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| This picture is in the public domain. |
By Jim Hingst
Pressed from the seeds of the flax plant,
linseed oil has been used as a paint binder or resin by painters for hundreds
of years. In fact, traditionally oil paint in the day of Jan Van Eyck was
typically not much more than linseed oil and pigment. A few companies, such as Natural Pigments manufacturer of the Rublev Colors brand, still produce paints the way that they were made prior to the Industrial Revolution.
Most modern paints, by
comparison, are comprised of many more ingredients, including fillers, extenders
and driers. For a full explanation of the differences between paints made the way that the Old Masters made paint and modern artists colors, read my story Why Paint and Pigments Degrade.
linseed oil has been used as a paint binder or resin by painters for hundreds
of years. In fact, traditionally oil paint in the day of Jan Van Eyck was
typically not much more than linseed oil and pigment. A few companies, such as Natural Pigments manufacturer of the Rublev Colors brand, still produce paints the way that they were made prior to the Industrial Revolution.
Most modern paints, by
comparison, are comprised of many more ingredients, including fillers, extenders
and driers. For a full explanation of the differences between paints made the way that the Old Masters made paint and modern artists colors, read my story Why Paint and Pigments Degrade.
In addition to linseed oil, poppy oil, safflower oil and walnut
oil are classified as drying oils. What
that means is that after it is exposed to oxygen, it dries and hardens. Not all
oils react this way in the presence of oxygen. Some oils just thicken and
become sticky.
oil are classified as drying oils. What
that means is that after it is exposed to oxygen, it dries and hardens. Not all
oils react this way in the presence of oxygen. Some oils just thicken and
become sticky.
For a detailed explanation of the different types of drying oils used in oil painting read my article The Facts about Drying Oils for Painting.
As the linseed oil oxidizes, the molecules begin to polymerize, producing an
exothermic reaction, which means that they generate heat. Not to worry, it is
highly unlikely that your painting will burst into flames. On the other hand,
you should not be careless in how you discard your oil soaked rags. As rare as it may be, a pile of oily rags thrown
away in a corrugated box can release enough energy to cause a spontaneous
combustion. The safer practice is to dry the rags outside or, better yet, dispose of oily rags in a metal safety can
with a foot operated cover.
exothermic reaction, which means that they generate heat. Not to worry, it is
highly unlikely that your painting will burst into flames. On the other hand,
you should not be careless in how you discard your oil soaked rags. As rare as it may be, a pile of oily rags thrown
away in a corrugated box can release enough energy to cause a spontaneous
combustion. The safer practice is to dry the rags outside or, better yet, dispose of oily rags in a metal safety can
with a foot operated cover.
 |
| Metal Safety Can |
● Self-closing cover opens easily.
● Excellent for disposing rags and toweling soaked with solvents,
thinners and linseed oil.
thinners and linseed oil.
● Elevated base allows good air circulation to disperse heat buildup. Reduces
moisture collection at the bottom of the can that can cause rusting.
moisture collection at the bottom of the can that can cause rusting.
Linseed oil consists of different types of triglycerides. These complex compounds
are comprised of one molecule of glycerol and three molecules of a fatty acid. Glycerol
serves as the backbone of a triglyceride by connecting these fats together. In paint formulations, these large polymer molecules crosslink and mesh together, binding the particles of pigment in the paint film. Oils, which create more crosslinks, are tougher and last longer.
are comprised of one molecule of glycerol and three molecules of a fatty acid. Glycerol
serves as the backbone of a triglyceride by connecting these fats together. In paint formulations, these large polymer molecules crosslink and mesh together, binding the particles of pigment in the paint film. Oils, which create more crosslinks, are tougher and last longer.
