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Category: alkyd medium

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Monday Morning Art School: How to use medium

The actual process is simple, but it has to be done right to prevent chalkiness or cracking.
The Farm at Olana, by Carol L. Douglas
“How should I treat older, unvarnished paintings that have become chalky?” a reader asked me. “And for that matter, what kind of varnish do you recommend?”
Chalky paintings are best revived with varnish. My personal preference is Winsor and Newton Artist’s Matt Varnish. It’s easily removable by a conservator, provides UV protection, and it doesn’t shine. (If you want more reflection, they make both gloss and satin finishes.) As with all varnishes, it shouldn’t be applied for a year after the painting has been finished, and it should never be used as a painting medium.
But learning to use medium properly is a better protection against chalkiness. (If you’re new to oil painting, consult my basic rules of oil painting.)
Mamaroneck River, by Carol L. Douglas, in its finished form right before it went on the auction block.
There are several families of oil painting mediums out there:
  • Traditional mediumsare made from a slow-drying oil (poppy, linseed, etc.) a resin, and a solvent, sometimes with a siccative like Cobalt Drier added to improve the drying time.
  • Alkyd mediums are made with a slow-drying oil reacted with an alcohol and an acid. They dry faster, making them suitable for multiple glaze layers, but they carry less pigment. They should never be used on top of traditional oil mediums.
  • Solvent-free mediumsdo not include any petroleum distillates. All unmixed slow-drying painting oils are inherently solvent-free, being plant-based.
  • Wax based mediums include cold wax and encaustic.

Mamaroneck River, when the second layer was done but the top layer hadn’t been started.
For field painting, I prefer a traditional medium: Grumbacher’s Oil Painting Medium II. It retards the drying time and allows me to work wet-on-wet longer. In particularly dreary conditions, I’ll use their Medium III, which has a drier. For studio work, I sometimes use their Medium II, because it dries to a matte finish. I buy this brand because I prefer a very thin medium. There are many good brands out there, and I would trust any medium made by a reputable paint house.
Grain elevators, Buffalo, by Carol L. Douglas is an example of a cold-wax medium painting. It gives tremendous latitude in effects.
Back in the last millennium, there was a popular recipe of linseed oil, turpentine, Damar varnish and a few drops of Cobalt drier. I stopped making it when I realized that so many 20th century masterpieces were degrading terribly. Chemists understand chemistry better than painters do.
The drawing layer is always done with solvent, whether in the studio or in the field. That’s Sandy Quang, back when she was my studio assistant.
Neither medium nor solvent is a substitute for good, open paint. If you’re poking a skin off your paint and extending it with solvent, it’s time to clean your palette and get new paints out.
The actual process for using medium in alla prima painting is simple: fat over lean. Your first layer—where you’re drawing the picture on the canvas, called the underpainting—is cut with a small amount of solvent only. Use too much and you’ll have muck above. Your middle layer should be as close to pure paint as you can get, applied thinly. Your top layer should be paint with a small amount of medium, and here’s where you can get as impasto as you want.
Clip this and paste it in your pochade box until it’s a habit.
Medium doesn’t belong in the bottom layers of a painting. The more oil in a layer, the longer the binder takes to oxidize. This keeps paints brighter and more flexible. However, oil also retards drying. Using too much in underpainting will result in a cracked and crazed surface over time.
Use too much medium and you’ll have a soup that dries to a plasticky finish. Use too little, and the paint will drag as you paint and cloud as it dries. I generally just touch the tip of my brush to the medium before mixing it into a brushstroke’s worth of paint.
This traditional method is tremendously variable and gives great control. Practice it.
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There’s nothing new under the sun, and that includes glazing

Is it true that the fat-over-lean rule is suspended when using alkyd paints and mediums?

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.
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.
I’m seeing more and more students come to class with alkyd-based products like Galkydor 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. 
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.
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.
Self-portrait, c. 1655, Rembrandt van Rijn, courtesy Kunsthistorisches Museum. His technique involved painting impasto passages above transparent ones, or the opposite of glazing.
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 mediuminstead. 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.