Is it true that the
fat-over-lean rule is suspended when using alkyd paints and mediums?
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Grain Elevators, by Carol L. Douglas, is an example of a cold-wax medium painting. I used it to add the rough texture of a beaten down industrial setting to the sky. |
Oil paints are pigments suspended in vegetable oil. These drying oils are most commonly
linseed oil but also may be walnut oil or tung, poppy, or perilla seed oils. They
do not dry by evaporation, but by oxidation. To speed up the drying process, metal
salts are sometimes added.
In my youth, we made our own medium with equal parts
linseed oil, turpentine, damar varnish and a few drops of cobalt drier. After
seeing the condition of some 20th century masterpieces, cracked and
brittle after less than a century, I stopped making my own and started to use commercially-prepared
medium instead.
Alkyd mediums have almost completely taken over the
industrial coating world. They dry more quickly than old-fashioned drying oils.
There are many ways to make an alkyd medium, but they all involve cooking a
vegetable oil with a polyol like glycerine. Before you
consider eating the results, however, alkyds generally have Xylene added to control the
viscosity. Alkyds for decorative painting have extra oil cooked in to lengthen
the oil strands and to make a more durable finish.
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The Sacrifice of Isaac, c.
1527, by Andrea del Sarto, courtesy of the Cleveland Museum of Art, shows a
painting at the pre-glaze point.
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I’m seeing more and more students come to class with alkyd-based
products like Galkyd
or Liquin. I’ve used both
and like them well enough; they don’t feel significantly different from conventional media. But I’m skeptical of replacing something proven with
something unproven to save dry time, which is relatively unimportant in alla prima painting. Classic painting mediums
last for centuries when properly applied.
It’s claimed by some teachers that alkyd media allow you to
ignore the fat-over-lean rule in painting. That’s the principle that higher-oil
paints (i.e., mixed with medium) belong on the top levels, whereas lower-oil
mixes (i.e. cut with turpentine or OMS) belong in the initial underpainting.
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The Sacrifice of Isaac, c.
1522, by Andrea del Sarto, courtesy of the Prado, shows the same subject in
what del Sarto would have called its finished form, after meticulous glazing.
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Pigments affect the dry time of paints as much as the oil
binder does. However, as a general rule, the more oil, the longer it takes for
paint to dry. The less oil, the faster the paint dries, but this produces a
more brittle film. That’s one reaason we use thin layers at the bottom and save the juicy
paint for the top.
There’s been a trend toward painting techniques using
glazing layer after glazing layer of thin pigment dissolved in alkyd media. I’ve
even seen paintings done by laying down layers of alkyd medium and then
painting into that. None of that is
proven technology, and won’t be in our lifetimes. It will take another few
generations before the durability of indiscriminate alkyd glazing is proved.
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Self-portrait, c. 1655,
Rembrandt van Rijn, courtesy Kunsthistorisches Museum. His technique involved painting
impasto passages above transparent ones, or the opposite of glazing.
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Glazing has been used since oil painting was invented. It was
traditionally done by applying transparent colors over an opaque monochromatic
grisaille or colored foundation. That doesn’t mean the masters just
indiscriminately glazed everything. Most passages were painted alla prima, just as we do today. Glazing
was restricted to dynamic passages and fine modulations.
To do it right is very tricky; I’ve never mastered it. It’s
hard to predict how a passage will look when dry. You get no second try at the
underpainting, so if it’s wrong, too bad. And the thickness of the glaze
affects not only the paint’s tonal value, but its surface finish.
Still, pigment suspended in a binder is very beautiful. If
you’re interested in this effect, you might try cold-wax medium
instead. Unlike encaustic, which uses heat to thin the wax, cold-wax medium is whipped
with mineral spirits. It has a milky, soft, appearance. You can sand it, scrape
it, and rework it to your heart’s content, and it’s thoroughly modern in its
final appearance.