Processing of Linseed Oil
Linseed oil used for making oil paint is extracted from the flax seeds using a number of different manufacturing processes. Cheaper oil is produced using a solvent to dissolve the oil from
the seeds. Oil is also pressed from the seeds. In one of these pressing processes, the seeds are first
heated and pressed while they are hot. In
another method, the seeds are cold pressed. The oil resulting from cold
pressing is clearer than the oil which is produced from hot pressing.
the seeds. Oil is also pressed from the seeds. In one of these pressing processes, the seeds are first
heated and pressed while they are hot. In
another method, the seeds are cold pressed. The oil resulting from cold
pressing is clearer than the oil which is produced from hot pressing.
The cold pressing process produces oil that is clearer and less viscous
than the other processes. However, extracting oil in this manner is much less
efficient and more costly.
than the other processes. However, extracting oil in this manner is much less
efficient and more costly.
After the oil is extracted, one method to clarify and purify it is to expose
it to light and store it at elevated temperatures. Processing in this manner
bleaches the oil and causes the impurities to congeal. Other methods to purify
the oil include boiling it in alcohol or filtering it.
it to light and store it at elevated temperatures. Processing in this manner
bleaches the oil and causes the impurities to congeal. Other methods to purify
the oil include boiling it in alcohol or filtering it.
Oil exposed to heat will absorb some oxygen, which allows it to harden
faster than oil, which has not been heated. Nevertheless, however the oil is
processed, the end result is that it oxidizes more readily and consequently
hardens faster.
faster than oil, which has not been heated. Nevertheless, however the oil is
processed, the end result is that it oxidizes more readily and consequently
hardens faster.
Cold Pressed Linseed Oil
● Produced
from pressing flax seeds without using heat or chemicals.
from pressing flax seeds without using heat or chemicals.
● Added
to oil paint to enhance gloss of colors.
to oil paint to enhance gloss of colors.
● Increases
the brilliance and transparency of colors.
the brilliance and transparency of colors.
● An
alternative to turpentine and mineral spirits for thinning oil paints.
alternative to turpentine and mineral spirits for thinning oil paints.
Grumbacher Sun-Thickened Linseed Oil Medium for Oil Paintings
● Add
directly to oil paint to make colors glossy and fluid
directly to oil paint to make colors glossy and fluid
● Heavier
in body than traditional linseed oil
in body than traditional linseed oil
● Extremely
flexible with excellent resistance to yellowing
flexible with excellent resistance to yellowing
Gamblin 8.5 Oz Refined Linseed Oil (ANG06008)
● Light
and pure as industrially produced linseed oil can be made.
and pure as industrially produced linseed oil can be made.
● Use
in moderation to thin oils or as an ingredient in traditional painting mediums.
in moderation to thin oils or as an ingredient in traditional painting mediums.
● Increases
the brilliance and transparency of oil colors.
the brilliance and transparency of oil colors.
3M Gamblin Stand Linseed Oil 8 Oz (G08008)
● Heavy-bodied linseed oil, polymerized by heating
● High
viscosity – requires thinning
viscosity – requires thinning
● Moderate
drying time
drying time
● Leaves
a glossy enamel-like finish
a glossy enamel-like finish
How Linseed Oil Changes as It Oxidizes
As the oil absorbs oxygen in the polymerization process, it
initially gains weight. It also emits carbon dioxide and other VOCs. Over time
the film can lose some of its weight gain as smaller molecules migrate out of
it. What is also important is that in the curing process, not all of the oil
oxidizes. This unreacted portion provides the cured paint film with flexibility. However,
over time, as migration continues, the film can gradually embrittle and crack.
Regardless of the type of oil binder used in a paint’s composition, all
oil paints dry relatively slowly. Paints utilizing linseed oil as a medium actually dry much faster than
other paints that use safflower oil, poppy oil or walnut oil as their resin.
This is one reason that linseed oil is a popular binder for oil paints. Other
reasons include the toughness of the paint film, long term durability, good
gloss level and transparency.
oil paints dry relatively slowly. Paints utilizing linseed oil as a medium actually dry much faster than
other paints that use safflower oil, poppy oil or walnut oil as their resin.
This is one reason that linseed oil is a popular binder for oil paints. Other
reasons include the toughness of the paint film, long term durability, good
gloss level and transparency.
