Linseed oil is a mixture of fatty acids, proteins, waxes and antioxidants. Of these, only the fatty acids have the desired properties for linseed-oil paints and impregnation oils. All other components of the linseed oil worsen the end result.
The multisaturated fatty acids oxidate with the oxygen in the air and create molecular chains - polymers - which are useless as nourishment for living organisms and therefore have a practically unlimited durability. We remove all other components by refining, and keep the multisaturated fatty acids. We pre-oxidate them to varying viscosities and hardening times depending on their desired application. The longer the oxidation proceeds, the thicker the oil gets, and the faster it is fully oxidised, i.e., hardened/dried into an elastic polymer called linoxyn. These fatty acids penetrate dry surfaces and are permanently attached when they harden into linoxine, which is water-repelling and insensitive to fats, petroleum products, salts and mild acids.
Linseed oil was refined in a comparable way, to create the best linseed oil paints and linseed oils, until the mid-20th century. The process was very time-consuming, and quickly forgotten about once the synthetic paints made their breakthrough.
The chemistry of drying oils
Linseed oil contains two drying fatty acids: linoleic acid, whose molecules contain two double-binding between oxygen atoms, and linolenic acid, containing two. These can create molecular chains of a practically unlimited length, i.e., be polymerised, by oxidation.
For instance, an oxygen atom in the air bridges two fatty acid molecules by attaching to one of the bindings in a double-binding with oxygen atoms in either end. Thereby the fatty acid molecules are united into a bigger molecule. Since the linoleic acid can bridge two other fatty acid molecules and the linolenic acid can bridge into three, the polymerisation can continue until giant molecules have formed. The end result is an elastic polymer called linoxyn.
Linseed oil also contains oleic acid, whose molecules contain a double-binding between oxygen atoms. It can only build one oxygen bridge onto another fatty acid molecule, and therefore can become part of giant linoleic and linolenic molecules, but not form giant molecules on its own.
All other components of the linseed oil mess up the drying, colour durability, durability and mould resistance in oils and paints. Read more on this below.
Components harmful to linseed oil paints and impregnation oils
The tendency of linoleic and linolenic acids to polymerise with oxygen threatens the growability of the seed. Therefore, the linseed creates antioxidants, primarily tocopherol (vitamin E).
Unless the antioxidants are removed, the linseed oil paint takes a week or longer to dry, often incompletely. This problem can be solved by adding a desiccate, usually cobolt zirconium carboxylate. This makes the oil not dry all the way through but just on the surface: “skin-drying”. Therefore 2-butanone oxime is often added to combat the drying on the surface.
Adding chemicals such as these have varying results. 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 warm seasons, and that linseed-oil paint dries much slower than alkyd paints (read more on this below).
Selder & Co. have 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 photo-chromaticity of linseed oil, i.e., it yellows in darkness and fades in a few hours when exposed to light.
Selder & Co. have solved the problem of permanent yellowing by removing the beta-carotene.
Saturated fatty acids
Linseed oil contains two saturated fatty acids: stearine and palmitid acid. These do not dry, as they do not contain double-bindings between oxygen atoms. Instead, they go rancid, react with water and nourish micro-organisms. Therefore, manufacturers of linseed-oil paints often add mouldicide. Additionally, stearine and palmitid acid breaks down quickly, which leads to degradation of the binder and exposure of the bare pigments, which in turn leads to “chalking” paint. Linseed oil paint work manuals often state that the paint has to be “freshened” from time to time.
When oil, varnish or paint containing these fatty acids are exposed to moisture, white spots appear on the surface (oil/water emulsions) that need to be wiped off.
Selder & Co. have solved this problem by removing these fatty acids.
Waxes on the seed-coating turn into a sticky gel when exposed to water. That is how linseeds spread: the sticky seeds attach themselves to passing animals. When oils, varnishes or paints that contain these waxes are exposed to moisture, white gel spots that require wiping appear on the surface.
Selder & Co. have solved this problem by removing the waxes.
Proteins provide excellent nourishment for all living organisms and dissolve easily. This is the most important factor in the bio-degradation of linseed oil.
Selder & Co. have solved this problem by removing the proteins.
Alkyd oil paints = polyester = a plastic
To quote from The Swedish National Heritage Board, Materials guide (our translation):
“For a time, alkyd-oil paints were used for restorations, replacing linseed oil paints. But although the drying times were shorter and they were more durable [NOTE: compared to linseed oil paints made from UNREFINED linseed oil - i.e., this does NOT pertain to Selder linseed oil paints!], the alkyd paints had difficulty meeting the required standards for adequate penetration, elasticity and an authentic appearance during aging and degradation.”
Selder & Co. linseed-oil paints provide a better alternative.
By applying modern processing techniques to the old art of refining, we produce clean multisaturated oils. Pumps, containers, pipes and process vessels are as far as physically possible made from stainless and/or acid-resistent steel. This allows us to maintain the high production hygiene necessary to make products of a high and consistent quality. The raw materials are introduced to the process via PLC-controlled scales and automated valves, thereby ensuring the exact amounts added at exactly the right times for a perfect and consistent end result.
The refined linseed oil is used as the sole binder in Selder & Co's linseed oil paints as well as water-repelling impregnation and varnishing products for wood and porous stone, concrete dust-binding and for anti-corrosion products for metals. Read more on our product under the headings PRIMER OIL, FLOOR OIL, FURNITURE OIL, LINSEED VARNISH OIL, STONE OIL, RUSTPROOFING OIL.
The non-drying fatty acids parted from the oil when refining are used to make FLOOR SOFT SOAP and STRONG SOFT SOAP.
The remaining leftovers are utilised for biogas production.