Casein is paint made from milk protein, used since ancient Egypt. Learn how Klimt, Warhol, and Native American artists used a fast-drying medium that dries hard and matte.
In 1801, a French scientist named Antoine-Alexis Cadet-de-Vaux presented a paper to the French Academy of Sciences about a paint made from milk. The country was in the aftermath of the Revolution, oil and linseed were scarce and expensive, and people needed a way to paint their houses and furniture at a fraction of the cost. Cadet-de-Vaux's recipe, made from soured milk curd mixed with lime and pigment, produced a durable, matte paint that could withstand rubbing and weather better than traditional distemper. He was so confident in the result that he had his own library ceiling and floor painted with it. The painter he hired initially dismissed the mixture as a "botched batch" but changed his mind when he saw the ceiling dry in hours and resist the scrub of a coarse cloth. Cadet-de-Vaux's "memoir on painting in milk" is one of the earliest documented recipes for casein paint, but the medium itself is far older. Milk-based paint has been found on a stone tool in a South African cave dated to 49,000 years ago.
Casein is a paint made from casein, the primary protein in milk, used as a binder for pigment. The casein is precipitated from milk by adding an acid or the enzyme rennet, then dissolved in an alkaline solution, typically lime, borax, or ammonium carbonate, to create a liquid binder. When mixed with pigment and applied, the casein forms a hard, water-resistant film as it dries through protein coagulation and the reaction with the alkali. The resulting paint dries quickly, adheres well to porous surfaces, and produces a matte finish that can resemble oil painting more than other water-based paints.
This entry covers how casein paint works, its long history from ancient Egypt to 20th-century illustration, the artists who used it, and why it was displaced by acrylic paint in the 1960s.
Casein paint starts with milk. The casein protein, which makes up about 80% of the protein in cow's milk, is separated from the whey by adding an acid (like vinegar or lemon juice) or the enzyme rennet. The resulting curds are then dried and ground into a powder. To make paint, the casein powder is dissolved in an alkaline solution. Lime (calcium hydroxide) is the traditional alkali, producing a paint that works best on porous surfaces like wood or plaster. Borax casein, developed later, is pH-neutral and has a longer shelf life. When a small linseed oil is added to borax casein, the paint can last for months.
The drying mechanism is similar to egg tempera. The casein proteins coagulate as the water evaporates and the pH changes, forming a hard, insoluble film. Unlike egg tempera, which remains somewhat flexible, casein dries to a rigid, brittle film. This makes casein unsuitable for flexible supports like stretched canvas, where the paint would crack as the canvas expands and contracts. Casein works best on rigid supports like wood panels, masonite, or illustration board.
Casein paint has several properties that made it valuable to artists. It dries quickly, like tempera, but can be reworked for a period before the binder fully hardens. It dries to an even, matte consistency, which makes it ideal for murals and large flat areas. It can visually resemble oil painting more than other water-based paints, because the casein film has a density and opacity that watercolor and gouache lack. And once fully hardened, casein paint is water-resistant and chemically stable, which is why it was used for outdoor applications and murals long before acrylic existed.
A 2025 study in Analytical Methods compared the physicochemical stability of proteinaceous binders, including casein, egg white, and egg yolk, in traditional painted coatings. The research found that casein markedly increases specular reflection (gloss up to approximately 39 GU) but induces measurable darkening and desaturation of color, while egg white preserves chromatic stability. The study also showed that the malachite green-casein system retains higher residual mass and superior thermal stability compared to egg-derived binders. Read the study at RSC Publishing.
The use of milk as a paint binder is ancient. Goat's milk provided the binder for lacquer paint used on the tomb of King Tutankhamun in ancient Egypt. The 49,000-year-old stone tool from South Africa, coated with a mixture of wild bovid milk and ochre, represents the earliest known use of milk as a paint binder, tens of thousands of years before the domestication of cattle. Throughout the medieval and early modern periods, casein was used as a form of distemper paint for interior decoration and furniture.
Casein paint did not become a recognized fine art medium until the late 19th century. William Morris Hunt's Niagara (1879) is one of the earliest known paintings made with casein paints by a recognized artist. Hunt, who typically worked in oils, applied casein to a prepared canvas support, demonstrating that the medium could produce results comparable to oil for certain subjects.
Gustav Klimt used casein for his Beethoven Frieze (1902, Secession Building, Vienna), a 24-meter wall painting created for the fourteenth exhibition of the Vienna Secession. Klimt applied casein paint directly onto mortar with added stucco, gold leaf, and other materials. The choice of casein for a wall painting was deliberate. Casein is more accommodating than fresco, does not require the rapid execution that wet plaster demands, and produces a surface that is durable and matte. The Beethoven Frieze survives today as one of the most significant casein paintings in art history.
