D B Clemons - Casein History

History:
The word "casein" refers to the protein or curd precipitated from milk. You can often find it listed on food labels as the milk ingredient. It is a very strong binder, and is water-resistant when dry, but not entirely waterproof until fully cured; although, it may be varnished with a formaldehyde solution for better permanency. Because the binder comes from milk, its historical use in painting predates oil, and has been found on ancient artifacts. It's still often used for painting wood furniture, and was commonly used on theatre sets before the introduction of synthetic paints. The fact that it has a limited shelf life caused it to fall out of favor for large-scale projects, and for suppliers to store on their shelves. It's a very popular medium for illustrators since its surface is not glossy, so it is easy to photograph.

Usage:
In addition to being an excellent paint binder, it can be used as a size or primer, although not as strong as hide glue and is more porous. It also behaves as an oil and water emulsifier, but some records state it causes the oil to become more yellow with age. It adheres very well to porous material like paper and wood, but dries somewhat brittle so it's not recommended on a flexible surface like stretched canvas, unless mixed with an oil primer. It also works well on stone, and is often used for murals.

Source:
Shiva is perhaps the best known commercial brand of casein. Their best feature is their paints never spoil. I have tubes that are years old, but I'm not certain of their ingredients or preservatives. They also sell a clear emulsion and shellac based varnish. Their color chart is limited, but you can make your own using their emulsion and raw pigment. I like their paint overall, but sometimes it can be rather watery and inconsistent. There's also a brand from Pelican called Plaka that I've not tried, but am led to believe it is a low quality student grade paint.

There is a brand called Iddings, now owned by Rosco, that is made for theatre set painters, and it comes in large cans, or 1 ounce sample jars. These sample jars are a good deal, @ $2 each compared to the $6 price of Shiva, but they will spoil after a few months, and is only sold in a set of 23. Look for online stores that sell theatre supplies. A pint of their white mixed with gysum makes a decent gesso.

Other places sell casein powder where you just add water and a caustic agent like borax to make only what you need. A binder can even be made from fresh milk. You can also mix casein and gouache or watercolors together to extend your color choices, but be aware that some of those paints are not lightfast or permanent.

Handling:
If you've ever used gouache, you'll find casein handles much the same way, especially with its fast drying time. Commercial brands of gouache usually have chalk added as an extender that causes it to dry to a paler shade, which also happens to casein paint when it dries due to its milk base. The "stroke" of the opaque paint is rather short due to the fast drying rate, but it can be watered down quite a bit and still holds very well, and fine details are easy to paint. It also dries to a matte finish. There are differences to gouache, however, outside of the obvious binder component. Mainly, gouache can always be re-activated with water, but casein is more water-resistant when dry and makes a tougher film. Like egg tempera, casein is a good choice for underpainting oils, but it's more absorbent, so an opaque layer should be sealed with a thin coat of bleached de-waxed shellac, or mix in oil to the casein used for underpainting.

Painting Tips and notes:
When painting over a dried layer, it's a good idea to use as little water as possible or else the bottom layer will lift. You can glaze this way or paint over a toned underpainting. Although there's really no "fat over lean" rule here since it dries so quickly, if the paint is applied too thick it tends to cake up, which will crack over time, and underlayers can absorb some of the binder on top. It's better if top layers have more binder in them. The best result comes from not getting it too thick. Instead of painting over an area you don't like, I recommend just wiping it off.

To blend a media like this that dries in seconds, it's best to mix your values on your palette first, and then blend them together on the surface. I like it when the brushstrokes show, so I prefer to do as little blending as possible. The overall surface size I use is not that large, about 18 inches maximum but usually around 1 foot. To paint large opaque strokes you'd have to mix up quite a bit of paint, which would dry too quickly. The brushes I use are rather small, except for washes. You can re-wet the paint on your palette somewhat with water, but after a while it becomes unmanageable. I typically only squeeze out small dabs of a few colors for an isolated area, which is a method I've also adopted for oils.

When painting wet paint over a dried opaque layer, even if it's the same mixture, the fresh paint will turn a shade darker. The solution in that case is to adjust the new paint to a lighter value to match the shift.

Another compatible emulsion is methylcellulose, which is made from wood pulp. The main advantage is it never spoils. It's also a good oil and water emulsion. Sinopia sells 1 pound bags of this called Tylose. A little bit goes a very long way. 1 tablespoon made 4 ounces of medium that's lasted over a year.

Melted beeswax paste (with turpentine or spirits) is compatible with casein paint, and makes for interesting textures.

Always use distilled water when painting since the bacteria in tap water can accelerate the spoilage of casein.

The recipes that include ammonia (instead of lime or borax) need to be used in a properly ventilated area. Shiva paints have a strong odor to them that I suspect is ammonia; although, there's no warning about that on the label. The odor takes a while to dissipate as the paint dries so use with caution. After drying for a few hours the odor is gone. I've used borax to make my own medium, which is easier to find than ammonia carbonate, and it works quite well.

Soft brushes, especially taklon synthetics, work very well with casein. It helps to have a gentle touch if you're overpainting any areas. Even stiff brushes can be used for texturing. Use natural hair brushes sparingly if at all, since the amount of water required here can damage them over time.

Resources:
Shiva "Signa-sein"
Iddings Deep Color
Kama Pigment (check the demo section,)
Sinopia