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Oils and Alkyds As binders for making paints
Drying oils, especially Linseed Oil, have been known since the earliest recorded times, but 3 things worked against it's adoption as the popular painting medium we know today. Firstly refining techniques were poor and the oil was thick and mucilaginous, secondly artist's were very happy with the primary painting medium of the day which was Encaustic. Seeing the work of modern Encaustic masters like Jasper Johns one can see why, and thirdly the distilling of Turpentine had not been invented yet. It wasn't until the 14th century that the modern day refined Linseed Oil was developed, Turpentine was now available, and it was the Renaissance, artists were ready for a new approach to making art. Oil Painting as we understand it was born. The next 700 years saw new pigments, and new implements like flat brushes but the oil stayed essentially the same until the 1960's when Alkyd Oils were developed for the automotive and industrial paints industry. Those industries have now become almost 100% based on the new Alkyd technology, only artist's still keep the Linseed Oil tradition alive. Alkyds have had a major impact on artist's (so far) in the form of mediums to add to conventional oil paint, but Alkyd paints as such have been slower on the uptake, and the signs are that that will remain the case in the foreseeable future.

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Acrylic binders

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Waxes and natural resins


Cold pressed Linseed oil The best grinding oil
By far the best oil for grinding pigments into it has many advantages. It has a high acid number which imparts desirable qualities. Firstly it is more stable as to color. Just because an oil has a certain color when new and liquid does not mean that it will remain so throughout its life as a dried paint film. Cold Pressed oil seems to be particularly stable in this regard. It also produces a more flexible and durable paint film. When grinding it has superior wetting power. It should be first choice for making paint in the studio. There are two types on the market, distinguished by their origins.

Cold Pressed in a windmill on stone mills
This type is the most like the oil used by the old masters. It is also the least efficient method possible and consequently is the most costly oil. I am only aware of one company selling it Old Holland, which claims to be the oldest paint manufacturer in the world and the only one using the oldest techniques of manufacture. Their Linseed Oil from the windmill is noticeably different from all other oils including the industrially produced Cold Pressed oils.

Industrially Cold Pressed Linseed Oil.
Other brands of Cold Pressed Linseed Oil on the market are noticeably lighter and I have no reason to believe they are in any way inferior to the windmill Cold Pressed oil. It is generally easy to obtain from all major artist's supply stores.

It is important to consider the opinions of Linseed Oil manufacturers as detailed below in the Alkali Refined Linseed Oil section in regard to Cold Pressed oils. They believe that The Alkali Refined is superior and present it to artist's materials manufacturers in that light. The above comments are based purely on the accumulated experience of artist's themselves and is backed up by all major artist's materials authorities such as Ralph Mayer. My own experience supports the excellent qualities of the Cold Pressed oils, and I suspect that the big oil manufacturers are actually relying on information relating to industrial paints and have done little if any research into the actual needs of the economically insignificant artist's paints. There is huge economic benefit to the Linseed oil maker to have the whole world use their Hot Pressed products.


Alkali Refined Linseed Oil Hot Pressed oils
By using heat during oil extraction a far larger portion of oil is extracted from the seed. This process first started in the 19th century and is the industry standard. Most artist's oil colors sold that are ground in Linseed Oil, are ground in Alkali Refined oil. The large oil manufacturers have invested large amounts of money for over a hundred years into research on better methods of oil production and the problems with early Hot Pressed oils were largely overcome by using alkali during manufacture instead of acids for the best grades. They claim that it is superior to the Cold Pressed oils in overall qualities, and they claim to have research that backs the claims. On the other hand that research looks at such 'qualities' as economic viability, ease of manufacture and other parameters that artist's don't often consider as being as important as most other industries do. On the other hand, they are expert in their field. the individual artist must make their decisions on what is the best oil to use based on their needs and factoring in all the arguments both ways.

it is common practice to bleach these oils chemically, but the best grades are bleached using superheated steam and refrigeration and these oils have superior color stability to other Alkali Refined oils. Even so it is a good rule of thumb to assume that the palest versions of the oil will darken more with time, and that the deeper colored oils will change less. so that the end result is similar. Alkali Refined Linseed Oil should be regarded as second choice, for use when Cold Pressed is unavailable.