In the 20th century, casein found its greatest use among commercial illustrators. Before the invention of acrylic, most house paint that was not oil-based used casein as a binder. Casein was the material of choice for illustration work because it dried fast, covered well, and could be reworked. Artists like John Berkey used casein in combination with acrylics for his science fiction and western illustrations. Andy Warhol, who worked as a commercial illustrator before becoming a fine artist, used casein for early paintings like Dick Tracy (1960) and Popeye (1960).
Native American artists also adopted casein extensively. Oscar Howe (Yanktonai Dakota) used casein for his paintings that combined Native American themes with modernist abstraction. Pablita Velarde (Santa Clara Pueblo) created a series of more than 70 paintings of everyday Native American life in New Mexico for Bandelier National Monument between 1937 and 1943, painted mostly on masonite using casein paints.
Klimt's Beethoven Frieze (1902, Secession Building, Vienna) is the most significant casein painting in art history. The 24-meter frieze, depicting the human desire for happiness through a narrative inspired by Beethoven's Ninth Symphony, uses casein paint applied directly onto mortar with stucco, gold leaf, and other materials. The casein medium allowed Klimt to work on a wall surface with more flexibility than fresco would permit, and the matte finish of the casein provides a subtle ground against which the gold leaf sections glow by contrast.
Warhol's Dick Tracy (1960) and Popeye (1960), both in the Museum of Modern Art's collection, were painted with casein. These works date from the period when Warhol was transitioning from commercial illustration to fine art, and the choice of casein reflects his background in commercial art, where the medium was standard. The flat, graphic quality of casein suited the comic-book imagery that Warhol was beginning to explore.
Howe, a Yanktonai Dakota artist from South Dakota, used casein for paintings that challenged the expectations placed on Native American artists. Works like Umine Wacipe (War Dance) (1958, Smithsonian National Museum of the American Indian) use casein's matte, opaque quality to create dynamic, abstracted compositions that draw on Dakota visual traditions while engaging with mid-century modernism. Howe's use of casein was part of a broader movement of Native American painters who adopted the medium for its durability and matte finish.
Velarde's series of paintings for Bandelier National Monument (1937-1943), created mostly on masonite with casein paints, document everyday Native American life in New Mexico. The paintings, now in the collection of the National Park Service, demonstrate casein's suitability for detailed, narrative work on rigid supports. Velarde ground her own pigments and prepared her own casein paint, following traditional methods.
Hunt's Niagara (1879) is one of the earliest known casein paintings by a recognized American artist. Hunt typically worked in oils, and his decision to use casein for this landscape may have been experimental. The painting demonstrates that casein could produce effects comparable to oil for landscape subjects, with a matte finish that suited the atmospheric quality of the falls.
Casein occupies a distinct position among water-based paints. Unlike watercolor, it is opaque and dries to a hard, matte surface. Unlike gouache, which remains water-soluble and can be reactivated indefinitely, casein becomes water-resistant once fully hardened. Unlike egg tempera, which uses egg yolk as a binder, casein uses milk protein and dries to a harder, more rigid film. And unlike acrylic, which is a synthetic polymer, casein is an organic material that has been used for millennia.
The main disadvantage of casein is its short shelf life. Lime-based casein must be used fresh, within hours of mixing. Borax casein lasts longer but still has a limited working time compared to acrylic, which can sit on a palette for days. The brittleness of the dried film also limits casein to rigid supports. These practical constraints are why acrylic, introduced in the 1950s, largely replaced casein in both fine art and commercial illustration by the late 1960s.
Despite this, casein paint is still manufactured and used. Pelikan produces casein paint under the brand name Plaka, and some artists prefer it for its specific handling qualities: the matte finish, the opacity, the ability to resemble oil paint, and the historical continuity with centuries of painting practice.
Casein paintings are not always labeled as such in museum displays, which can make them difficult to identify. Klimt's Beethoven Frieze at the Secession Building in Vienna is the most accessible major casein work. The Bandelier National Monument in New Mexico displays reproductions of Velarde's casein paintings, with the originals held by the National Park Service. Warhol's early casein paintings are at the Museum of Modern Art in New York.
When you see these works, notice the surface. Casein has a matte, even quality that is different from both oil and acrylic. It is flatter than oil, less plastic than acrylic, and harder than gouache. It looks like what it is: paint made from milk, dried to stone. For more on related protein-bound and water-based mediums, read our entries on tempera, gouache, and acrylic painting, or explore our blog post on how to read a painting.
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