich in dietary fibre and omega 3 fatty acids. The linseed oil is derived from both the different types of flax seeds and they have a yellow colour.
Properties of Linseed Oil
The properties of the linseed oil that make them suitable to be used in the industrial purposes are given below.
Drying Properties:
The linseed oil tends to dry uniformly, however, at a slower rate. Because of this characteristic, it is used in the form of a drying agent in the paint formula, wood finish products, etc.
Imparts Glow:
The linseed oil makes the wooden surface glow.
Water Resistance:
It tends to keep the surfaces safe from the water and hence, prevents the materials and metal products from undergoing corrosion, and the furniture from the damages by water.
Building Properties:
The linseed oil helps to bind the ingredients in several products. It helps in creating a rich and smooth emulsion when all the ingredients get mixed with one another.
Linseed Oil Structure
The linseed oil structure is given below.
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What is Linseed Oil Used for?
Talking about what is linseed used for, here are some of its uses given below.
Linseed oil has its use in the paints for making them more glossy, transparent and fluid.
It is also used in the form of a sealant for the glass windows that tends to harden in a few weeks after the application is done and can then be painted.
The linseed oil is also used by the billiards and the pool cue makers to make cue shafts.
It is used to manufacture linoleum which covers the floors.
It has its use by the luthier for reconditioning the fretboards of the string instruments like mandolin, guitar, violin, etc.
It is also used in the method of traditional oil gilding for sticking the gold leaf sheets to the sub.
What is Boiled Linseed Oil?
The boiled linseed oil consists of a combination of the raw linseed oil, metallic oil drying agents and the stand oil. During the medieval era, the linseed oil was allowed to boil along with lead oxide for giving the boiled linseed oil. The lead oxide used forms lead soaps since it is alkaline in nature, and it promotes polymerisation or hardening of the linseed oil when it reacts with the atmospheric oxygen. The heating process tends to shorten the drying time.
What is Boiled Linseed Oil Used for?
The boiled linseed oil is used for giving a mellow and patented finish to the stripped or newer bare interior wood. This oil is a high and superior quality oil, which is much similar to the raw linseed oil. However, it contains hot air which has been passed through it for improving the drying times. The boiled linseed oil can be used on all different kinds of woods except for the exterior oak. It is also used in the form of a traditional sealer in the stone floors, terracotta tiles, and many other porous surfaces before they undergo waxing.
FAQs on Linseed Oil: Chemistry, Properties & Uses
1. What is linseed oil chemically composed of?
Linseed oil is a type of triglyceride, similar to other fats and oils. Its unique properties come from its high concentration of α-linolenic acid, a polyunsaturated fatty acid. The typical composition includes:
- Triply unsaturated α-linolenic acid (about 52-55%)
- Doubly unsaturated linoleic acid (about 14-17%)
- Monounsaturated oleic acid (about 18-23%)
- Saturated acids like palmitic and stearic acid (about 10%)
2. What are the most common uses for linseed oil?
Linseed oil is primarily used as a drying oil. This means it can harden into a solid film. Its main applications include:
- Wood Finishing: To protect and beautify wood furniture and floors.
- Paints and Varnishes: It acts as a binder, holding the pigment and forming a durable coating.
- Putty: It's a key ingredient in traditional window glazing putty.
- Sports Equipment: Used to condition and protect wooden items like cricket bats.
- Linoleum: It is a primary component in manufacturing linoleum flooring.
3. Why does linseed oil harden when exposed to air?
Linseed oil hardens through a chemical process called oxidative polymerization, not by evaporation. Its high content of polyunsaturated fatty acids reacts with oxygen from the air. This reaction causes the oil molecules to link together (polymerize), forming a solid, dry, and durable film. This is why it's valued as a 'drying oil' in paints and finishes.
4. What is the difference between raw and boiled linseed oil?
The main difference is the drying time and purity. Raw linseed oil is the pure, unadulterated oil extracted from flax seeds; it is very slow to dry, often taking weeks. Boiled linseed oil isn't actually boiled. It's treated with chemical additives (metallic drying agents) that significantly speed up the polymerization process, allowing it to dry in a day or two.
5. Is it safe for humans to eat linseed oil?
It depends on the type. The oil sold for human consumption is called flaxseed oil and is processed for purity. The industrial product sold as linseed oil, especially 'boiled linseed oil', often contains toxic solvents and drying agents and is not safe to eat. You should only consume oil specifically labelled as food-grade flaxseed oil.
6. How is linseed oil different from common cooking oils like sunflower or olive oil?
The key chemical difference is the degree of unsaturation. Linseed oil is extremely rich in polyunsaturated fats (especially omega-3 alpha-linolenic acid), which are highly reactive with oxygen and allow it to polymerize or 'dry'. Common cooking oils, like olive oil, are high in monounsaturated fats, which are much more stable and do not harden in the same way, making them suitable for cooking but not for creating protective coatings.
7. Which plant does linseed oil come from?
Linseed oil is extracted from the dried, ripe seeds of the flax plant, whose scientific name is Linum usitatissimum. This is the very same plant that is cultivated to produce linen fibre for clothing and textiles. In India, the seeds are commonly known as 'Alsi'.
