Linseed oil is a mixture of fatty acids, proteins, waxes and antioxidants. Of these, only the unsaturated fatty acids have the properties necessary for linseed oil paints and impregnation oils. All other components of the linseed oil impair the end result.
Unsaturated fatty acids oxidize with the oxygen in the air, forming molecular chains. These form an elastic polymer called linoxyn. It is water-repellent and resists fats, petroleum products, salts and household acids, e.g. lemon, wine and vinegar. No living organism can digest linoxyn, so it is indefinitely durable. We remove the other constituents of linseed oil by refining, and recover the unsaturated fatty acids. We boil them in different ways to produce various oil products with optimal viscosity and curing time for the intended use, i.e., impregnation of wood, polishing of wood, rustproofing and protection of porous stone.
Linseed oil was refined in a comparable way to make the best linseed oil paints and linseed oils until the mid-20th century. The process was very time consuming, and it fell into oblivion after the synthetic paints had made their breakthrough.
The chemistry of drying oils
Linseed oil contains two drying fatty acids: linoleic acid, the molecules of which contain two double bonds between oxygen atoms, and linolenic acid, which contains three. These can create molecular chains of practically unlimited length, polymerize, by oxidation.
An oxygen atom in e.g. the air creates a bridge between two fatty acid molecules by bonding to one of the bonds of a double bond between oxygen atoms in each molecule. Thereby the fatty acid molecules are united into a bigger molecule. Since the linoleic acid can bond to two other fatty acid molecules and the linolenic acid can bond to three, the polymerization can continue until giant molecules have formed. The end result is an elastic polymer called linoxyn.
Linseed oil also contains oleic acid, the molecules of which contain one double bond between oxygen atoms. It can form only one oxygen bond with another fatty acid molecule, and therefore can become part of giant molecules of linoleic and linolenic acid, but cannot form giant molecules on its own.
All other components of linseed oil impair the drying, colour fastness, durability and mould resistance in oils and paints.
Components detrimental to linseed oil paints as well as to impregnation- and polishing oils
The tendency of linoleic and linolenic acids to polymerize with oxygen constitutes a threat to the germinability of the seed. Therefore, antioxidants, primarily tocopherol (i.e., vitamin E), are formed in the seed.
Unless the antioxidants are removed, the linseed oil paint takes a week or longer to dry, often incompletely. This problem can be addressed by adding a siccative, usually cobalt zirconium carboxylate. This makes the paint skin, i.e., not dry all the way through but only on the surface. To counteract skinning, 2-butanone oxime is often added.
The success with these chemical additives varies. The presence of antioxidants is the reason why linseed oil paint work manuals usually state that one should paint very thin coats; that one should not paint in sunlight, and only during the warm season, and that linseed oil paint dries much slower than alkyd paint (read more on alkyds below).
Selder & Company has solved this problem by removing the antioxidants.
Linseed oil contains beta-carotene, an antioxidant that turns yellow over time. This permanent yellowing should not be confused with the photochromicity of linseed oil, i.e., it yellows in darkness and whitens in a few hours when exposed to light.
Selder & Company has solved this problem by removing the beta-carotene.
Saturated fatty acids
Linseed oil contains two saturated fatty acids, stearic and palmitic acid. These do not dry, as they do not contain double bonds between oxygen atoms. Instead, they go rancid, react with water and nourish microorganisms. Therefore, manufacturers of linseed oil paints often add a fungicide.
Furthermore, stearic and palmitic acid decompose rather rapidly, which causes binder to disappear, leaving pigment specks bare and causing the paint to become chalky. Linseed oil paint work manuals often state that the paint has to be freshened up every few years. When oil, varnish or paint containing these fatty acids are exposed to moisture, white spots of oil/water emulsion, which can be wiped off with a finger or a cloth, appear on the surface.
Selder & Company has solved this problem by removing these fatty acids.
Waxes on the seed coat turn into a sticky gel with water. This enables linseed to stick to passing animals and spread with them. When oils, varnishes or paints that contain such waxes are exposed to moisture, white spots of gel, which can be wiped off with a finger or a cloth, appear on the surface.
Selder & Company has solved this problem by removing the waxes.
Proteins provide excellent nourishment for all living organisms and decompose easily. This is the most important ingredient in the biological decomposition of linseed oil.
Selder & Company has solved this problem by removing the proteins.
Alkyd oil paints are made with polyester, a plastic
Wikipedia: An alkyd is a polyester modified by the addition of fatty acids and other components. They are derived from polyols and a dicarboxylic acid or carboxylic acid anhydride. (…) The inclusion of the fatty acid confers a tendency to form flexible coating. Alkyds are used in paints (…). They are the dominant resin or 'binder' in most commercial 'oil-based' coatings…”
Quote from The Swedish National Heritage Board, Materials guide on alkyds (our translation): "Flax, soybean and pine oil are the most common starting products, but fish oil, Chinese wood oil, safflower oil, as well as non-drying oils such as coconut and castor oil and synthetic fatty acids are also used."
Quote from The Swedish National Heritage Board, Materials guide (our translation): “During some time, alkyd oil paints were used for restorations as a substitute for linseed oil paint. But although the drying times were shorter and they had better impact resistance [NOTE: compared to linseed oil paints made from UNREFINED linseed oil - i.e., this does NOT apply to Selder's linseed oil paints!], the alkyd paints had difficulty meeting the requirements regarding adequate penetration, elasticity and an authentic appearance during aging and degradation.”
Selder & Company's linseed oil paints are true oil paints.
By applying modern process engineering to the old art of refining linseed oil, we produce clean unsaturated oils. Pumps, containers, pipes and process vessels are as far as possible made from stainless and/or acid-proof steel. This enables us to maintain the high production hygiene necessary to make products of a high and consistent quality. The raw materials are fed to the process via PLC-controlled scales and automated valves, thereby ensuring that the exact amounts are added at exactly the right times and that the end products always have the correct properties.
The refined linseed oil is used as binder in Selder & Company's linseed oil paints, as a water-repellent impregnation- and polishing agent for wood and porous stone, as well as corrosion protection of metals. Read more on our products under the headings LINSEED OIL PAINTS. PRIMER OIL, FLOOR OIL, FURNITURE OIL, LINSEED VARNISH OIL, STONE OIL, RUSTPROOFING OIL.
The non-drying fatty acids which we separate from the oil in the refining process, are used to make FLOOR SOFT SOAP and STRONG SOFT SOAP.
The remaining residues are utilized for biogas production.