Casein FAQ

Richeson Casein: Frequently Asked Questions


What was Casein originally used for?

Paint made with Casein was originally used in a gouache manner, simply opaque or somewhat impasto for mural paintings and frescoes, but the strength of Casein as an adhesive made that its primary function. Recipes for the use of adhesives made from Casein, or curd, date back to the 11th century.

The perfection of tubed Casein colors during the early 1930s provided artists with the perfect complement: a water-soluble paint that could be used in place of or in conjunction with oil colors. In the 1930s, buildings were painted with Casein, and during World War II it was used for camouflage. Ready-to-use Casein wall paints were popular during the 1940s and 50s. No other media has been so versatile for so long.


What are the advantages of Casein?

Casein differs from other media, yet it shares many of the same characteristics, which make it a very versatile medium that lends itself to many techniques. Casein has the wash capabilities of watercolor, the smooth opacity of tempera and gouache, and the richer textures of oils and acrylics. It dries quickly to a velvety, matte finish and over time, it becomes resistant to moisture. Unlike oils, Casein is a clean, water-soluble medium requiring no strong solvents. As it dries quickly, it is possible to lay on a glaze and move on to the next stage within a few hours instead of waiting for days, or even months, for oil glazes over oil to dry. Acrylics can become gummy and resinous unless you buy retarders and mediums. It can also gum up your brushes, making fine detail hard to achieve. Brushes dipped in Casein keep their finesse, producing clear, crisp lines.

Can Casein be "corrected?"

Casein is correctable. Rub or scrub the area with a damp cloth, paintbrush, or eraser. Use a mixture of ammonia and water (one part ammonia to nine parts water) if it has partially cured.

What if I want a color not available in the Richeson Casein line?

You can mix Shiva Casein Emulsion with powdered pigments: Spray some water on your palette and scoop out the pigment with a palette knife. Mix thoroughly into a paste and add a few drops of Shiva Casein Emulsion. Mix again, and you're ready to paint.

Is Casein archival?

Yes. Properly done and with a protective varnish, Caseins can last longer than oils, especially oils on canvas. They will not crack or yellow.


What surfaces may be used with Casein?

Casein may be applied to any rigid non-oily surface such as canvas panels, gessoed painting panels, illustration boards, heavy watercolor paper, wood panels, or masonite. Casein can also be applied to metal, sheetrock, cement, plaster, wet or dry lime walls, and for decorative purposes on glass.

Can Casein be used on stretched canvas?

Yes, but it must be painted thinly because Casein can crack if applied too thickly on a flexible surface. If you would like to paint thickly and would still like to paint on canvas, mount the canvas or linen on masonite, and prime the canvas with PVA, glue, or acrylic gesso.

What kind of watercolor paper is recommended?

Heavy, rigid paper, 300lbs. and up works best. The heavier weights will not ripple when a wash is applied.

What grounds can Casein be used on?

Rabbit skin glue, PVA, glue size, and acrylic gesso. Just make sure there is no oil in/on the grounds.

Can Casein be used for painting a mural?

Yes, but only indoor murals. For outdoor murals, you'll have to use specialty paints. Although Casein becomes resistant to water over time, the elements would take their toll.

Can Casein be used for painting furniture or walls?

For furniture, clean the wood and prep it with PVA glue, gesso, or a primer/sealer. For walls, prime with gesso, or better yet, use Zinzer Bullseye Primer Sealer.

Can Casein be used on dimensional materials?

Casein can be used effectively in collage and mixed media applications. It is also widely used for painting scenic and scale models. Casein's soft, natural finish gives miniatures a life-like appearance. Acrylic matte medium over the dry miniatures provides a final protective coating.


What kind of varnish should be used with Casein?

Varnish is a matter of preference. A gloss varnish will intensify the color. Using a matte acrylic varnish will preserve that 'authentic Casein' look.

What's the best way to apply varnish to Casein?

Spray varnish is the easiest method. Start the spraying process before the nozzle is over the area to be varnished and apply it in a diagonal direction over the painting, spraying in light, quick trails. Let it dry and repeat the process until you have the effect you want. When spraying varnish, follow appropriate safety procedures.

If you brush varnish over a painting with delicate glazes, some lifting may occur, especially if your brush is too coarse or if the paint has not fully cured. If you've painted relatively thick, brushing on varnish will work if applied carefully.

Does Casein Emulsion increase adhesion? Does it impact drying time?

Casein Emulsion increases adhesion and slows down the drying time.

Are Casein paints soluble with alcohol?

No, however, you can easily lift mistakes by using ammonia. Generally, a 1:9 ammonia: water mixture will be what is needed.