Sun Bleached Linseed Oil An old process
The old masters often used this oil and it is a refining process that can be carried out in the studio by the artist or purchased as it is commonly available still, although there is no guarantee that the purchased product is made from Cold Pressed oil, and in fact is likely not to be. While it has been long used it is believed to produce an oil with similar properties to Blown Oil (see below) including its defects. The sun bleaching process increases the oil's drying speed and leveling qualities, but also creates such undesirable qualities as to reduce its wetting abilities and otherwise render it less desirable for grinding paint. Its use should be restricted to use in painting mediums and varnishes, and for glazing where the underlying layers are well dry.

To make Sun Bleached Linseed Oil mix it with water (salt or fresh) about 50 / 50 and shake the 2 together in a jar then expose to sunlight for several weeks. It needs to be covered so that dust is excluded but air it admitted. Too much air thickens the oil too much. The time for bleaching varies according to season and location. Putting a little clean sand in the mix at the beginning to help promote the settling of impurities, and the oil will require filtering at the end of the process. Separator funnels can be obtained from laboratory supply firms for separating the oil and water at the end. Do not bleach too much as it is possible to bleach to a point where the oil will eventually revert to a darker color than it started as. The optimum bleached color is a light golden color.
 


Hardware store Linseed Oil Bad news oil
Linseed oil sold in hardware stores is intended to be used for treating wood and other applications that do not involve color permanence. Low price is an important consideration as this oil is often used by the gallon, and the low price is attractive to poor artist's. it is advisable to resist the temptation of price as these oils have numerous defects for artist's use. There are 3 main types that are available:

Raw Linseed Oil
This is Hot Pressed oil which is warmed and then simply left to stand for a period while the sediments (called 'foots') settle. It is a dark oil, cheap to make which has only one advantage, that of durability which makes it popular for treating bare timber and making industrial coatings. It should never be used by any artist wanting their paintings to last as it will darken with time.

Boiled Oil
This is Raw Oil that has driers added. The better grades are heated as well to thicken the oil. The driers make a poor oil even worse in terms of permanency of artist's paints. Unwise to use.

Blown Oil
This oil is polymerized by blowing air through the oil. This process thickens the oil which is useful for many industrial purposes, but can have a poor result if used for making artist's colors.


Stand Oil Great oil, but not for paint making
Stand oil is probably the least yellowing of the Linseed oils but that is not enough to make this a good oil for grinding pigments in. It has excellent leveling properties, which means it doesn't leave brush marks, and is slow drying. It will impart these properties to any paint made with it. Use it for glazing, where it is the perfect oil, and never use it to make paint.

Poppy Oil The  non yellowing alternative
Often used, especially for whites and other light colors Poppy Oil has never the less always played second fiddle to Linseed oil for good reason. While it is naturally a pale yellow or is almost colorless, it has other problems. it has a far greater tendency to crack than Linseed Oil, and is slower drying. Only one major manufacturer grinds all of their colors in Poppy oil but many others grind the light colors in Poppy as the light colored oil makes the paint look brighter straight from the tube. manufacturers also like the ability of Poppy oil to produce buttery paint easily.

On the other hand the long term durability of these paints is not as good as Linseed Oil paints and while they start very pale. Poppy oils are known to yellow with age, although perhaps a little less so than Linseed Oil. it is the drying speed and lack of long term flexibility that are of greater concern however, and painting with oil paints ground in Poppy Oil requires careful attention to sound traditional painting practices to ensure maximum longevity of the work. With such care however Poppy Oil can be used with confidence as a useful alternative to Linseed Oil.

Nut Oil Made from English Walnut kernels
In use from the earliest times of Oil Paint usage this was the favored oil of Leonardo da Vinci. Despite this recommendation, and the fact that this was a commonly used oil in the early times and has been argued to be superior to Poppy Oil, this oil is not so commonly used today. This may be due to high cost which has prevented it being used in industry which has usually been the driving force for research and popularization of other products. it has similar properties to Poppy Oil, but has the advantage of faster drying. Overall, however, it is considered inferior to Linseed Oil in terms of long term durability, although approximately the equal of Poppy Oil. In that case its faster drying would suggest it would be used more than it is, and perhaps unfamiliarity as well as cost and availability are the factors at work here.