The Effect of Pigments on Drying
Some paints dry more slowly than others depending on the type of
pigments used to make it. The reason is that different pigments affect the rate
at which a drying oil cures. Many pigments include metal
ions, such as cadmium, lead and cobalt. Some these metal ions can affect the oxidation
of linseed oil and the formation of a paint film. Some metal also promote the formation of crosslinks between molecules. The speed at which the metallic ion accelerates the curing of the drying oil largely depends on how soluble it is.
Flake
white, for example, which is made from lead carbonate, has a strong catalytic effect on speed at which linseed oil cures. For this reason, it should surprise no one that this paint dries faster than either titanium white
or zinc white, which dries at the slowest rate of all three whites. To learn about the advantages and disadvantages of the different types of white paints read What You Must Know About White Oil Paint and White Lead Oil Paint.
pigments used to make it. The reason is that different pigments affect the rate
at which a drying oil cures. Many pigments include metal
ions, such as cadmium, lead and cobalt. Some these metal ions can affect the oxidation
of linseed oil and the formation of a paint film. Some metal also promote the formation of crosslinks between molecules. The speed at which the metallic ion accelerates the curing of the drying oil largely depends on how soluble it is.
Flake
white, for example, which is made from lead carbonate, has a strong catalytic effect on speed at which linseed oil cures. For this reason, it should surprise no one that this paint dries faster than either titanium white
or zinc white, which dries at the slowest rate of all three whites. To learn about the advantages and disadvantages of the different types of white paints read What You Must Know About White Oil Paint and White Lead Oil Paint.
In
another example, some raw umber contains a significant amount of manganese
dioxide. As the manganese ions dissolve in the linseed oil, it speeds up the
drying time of the paint.
another example, some raw umber contains a significant amount of manganese
dioxide. As the manganese ions dissolve in the linseed oil, it speeds up the
drying time of the paint.
To accelerate the oxidation of the oil in paint, an artist can add chemical driers to the paint. Some
chemists distinguish between metallic driers that accelerate the oxidation of a
drying oil and those that promote the polymerization process. Those that affect
oxidation include cobalt, manganese and lead. The auxiliary driers that
accelerate polymerization include zinc, potassium, lithium and sodium. While the addition of a siccative can hasten the drying
process, it can also result in undesirable effects including darkening of the
colors and cracking.
chemists distinguish between metallic driers that accelerate the oxidation of a
drying oil and those that promote the polymerization process. Those that affect
oxidation include cobalt, manganese and lead. The auxiliary driers that
accelerate polymerization include zinc, potassium, lithium and sodium. While the addition of a siccative can hasten the drying
process, it can also result in undesirable effects including darkening of the
colors and cracking.
For more information about driers read Paint Driers.
Do You Have Questions or Comments?
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About Jim Hingst: Sign business authority on vehicle wraps, vinyl graphics, screen printing, marketing, sales, gold leaf, woodcarving and painting.
After fourteen years as Business Development Manager at RTape, Jim Hingst retired. He was involved in many facets of the company’s business, including marketing, sales, product development and technical service.
Hingst began his career 42 years ago in the graphic arts field creating and producing advertising and promotional materials for a large test equipment manufacturer. Working for offset printers, large format screen printers, vinyl film manufacturers, and application tape companies, his experience included estimating, production planning, purchasing and production art, as well as sales and marketing. In his capacity as a salesman, Hingst was recognized with numerous sales achievement awards.
Drawing on his experience in production and as graphics installation subcontractor, Hingst provided the industry with practical advice, publishing more than 150 articles for publications, such as Signs Canada, SignCraft, Signs of the Times, Screen Printing, Sign and Digital Graphics and Sign Builder Illustrated. He also posted more than 500 stories on his blog (hingstssignpost.blogspot.com). In 2007 Hingst’s book, Vinyl Sign Techniques, was published. Vinyl Sign Techniques is available at sign supply distributors and at Amazon.
© Jim Hingst 2018
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