Many beginning painters ask about mediums for oil painting. What are they, which should I use, and so on. Mediums in oil painting can be used to improve handling, allow thicker or thinner application of paint, add crispness to strokes, change appearance, and more. In the past a master would have imparted this information to an apprentice along with his recipes for making the materials needed. The apprentice spent years assimilating and practicing, most eventually passing the torch to a new generation. Today the best one can do, absent an atelier or school, is to scour the Internet for information. Unfortunately of course, that means finding a way to separate good information from less useful. This post is intended to give the reader my own thoughts and experience with oil painting mediums. Others may give a different viewpoint.
There is a myth that recipes and methods owned by the masters of the past were lost, but more likely their history is similar to nearly everything in life--that is information about oil painting has faded to near-obscurity (in certain cases) and is now being explored with more interest. During the latter part of the 20th century there seems to have been less discussion and use of mediums but now their usage may be on the upswing. Judicious use of mediums can help a painter-craftsman to add visual interest and intellectual luster to oil paintings. You can make your brushstrokes more or less obvious, for example. A medium that levels the paint strokes and dries slowly will look glossy when dry; a medium containing a thickener can give a soft, matte finish (wax medium) and preserve brush marks.
So do we need to use mediums in our paintings? The answer depends on the individual, so far as I can see. Many painters add nothing to their tube paint; others add only solvent or only linseed oil or linseed oil thinned with mineral spirits or turpentine. The results in such work are good and longevity seems likely. In effect the painter often varies the oil to thinner ratio so that top layers have a bit more oil (fat over lean). In contrast, some painters mix medium into tube paint before using; some dip the brush into medium first then into paint (or vice versa) before laying in each stroke. But mediums are certainly not required. When using a medium of any sort, probably the most important caution is to use the material sparingly. There was a hair product years ago with the slogan, "A little dab'll do ya," which is a great motto for the use of mediums too. The minimum amount needed to achieve the desired effect is all one should use; using too much guarantees problems. As a rule of thumb, the total medium added should be less than ten percent of the paint volume--and much less most of the time.
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Other mediums include various kinds of altered linseed oil, each of which some artists swear by. Basic linseed oil can be treated in various ways, including sun-thickening or sun-bleaching, washing the oil, and heating it, among others. A special kind of heated linseed oil is known as stand oil. Stand oil is linseed oil that has been super-heated to more than 300 degrees C in a vacuum, allowing the oil to polymerize somewhat; it becomes quite thick. Stand oil and solvent make a very pleasant general medium. Sun-thickened oils are similarly thick and are used in similar ways. Another drying oil could be substituted for linseed, notably walnut oil. So mediums come in all kinds of recipes. Many companies market "oil painting medium," most of which likely contain linseed oil, a small amount of a resin, and solvent.
Here are three recipes that use the same ingredients in different combinations and proportions (odorless mineral spirits can be substituted for turpentine):
Note that the author has only tried the basic turpentine, dammar and linseed oil version. The addition of cobalt drier is completely unknown to me. This recipe in all of its incarnations can be made in the studio or purchased in various commercial forms.
One medium that interest many has come in for enormous criticism is megilp (there are other spellings),or Maroger medium. There is a lot of confusing information and controversy available online about this particular concoction as well. "Discovered" and popularized by Jacques Maroger (1884–1962) an oil painter, teacher, and former director the laboratory at the Louvre, the medium is roundly derided by some and routinely used by others. Maroger medium has actually been known under various names since the heyday of Venetian and Dutch painting. Like other mediums recipes Maroger medium (or megilp) come in different proportions. But regardless, Maroger medium always contains leaded oil (also known as "black oil") and mastic varnish. The leaded oil may be cooked--heated--for various time periods, then combined with a highly-saturated mastic varnish (mastic resin and solvent). The result gels but liquifies when manipulated. This medium (and others too) is applied as a very thin layer (called a "couch") which makes the surface accept paint more smoothly. The colors appear brighter, too. Another way painters use the medium is by dipping the tip of the brush into it before adding paint.
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There are other mediums available, notably alkyd-based, but I've no experience with alkyd paint or mediums.
So in summary, here is my strategy in using mediums:
- Mediums aren't required. Use them to improve handling and appearance.
- Mediums must be used sparingly. Doing otherwise is courting disaster.
- Simple is better: linseed oil alone, thinned, is quite serviceable.
- Mix into the paint piles or use from a cup by dipping.
- Consider using a very thin couch of linseed oil. It makes painting a pleasure.
Other posts regarding materials: