Casein: Making the Binder and Paint
Casein is a protein that comes from milk and can be made into a binder mixed with pigment to make paint. It can easily be made from milk, as I wrote in another article, but it's even easier to make it from dehydrated casein powder - just add water.
Rehydrating Casein Milk Powder:
At this point what we have is casein with no adhesive properties. To make it into a glue we have to add an alkai. Lime or ammonia hydrogen carbonate works well, but my choice is borax. This can be readily found in most laundry sections of a grocery store.
Rehydrating Casein Milk Powder:
- 2 tablespoons casein powder
- 5 tablespoons distilled water
- Glass jar @ 8 ounces
At this point what we have is casein with no adhesive properties. To make it into a glue we have to add an alkai. Lime or ammonia hydrogen carbonate works well, but my choice is borax. This can be readily found in most laundry sections of a grocery store.
Adding Borax to make Casein Glue:
(Caution: Borax should not be inhaled or get in your eyes.)
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.
Let it sit for @ 6-8 hours at room temperature for the hydrolysis process to be completed. It should look like the picture above where the casein has turned somewhat translucent.
It's now ready to use.
Yield is about 7 ounces of glue.
You can heat the jar in a double boiler bath or on a 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. You could add a drop of preservative, such as as Thymol, to prevent mold, but it's not required if you make a small amount.
(Caution: Borax should not be inhaled or get in your eyes.)
- 3 teaspoons borax
- 3 ounces hot distilled water
- Rehydrated casein solution from above
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.
Let it sit for @ 6-8 hours at room temperature for the hydrolysis process to be completed. It should look like the picture above where the casein has turned somewhat translucent.
It's now ready to use.
Yield is about 7 ounces of glue.
You can heat the jar in a double boiler bath or on a 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. You could add a drop of preservative, such as as Thymol, to prevent mold, but it's not required if you make a small amount.
Making Paint:
The picture above shows red oxide pigment (PR101) made into casein paint. On the top right corner of the paper are some test swatches I made, a thinned wash, a brush stroke, and a scraped stroke made with a paint knife. Below this is a sample of the commercial casein paint from Shiva (now Richeson) of the same pigment color.
Prepare the 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.
Make a small dent in the pile and pour in @ 1 teaspoon water.
Fold the pigment into the water. A long flat palette knife works well.
Add drops of water as necessary and mix it up until you get a thin paste that doesn't cake and is not too wet.
Some pigments are hydrophobic (repel water,) so it's helpful to add a few drops of ox gall or grain alcohol to help them mix better when wet.
Add Binder to Paint:
Thin about 1 tablespoon of the casein glue with about 5 times more water. This will be your binder.
Add small amounts of this to the pigment paste. Do not add the paste to the binder, 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 binder is generally needed.
Test your paint on spare sheet of 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, or add fillers like whiting or chalk to bulk it up, if you prefer. Fillers can affect the color properties of the paint, so use sparingly.
Notes:
Casein powder can be found at various art material suppliers that sell raw pigment, such as:
Kama Pigments
Sinopia
Natural Pigments
I've seen health stores that offer raw casein powder as a protein drink additive. I've not tested it out, but it might be a good supply source. Make sure it is just casein with no flavorings added.
An advantage to making it from powder as opposed to using raw milk is that there is less waste product. You're just paying for the casein, and not all the excess liquid. A pound size bag has lasted me several years since a little goes a long way.
In place of borax, ammonia hydrogen carbonate powder can also be used (aka: hartshorn, or smelling salts.) 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, which is not a concern for borax or ammonia. 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 won't be necessary.
The dry casein powder has an unlimited shelf life, but will likely lose its adhesive properties after a few years when made into a binder. The rehydrated casein will not likely last longer than a few weeks in refrigeration, but in glue form has lasted me up to 4-6 months in refrigeration. I can also add a drop of preservative, such as Thymol, to keep it longer out of refrigeration. Typically, I make only about 6-8 ounces at a time, or more if I'm planning to also 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 would water alone. Honey is another option. Diluted glycerin will work as a plasticizer (flexibility) 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.
Casein binder can be mixed with oil as an emulsifier. You can mix it with oil mediums, or also add in dry pigment to make a nice thin oil paint that can be thinned with water. This works well as an underpainting oil medium.
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.
Prepare the 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
Make a small dent in the pile and pour in @ 1 teaspoon water.
Fold the pigment into the water. A long flat palette knife works well.
Add drops of water as necessary and mix it up until you get a thin paste that doesn't cake and is not too wet.
Some pigments are hydrophobic (repel water,) so it's helpful to add a few drops of ox gall or grain alcohol to help them mix better when wet.
Add Binder to Paint:
Thin about 1 tablespoon of the casein glue with about 5 times more water. This will be your binder.
Add small amounts of this to the pigment paste. Do not add the paste to the binder, 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 binder is generally needed.
Test your paint on spare sheet of 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, or add fillers like whiting or chalk to bulk it up, if you prefer. Fillers can affect the color properties of the paint, so use sparingly.
Notes:
Casein powder can be found at various art material suppliers that sell raw pigment, such as:
Kama Pigments
Sinopia
Natural Pigments
I've seen health stores that offer raw casein powder as a protein drink additive. I've not tested it out, but it might be a good supply source. Make sure it is just casein with no flavorings added.
An advantage to making it from powder as opposed to using raw milk is that there is less waste product. You're just paying for the casein, and not all the excess liquid. A pound size bag has lasted me several years since a little goes a long way.
In place of borax, ammonia hydrogen carbonate powder can also be used (aka: hartshorn, or smelling salts.) 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, which is not a concern for borax or ammonia. 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 won't be necessary.
The dry casein powder has an unlimited shelf life, but will likely lose its adhesive properties after a few years when made into a binder. The rehydrated casein will not likely last longer than a few weeks in refrigeration, but in glue form has lasted me up to 4-6 months in refrigeration. I can also add a drop of preservative, such as Thymol, to keep it longer out of refrigeration. Typically, I make only about 6-8 ounces at a time, or more if I'm planning to also 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 would water alone. Honey is another option. Diluted glycerin will work as a plasticizer (flexibility) 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.
Casein binder can be mixed with oil as an emulsifier. You can mix it with oil mediums, or also add in dry pigment to make a nice thin oil paint that can be thinned with water. This works well as an underpainting oil medium.
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.