Casein is an aqueous painting medium, which is made from milk. Its seemingly odd derivation notwithstanding, casein is fast-drying, durable and permanent.
History of Casein
The use of casein dates all the way back to pre-historic times, in which artists used milk (possibly human milk) in their cave-painting mediums. In our own times, both illustrators and fine arts painters once commonly used casein. Its use dwindled, though, after the advent of artificial polymers, such as acrylics. But it never disappeared entirely. And now, like so many other “obsolete” mediums, casein is making a comeback.
Using Casein as an Underpainting for Oils
Casein is a beautiful medium in its own right. Many artists do their paintings entirely with casein but because it’s water-based, it also makes an excellent underpainting for oils. For one thing, it is easier and more expedient to work with than oils. Thomas Hart Benton used egg tempera and oil resin over casein as an underpainting in some of his works. See one such painting here.
- Casein is simpler to correct than oils. And, because each application of paint dries so quickly, casein is more practical than oils when you’re making the fine back-and-forth adjustments of lights and darks while modeling the illusion of three-dimensional forms.
- Casein paint layers, moreover, are absorbent. This makes them receptive to subsequent layers of oil paints. And in the case of the casein emulsions, which I will tell you about later, they even make your paintings look like you did them entirely with oil paints.
- If you like to create textural effects in your paintings, you may particularly find casein underpaintings useful. My mini-portrait of my grandson’s playmate is a case in point. I did the texture of his hair and the cloth of his shirt in casein, during the underpainting stage.
If you would like to experiment with casein underpaintings, you have two kinds to choose from, one of which is called true casein. The word true distinguishes it from paint that based upon casein emulsion. If you decide to go shopping for casein mediums, just remember that the two kinds of casein paint are both called simply casein. This has caused some confusion. Many artists don’t even know that there are two kinds of casein paint. on the market.
True casein paint, like other water-based mediums dries immediately. And, once dry, it becomes a water-impermeable and very durable film. Unused true casein paint, though, has a very short shelf life. It does not stay fresh and will spoil within a few days. And because of this weakness, no one markets true casein in ready-made paint form. Thus, you must instead make it yourself. This is not a serious shortcoming, though. Making your own casein paints is easy.
You can buy the ingredients for true casein paint from Sinopia or from Natural Pigments. Natural Pigments also sells a casein paint-making kit, which contains everything you need—including a selection of dry pigments—to make casein paint. Both of these companies can give you recipes for making true casein paint.
The other type of casein paint is a casein emulsion. (This is medium that many artists have in mind when they think of casein.) Although casein is an aqueous liquid, it contains microscopic droplets of oil. Casein emulsion is a product of the 20th century. These are the tube Shiva caseins that you see in art stores and catalogs. (Shiva is a brand name.) The company Pelikan also markets emulsion casein paints, under the brand name Plaka. Most artists, who work with casein, are probably painting with this type of casein.
You can also make your own casein emulsion paint from dry pigments, by combining them with a casein emulsion medium. Natural Pigments markets a version of its Casein Paint-Making Kit, which includes casein emulsion. Shiva, Lukas and Schmincke also market casein emulsions.
There’s one peculiar characteristic of casein emulsion to be aware of. Although it dries to the touch almost immediately by water evaporation, the oil within it dries by gaseous exchange with the atmosphere. And this “curing” process can take about two weeks, depending upon the atmospheric conditions in your studio.
If you start accumulating layers of paint, without letting it cure enough, subsequent brush strokes will accidentally lift up the previous layers. You can look on the bright side here, though. Emulsion casein, being resoluble, is also reworkable.
Artists, who like to build up layers of casein emulsion and don’t want to wait so long for each layer to cure, often use “isolating varnishes.” Many use PVA (polyvinyl acetate) materials, such as Weldbond Glue, Beva Isolating Varnish, and Berger’s Isolating Spray Varnish, which they sometimes dilute with water. You can likewise use PVA products as an isolating varnish between a casein underpainting and an upper layer of oils. (There’s no scientific evidence that such use of PVA materials is—or is not—archivally sound. The Beva varnish, however, is made specifically for art conservators, who use it to restore paintings.)
Alternatives to the PVAs include shellac, retouch varnish, copal varnish, damar varnish, the alkyd mediums, LeFranc & Bourgeois isolating varnish and Natural Pigments’ Lac Water Varnish. These coatings not only keep previously applied paint from lifting, but they keep the oil paint from sinking into the casein paint as well.
Use Casein Underpaintings in Two Ways
One way is to block out the major forms in your paintings, and then fill in the details with oils. This is an approach preferred by some landscape and still life painters. If you want to paint portraits and/or figures, you can underpaint your fleshtones with old masters-style verdaccios (green underpaintings) and grisailles (gray underpaintings) with casein.
Some Tips for Using Casein Underpaintings
- For one thing, casein is inflexible and brittle. So choose a solid support—such as a panel or hardwood board—for your paintings. If you want to paint on canvas, then use a canvas panel—or mount the canvas to the board yourself.
- You can use a combination of the two kinds of casein, if you would like to do so. But I suggest that you follow the fat-over-lean principle. In other words, you can paint the casein emulsion over the true casein—but not visa versa.
- When working with the emulsion casein, particularly when you have accumulated multiple layers of paint, you can reduce the amount of lifting by working with drier brush strokes. It’s the water that loosens the preceding layers of paint.
- Likewise, if you decide to use an isolating varnish on a casein emulsion underpainting, do not apply it with a brush. The friction from even your slightest brushstrokes can inadvertently pick up the frail layers of casein beneath it. So either spray the varnish on, or lay the painting on its back and spread the varnish liquid around by tilting it.
My best advice
The most important advice that I can give you is to experiment. Take the time to acquaint yourself with casein—and do so before you try to do an actual underpainting with it. Using a casein underpainting is really quite simple. Yet, as with other mediums, you can easily get ahead of yourself. So start small with moderate non-descript swatches of paint, and move on from there.
If you’re a traditional representational artist, don’t leap from your swatch test all the way to full-sized paintings. Limit your focus and work small at the start. If you’re a landscape painter, for example, learn to underpaint one tree, before you try to paint a forest. If you are a portrait artist, then learn to underpaint a nose, a mouth, an eye or an ear, before you try to underpaint an entire face.
Underpainting your oils with casein, can accelerate your painting process considerably, and do so without sacrificing the quality of your work.
A full-time artist for 35 years, Butch Krieger began as a television news artist, specializing in courtroom illustrations. Today he works as a commissioned portrait painter and sculptor, as well as a figure and tromp l’oeil still life painter. A workshop instructor, Krieger has been a contributing editor to The Artist’s Magazine for 13 years. To learn about his latest book, Figure Drawing Studio (Sterling Publishing, 2009), go to www.butchkrieger.com.