What kind of brushes should be used with Casein and how should they be cleaned?

You can use almost any kind of brush depending on the effect you want to create. Because it dries quickly, Casein can be hard on brushes, so make sure you clean them thoroughly with gentle soap and water or a commercial cleaner when your painting day is over.

Favorite brushes for casein: 

Can Casein be mixed and matched with other media?

You can use Casein directly with watercolor, gouache, and acrylics. With oils, use Casein for underpainting or apply it on top of an intermediary varnish.

Can Casein be used for impasto painting?

Casein paints are fine for a moderate impasto. To achieve a heavy impasto, it is recommended that you paint your impasto texture first, using thick gesso and a rough bristle brush. Then paint with Casein on top in the normal, liquid way.

If Casein is opaque, how can it be used for washes?

Casein is opaque, especially when white is added. However, when diluted with water, it can be applied in translucent layers, creating a gauze-like effect.

When Casein dries, the values can shift. What can I do about that?

Mix the color you want and apply a swatch on the area you want to paint. Use a hair dryer to dry the Casein quickly to check the color. After you have painted with Casein for a while, you will learn which colors lighten and darken by instinct. Remember, sometimes happy accidents "wake up" a painting!

Sometimes layers of Casein get muddy. Why is this happening?

Applying too many layers of color or not allowing them to dry thoroughly may mute or muddy colors. Speed up the drying time with a hair dryer.

What is Halftone Black?

Most Casein colors are opaque; halftone black is finely dispersed, allowing your underpainting to show through. When applied over another color, the color changes with incredible results. For instance, when you put halftone black over burnt sienna, you'll get a beautiful purple. Halftone black is also great for shading over flat areas of color.

Should white be added to Casein when using it as a wash?

Adding a touch of white to your Casein colors will help you control your washes. Five percent white will make washes lighten gradually from opaque to transparent instead of changing too rapidly.

Can Casein be used for fresco painting?

For fresco painting, Casein colors are thinned with water and applied to cement or lime walls, either wet or dry. The color should be of thin consistency.

Can Casein be used with resist-ink?

Some of the most exciting textural and tonal effects can be achieved using this technique. It involves nothing more than brushing waterproof black ink over a Casein painting. The greater the variety of surface textures, the more intriguing the results. Making sure the paint is completely dry, fill a soft brush with the ink and stroke it over the picture. It can be very black or diluted to different intensities. While it is drying, the ink will be absorbed into the areas with the thinnest coats of paint. The more thickly laid textures will repel it. When it has dried, run it under the faucet with cold water and allow the ink to wash off. It will leave a mottled half-tone effect.

What kind of water should be used with Casein?

Some people recommend distilled water, but ordinary tap water is fine.


How does Casein differ from watercolors?

While watercolors are transparent, Casein is essentially opaque. The main advantage of Casein over watercolor is that it's so easily correctable. It can be removed with a cloth, brush, or eraser, or if it's already dry, with a cloth dipped in ammonia and water (one part ammonia to nine parts water.)

...from acrylics?

The general characteristic/appearance of acrylic paint is a bright, bold color, stretching flatly across the canvas. Casein is often described as quiet and subtle, having a color depth similar to oils. While some acrylics can be used to produce a non-gloss finish, it is still different from the matte finish of Casein. Also, Casein can be used in mixed media techniques where acrylics cannot: as an underpainting for oil or mixed with watercolor.

...from gouache?

Gouache is similar to Casein in that it is an opaque medium that can be thinned with water and dries matte. Casein may be painted on a variety of rigid surfaces; gouache is best on paper. Casein has a height/volume to painted strokes that gouache does not have. Strokes tend to be more distinct and not as easily blended as gouache. Both mediums can be reworked, but casein will become harder to rework over time as the paint cures. The painting experience is also different: gouache feels more akin to watercolor painting; casein can feel more like oil or acrylic painting depending on the techniques used.

...from egg tempera?

The difference is mainly ease of use. Casein, which comes in tube form, is much easier to use than the complicated formula for egg tempera. Egg tempera also can only be worked on in small areas because of its quick drying time, while Casein brushes on more smoothly and dries much less quickly.


Does Casein have a shelf life?

Casein paint tubes may harden or separate a bit if they aren't handled frequently. Squeezing the tubes circulates the emulsion with the pigments, keeping them moist and pliable.

Can I refrigerate or freeze Casein?

For a short time (overnight), you can put them in the refrigerator to keep them fresh, but never put them in the freezer. Unlike other paints, Casein cannot withstand freezing temperatures, which will rupture the emulsion film, causing a breakdown in stability.