Casein paint has been used by the
ancients on wood panel paintings, wall murals and has also used
successfully as a household/architectural paint. When applied properly
on the right support it has proven itself to be an archive quality
paint. The glue was developed by old
master craftsmen for making furniture and musical instruments, the binder
is actually a fast-drying
water soluble glue produced from milk
proteins. White glue still used today by some cabinet makers is made from casein. At the
factory the casein is dried and ground up before it is made into
glue. Since as a painting medium (binder) it is
only water soluble
until dry, it has also been successfully used in conjunction with other mediums
such as watercolor and egg tempera.
Casein for sealing or building grounds
Many conservation authorities believe that casein
is inferior to RSG as a sizing material or binder for grounds
because of its tendency to become brittle with age but, casein glue
posses superior archival qualities compared to animal glues for adhesion,
sealing and moisture resistance when used on the proper support.
Casein is in fact a water soluble material but after time cures into
a hard insoluble non absorbent film.
The purpose of a size is to isolate the ground from
and reduce the rate of absorption of a medium into the support.
casein performs this task exceptionally well. Due to it's brittle
properties though, it is more appropriately used for sizing rigid or cradled wood
panels or fiberboard where it also becomes an excellent choice for preparing
panels covered with canvas or paper for just about any medium. Use
of casein is also less difficult to use for sizing than RSG because it is less temperature sensitive
once a batch is made and does not require heating to apply.
Another favorable use for casein as a ground is
with silver point drawings where it provides more tooth than acrylic
gessoes and chemically reacts with the metals to accelerate the
patina. Some modern silverpoint grounds are made with a blend of
casein glue and calcined bone and/or zinc white casein paint.
However, any color pigment could be added to create a toned canvas to
Casein definitively has a matte
finish that egg tempera readily bonds to. This
practice in turn can also be used to seal panels for oil paintings
where it is not uncommon to first layer the under paintings with the
faster drying egg tempera.
Since there have been several commercial
fixatives marketed consisting of hazardous diluted varnish and
shellac resin solutions in solvents like alcohol or benzene, there
has been rightful concern among artist in regards to the health
hazards from their use.
"Flatiron Building" 40"
Colin Campbell Cooper - 1908
Casein on canvas
There is supporting documentation verifying
that artists such as Degas and Cassatt used casein glue diluted with
alcohol and water as a fixative for pastel paintings. Artist
Della Heywood manufactures and markets a non-hazardous
dry media intermediate (workable) and final
casein spray fixative
sold as "SpectraFix
" that works great with charcoal, pastel, conte crayon and pencil
drawings. You can also make your own (see below).
Making your own Casein Sizing and Paint
Casein Paints can be purchased in tubes
it is also sold as a light yellowish
powder from where the glue is made by adding distilled water to the
dried material, allowing it to absorb the water and neutralizing with an alkaline substance such as
aqua ammonia or ammonium carbonate. You can find some of those
recipes provided by Kremer Pigmente here.
However, there is debate as to
whether it is any better or easier to make it fresh. I favor the
later. Much like egg tempera the best results from Casein are
achieved by blending the freshly made medium with Dry
but it will also blend well with higher quality tube watercolors if
The only drawback is, this glue can have a relatively
short shelf life where once it starts souring you should throw it away.
This means that when making your own casein medium you should make
small batches as you need it and to avoid waste and never grind large quantities
of medium with pigment unless you intend to use it.
Refrigeration helps to preserve the medium when storing your
medium in an air-tight container that has been sanitized with
- 1 Enameled or Pyrex pot (non-metallic)
- 1 qt
- 6 oz
- 4 oz distilled
water (tap water is susceptible to bacteria mold growth)
- 1 oz borax (can be substituted with
baking soda, quick lime, aqua
ammonia or ammonium carbonate)
It is important to start with a non fat milk also
known as 0% fat milk which will not contain the of contamination of
unwanted butterfat and other nondrying fatty oils. To
assure good separation, the milk should be warmed but do not heat
higher than 110° F to prevent destroying the
properties of the casein. Extracting casein in a cold solution is
also a cause for the inferior
formation of casein. This must be done in an enameled or Pyrex pot
since some metals such as cast iron, aluminum and copper will react
with acidic materials resulting in contamination.