Hempseed Oil Historic interest only
Hempseed Oil was used in the early days of Oil Painting as an alternative to Linseed Oil. it has properties similar to, but inferior to Poppy Oil. it should not be considered for permanent painting.


Safflower Oil Becoming more common
Some of the largest artist's materials manufacturers are using this oil to grind the whites and some light colors and blues. it is used in industrial paints as it has a good reputation as non yellowing. It is a common ingredient in Alkyd Resin paints and is used in large quantities industrially. it is generally considered inferior to Linseed Oil in terms of long term durability as the paint film is likely to become brittle with time.

Sunflower Oil Another industrial product
Sunflower Oil is similar to Hempseed Oil in general properties and is sometimes used as a Linseed Oil substitute, but not by artist's expecting  to make permanent paints. Often used, especially for whites and other light colors Poppy Oil has never the less always played second fiddle to Linseed oil for good reason. While it is naturally a pale yellow or is almost colorless, it has other problems. it has a far greater tendency to crack than Linseed Oil, and is slower drying. Only one major manufacturer grinds all of their colors in Poppy oil but many others grind the light colors in Poppy as the light colored oil makes the paint look brighter straight from the tube. manufacturers also like the ability of Poppy oil to produce buttery paint easily.

On the other hand the long term durability of these paints is not as good as Linseed Oil paints and while they start very pale. Poppy oils are known to yellow with age, although perhaps a little less so than Linseed Oil. it is the drying speed and lack of long term flexibility that are of greater concern however, and painting with oil paints ground in Poppy Oil requires careful attention to sound traditional painting practices to ensure maximum longevity of the work. With such care however Poppy Oil can be used with confidence as a useful alternative to Linseed Oil.

Alkyd Oil-modified Resins Fast drying alternatives
Alkyd oil-modified resins are unusual in this list in that the oil becomes an integral part of the resin molecule as a result of the manufacturing process. The oils used can be various, Safflower and soya are very common, but it can also be made with Linseed Oil and this Linseed Oil version is not surprisingly, the most durable. It has the disadvantage as with the traditional form of the oil that it is likely to yellow more however. Alkyd Oil-modified Resins have unique properties that have seen them almost totally replace traditional Linseed Oil as the primary house painting and industrial paint oil. Their most obvious characteristic, that of extremely rapid drying has resulted in a less rapid acceptance in the fine arts, where slow drying in oil is often seen as an advantage. However they have become a popular painting medium where the advantages of Alkyd can be easily balanced with the advantages of traditional oils for a compromise paint that suits many artist's.

Utilizing Alkyds as a basic material for grinding pigments is best left to the experts but there is no reason why grinding colors into the prepared Alkyd mediums sold in art store cannot be experimented with. There are several available with various properties but as a guide I might mention Liquin and Oleopasto both made by Winsor and Newton as examples of a thicker and thinner Alkyd medium that might be a good starting point.


References
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Cennini, C d'A,    The Craftsman's Handbook.    1437 (Dover)
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Eastlake, Sir C L,    Materials For A History Of Oil Painting,    1847 (Dover)
Feller, R L,    Artists Pigments    1986 (National Gallery Of Art / Cambridge University)
Gottsegen, M D,    A Manual Of Painting Materials And Techniques,    1987 (Harper & Row)
Maire, F,    Colors: What They Are And What To Expect Of Them,    1910 (Drake)
Mayer, R,   The Artists Handbook Of Materials And Techniques,    fifth edition 1991  (Faber & Faber)
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Parkhurst, D B,    The Painter In Oil   1898 (Lothrop, Lee & Shepard)
Patton, T C,    Pigment Handbook,    1973 (Wiley)
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Various,    Encyclopedia Britannica,    fifteenth edition 1981  (Encyclopeadia Britannica, Inc)
Various,    Paint And Painting,   1982,  (Winsor & Newton / The Tate Gallery)
Various,    The Artist's Colourmen's Story,    1984 (Winsor & Newton)
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