D B Clemons - Making Casein

Stage 1 - Rehydrating Casein Milk Powder:
2 tablespoons casein powder
5 tablespoons distilled water
Glass jar @ 8 ounces

Place the powder in the jar and add the water. Stir and cover container, and let sit overnight in refrigeration (@ 8-12 hours.) It will have a consistency like yogurt or custard. A thinner mix (1:5) will be fine for painting, but this mixture works best for gesso, and can be later diluted as a painting medium.

Stage 2 - Adding Borax:
(Caution: Borax should not be inhaled or get in your eyes.)
3 teaspoons borax
3 ounces hot distilled water
Casein solution from Stage 1 above

Heat the water (not to boiling - just hot to touch @ 140° F,) and stir in the borax briefly until dissolved.
Stir up the casein solution for any curds that may have settled at the bottom of the jar.
Add the borax solution to the casein slowly while stirring until it reaches your desired consistency.
Let it sit for @ 4 hours at room temperature for the hydrolysis process to be completed.
It's now ready to use.

Yields about 7 ounces of glue.

You can heat the jar in a double boiler bath or coffee cup warmer to make it less viscous if desired. Heating is not required, however. Room temperature is fine.

The water amount can vary. A very diluted emulsion will make a paint that's more like watercolor or ink. A thicker type makes a good glue, but it may be unmanageable for painting.

Keep it refrigerated when not in use, and warm it to room temperature before using. This glue will last from 4 to 6 months. Although it doesn't spoil in 6 months time if refrigerated, it becomes too thin and watery, losing adhesion, and should be discarded.

Stage 3 - Wetting Pigment to Make Paint:
Caution: pigments can be hazardous, so handle them with appropriate care. Don't work or clean up in an area where food is prepared.

1 ounce dry pigment
Ready supply of distilled water

Place pigment powder in a pile on your work area.
Make a small dent in the pile and pour in @ 1 teaspoon water.
Fold pigment into water. A long flat palette knife works well.
Add drops of water and mix it up until you get a thin paste that doesn't cake and is not too wet.

Stage 4 - Add Binder to Paint:
Add small amounts of the glue to the pigment paste. Do not add the paste to the glue, since it mixes better adding wet to dry. Add about 1 teaspoon of binder at a time, depending on how much pigment you wetted, and mix it together thoroughly.

Mix until you reach the desired opacity and viscosity. That property is up to you. The amount you must add will also vary by the type of pigment you're mixing, since some require more, some less. Look at the labels on tubes of paints you buy for clues to their pigment transparency or opacity level. Very little emulsion is generally needed.

Test on spare paper for proper adhesion. If it's too weak (rubs off easily when dry) add more emulsion.
If the paint gets too liquid, you can thicken it by adding it to more pigment paste, or add fillers like whiting or chalk to bulk it up, if you prefer. Fillers can affect the color properties of the paint.

Other Notes:
The casein powder can be found at various art material suppliers that sell raw pigment, such as:
Kama Pigments
Pigments Plus in NYC
Sinopia
Natural Pigments

Pigments Plus lists casein paint in their catalogue, but I've not tried them yet. They're the only other commercial suppliers of paint I've seen other than Richeson's Shiva brand.

Casein can be made directly from skim milk, of course, and the process is faster since you don't have to rehydrate the powder, but you should avoid using any fortified milk product that has additives, which is not easy to find.

There's a type of casein paint referred to as "milk paint" sold for painting furniture. These often also contain other things like asbestos, clay, or lime in powder form, so be certain of what you're getting if you're trying out different sources.

Why use borax? A caustic agent is required to make the casein protein soluble in water, and turn it into glue. There's a type sold in grocery stores as laundry soap "booster," and it works fine. Different types of borax have degrees of hydration, as I understand it, but they all dissolve quickly with no residue.

In place of borax, ammonia hydrogen carbonate can also be used (aka: hartshorn.) Ammonia is strong and thins the glue more, plus it has an odor you need to contend with. Slaked lime will also work, and this is a historic fresco medium, but it's only safe to use it with pigments that are alkali fast. Lime also takes longer for the hydrolysis effect to occur, @12 hours. There's another product called tri-sodium phosphate (TSP) that will also work, but it's more expensive by volume than borax, and is banned in some states because of the phosphate content.

Raw pigment can sometimes be rough and gritty, so invest in a glass muller for further grinding. For most pigments, that's not necessary.

The dry casein powder has an unlimited shelf life, but should be kept in a cool dry location. The rehydrated casein will not likely last longer than a few weeks in refrigeration, but the binder has lasted me up to 4-6 months. I typically make only about 6 ounces at a time, or more if I'm planning to make gesso.

Diluted corn syrup can be added in small amounts to increase flow and slow the drying of the paint without severely thinning it as with water alone. Honey is another option. Diluted glycerin will work as a plasticizer and also slow the drying time. I almost never add anything extra for painting, even water, unless I need a wash affect or for underpainting. Most often I just add more emulsion to the paint as needed for glazing.

A thin spray of clear de-waxed shellac will isolate layers of paint to prevent lifting by a new wet layer. I use it if I'm doing a colored underpainting. Workable fixative also does this, but these materials can discolor the pigments so use with care. The best method is to just use a light touch with a soft brush and full-bodied paint.