In making your casein glue you intentionally alter
the milk's already low pH chemically by slowly adding acidic acid
(white vinegar) while stirring to turn it sour. When the milk
is placed in an acidic state you initiate the
precipitation of the gelatinous lumpy consistency (casein proteins) from
left which is mostly water. Note: This is the sensitive part of
the procedure. By adding acid too quickly or the accumulation of too
much acid in the solution will dissolve some of the casein. You only
need to add enough acid to acquire good separation of the curd and
Casein is amphoteric, meaning that it will produce salts with both
acid and alkaline states. A higher
acidity will produce undesired excess salts once
the casein has been neutralized. Therefore
it is important not to fluctuate anymore than needed within
the pH scale.
Continue to warm and stir the milk until the lumps (curds)
begin to develop and
then take off heat allow to settle. The
remaining yellow liquid (whey) is discarded by filtering through
doubled cheese cloth or linen.
Wash the casein by blending the casein curds with
the addition of clean distilled water and stirring lightly. Allow
the casein to separate and drain off the water through a filter. To
clean out any remaining fatty oil contaminates, to sterilize the curds,
and assist drying wash the filtered curd with isopropyl or
grain alcohol. Sterilizing from contaminating bacteria will make your paint medium keep longer.
Return the casein curd to a clean glass container after laying out
on a cotton cloth to allow any excess moisture to dry.
The solid curds are then neutralized with a aquatic
alkaline substance where in solution a strong adhesive is made. By the addition of baking soda, borax, quick lime, aqua ammonia,
ammonium carbonate, etc., or any alkali substance the casein curds
will become water soluble until it dries.
Note: Personal protection precautions must be taken to avoid
contact with alkaline substances (especially the eyes).
Aqua ammonia or ammonium carbonate are most
commonly used in casein production but due to their evaporative nature they are also susceptible
to a drifting unstable pH. Using aqua ammonia in your studio would also
require sufficient ventilation to remove gaseous
ammonia and carbon dioxide fumes.
Borax is the most commonly used where it raises
the pH higher and buffers the medium from drifting acid making it an
excellent casein pigment binder. When Borax is used your medium will
also keep longer when refrigerated as long as your storage
containers have been sanitized with alcohol before using.
Neutralizing with Borax
Dissolve borax in hot (not boiling) distilled
water and add the solution to the casein curd while stirring
until it develops a paint consistency. Because this hydrolysis
process is slow you should allow to sit 4-6 hrs to be certain the
reaction has finished. This is your Casein medium.
Hydrolyzed lime casein
Hydrating with (slaked) lime or Fresco Lime Putty makes a durable casein binder.
However, due to it's insolubility and high pH it is best to dilute to a
thin paint consistency before hydrolyzing. Caution must be taken to
prevent adding too much alkali material since high alkali substances
can also effect some pigments. This is especially critical if using
calcium hydroxide (quick
lime). However, this can be easily remedied by
making gradual lime additions and testing to achieve a neutral pH of 7.0 - 8.5 with an
inexpensive soil pH meter or by using mineral Pigments
used specifically for frescoes. Since lime is a strong corrosive
alkali, be sure to check MSDS
for hazard precautions.
Premix your lime in a large plastic or glass container slowly
adding distilled water to wet all of the lime into a paste. Continue this
dilution slowly until mixed to a thin paint consistency. If using
slacked lime putty for this instead of lime powder, dilute to the
same consistency. Initially blend 8 - 16 oz of this milky mixture of water and
slacked lime by adding in small quantities at a time and while monitoring the pH.
Add the lime paste to the casein curds while stirring. The lumpy
curds should immediately start breaking down from the alkalinity of
the lime. If it appears lumpy allow it stand while the reaction
takes place and
then return to stirring until it breaks down into a smooth paint.
Allow sufficient time to be certain the
reaction is complete. Add additional distilled water in minute amounts as needed and strain through
cheesecloth. This can now be used as your medium.
The above viscous solutions (either neutralized or
hydrolyzed casein) are thinned with
distilled water to a thinned paint consistency. Two coats will seal
well enough to proceed.
Borax neutralized Casein:
- 1 part titanium or zinc white
- 3 parts calcium carbonate (caulk)
- A few drops of alcohol to facilitate mixing
into a paste
Once your pigment and caulk is ground to a smooth a creamy consistency,
in a clean container blend with your sizing in
equal parts of size and pigment paste until it's a smooth and creamy
opaque white. At this time it should be strained again through cheese
cloth and can be thinned to use like paint .
Hydrolyzed lime casein:
Addition of titanium white
pigment first ground into a paste with alcohol and blended in equal parts with
casein medium will
make a sufficient gesso ground. The addition of caulk filler is not
needed since the lime and pigment will provide adequate opaque
coverage. After a few coats this dries to become an absorbent plaster
Making the paint
Grind dry pigment with a small quantity of
distilled water into a wet paste. With difficult pigments such as
titanium white add a few drops of alcohol to break down the
pigment. Then add casein medium to desired viscosity. Additional water can
be added at this time for thinning.
mind that a small amount of pigment goes a long way and that all
(especially dry) pigments must be treated as harmful substances. The
is a good resource for hazardous
pigment listings and handling tips. Use
safety precautions to avoid contact with skin, always wear an
industrial vapor face mask and work in well ventilated areas
to avoid breathing dust. Do not eat or drink in the same room as
pigments and wash your hands frequently.
"Solomon's Temple, Colorado"
26" casein on canvas
Colman Jr. - 1888
Used as a painting medium
used with casein are much like that of Egg Tempera
Painting or maybe even more like a lighter version of
Acrylic and it dries uniformity into an opaque mat finish
that works well for use as an under painting. Casein can be thinned
working very well as a transparent wash or glazing. However, the medium
does not flow as well as most water based mediums because it dries
fast. Where fine details can be painted easily it responds best to
daubs and short stokes. Caution must also be taken to avoid heavy
layers as not to build up stroke texture (unless it is your intention) since this is a heavy bodied
If the paint has not dried long, errors can be
corrected where it can be removed with a damp rag, fine grade
sandpaper or a hard eraser. Because dried casein is insoluble in water but is soluble in alkaline solutions, for more
difficult areas you can remove the paint
gently with a 10% aqua ammonia solution on a rag.
Note: Unless you can afford to throw away your
brushes you must wash them immediately after use. You can usually
get all of the paint out with soap and water but, if you have any stubborn
medium it can be dissolved in 10% aqua ammonia solution
and rinsed with water. Do not allow brushes to set in water. If the
binder has had the opportunity to set it is difficult to remove.
Casein as a Fixative
Casein also works well as both a workable and
final fixative for all dry pigmented media. It dries clear with
a matt finish that won't alter pigment hues on canvas and does
not interfere with the tooth of your canvas (a plus for layering
pigment). Although you can purchase it ready made, it is not a
complicated process to make your own.
The fixative is merely a mixture of:
- 1 part / 2 oz. - casein glue medium (neutralized
with Ammonia or Borax)
- 2 parts / 4 oz. - grain alcohol or water white
spirits such as gin, vodka, etc.
- 5 parts / 10 oz. - distilled
Blend thoroughly to make a thinned mixture.
If solution is cloudy allow it to stand for a brief period to
look for settlement at the bottom where the clearer liquid can be
removed from the top. The fixative should then be filtered either
through a coffee filter or wet cheesecloth and a funnel where it can
be put in a good quality pump spray bottle or air brush. If using an
air brush, use in small quantities and flush out well with an aqua ammonia
solution after use.
Images on this page provided by The
Casein Recipes - (from casein powder)
Pigments Co.- Recipes
for Artist's Casein
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