This is a tutorial on how to prepare the grinding tools and disperse pigments into water to make your own water-based paint. This technique can be used to prepare dispersions of pigment in water to be mixed with gum arabic solution for watercolors, egg yolk for egg tempera, casein solution for casein paint, animal glue for distemper and for use in fresco painting. The same technique can be used to disperse pigments in preparation to make pastels and pigment sticks.

Why grind pigments to make your own paint? There are two basic reasons for doing so: To break down agglomerates of pigment particles and to evenly disperse pigments in the paint binder. Most artists are aware of the need to smoothly mix pigment with a binding medium, but few are aware of how breaking agglomerations of pigment particles can also improve the color saturation of the paint. Fewer still know about the possibilities that grinding pigments afford for altering the visual appearance of paint.

Dispersing pigments into a paint binder with a muller on a flat surface helps to breakdown agglomerations or pigment particles that clump together from moisture and other weak binding forces. This helps to not only make the final paint smoother, but improves the opacity and color saturation of the paint. However, it is a common mistake to think that the force of grinding with a muller on a flat surface actually grinds pigment particles into smaller sizes. Greater mechanical force must be applied in order to do so. One way to do this is with a mortar and pestle. A pestle directs the entire force to a single point whereas a muller applies the same force spread out on its flat bottom surface. In addition, the pressure applied to the concave surface inside a mortar creates greater lateral forces to shear the particles in smaller ones. The action of grinding in a mortar can reduce the particle size of the pigment and, in some cases, alter its color substantially.

Comparison of pigment particle sizes of malachite

Not all pigments improve in color and appearance by being ground to a very fine powder and then mixed with a binding medium. For example, the natural mineral malachite loses its color saturation the finer it is ground. On the other hand, some pigments, like cinnabar and lazurite (lapis lazuli) improve their chromacity when grinding to the finest possible particle sizes.[1]

Many synthetic pigments available to artists today are already prepared in extremely fine grades, since they are essentially made from precipitated chemical compounds. Whereas this makes for very uniform and small pigment particles that offer some advantages in covering power and tinting strength, it also removes the interesting textures and intense chromacity found in natural pigments. At the very least, it does not allow the artist to control the pigment to its best potential in painting. Grinding pigments gives you the tools to overcome this limitation.

Rublev Colours pigments from Natural Pigments are made to careful specifications that do not destroy the pigments best qualities and also allow the artist to refine them for his or her own use through elutriation or grinding. Many Rublev Colours pigments are basically raw materials that may require further processing by the artist to achieve certain desirable effects. Rublev Colours pigments can be used as they come out of the jar or you may grind them to smaller particle sizes and separate into different grades for special visual effects. As you become more aware of these possibilities, you may want to experiment, paying close attention to the way the pigments look when mixed with your medium, whether it is oil, egg, acrylic, casein or gum arabic.

Tools Needed to Make Your Own Paint

The tools you need to disperse pigments and make paint are quite simple and most are available locally. For convenience, Natural Pigments has put together a Basic Paint Making Kit to help you get all the tools and materials you need to get started. Here are the tools you will need to get started:

Item Where To Find
muller Muller Glass, stone or ceramic muller
Glass muller large, small and medium sizes are available
Included in the Basic Paint Making Kit
grinding surface Grinding surface Plate glass at least quarter-inch thick, marble, granite or other smooth, non-porous flat surface.
Grinding Plate (10 x 10 Inches)
Included in the Basic Paint Making Kit
spatula Spatula, palette or putty knife Spatula
Included in the Basic Paint Making Kit
Also available from hardware stores and art supplies stores
silicon carbide Silicon carbide Also known by its tradename, Carborundum. Use 100 or 200 grit to prepare the surface.
Silicon Carbide (100 grit) 100g
Included in the Basic Paint Making Kit
  Water Distilled water is preferred
Supermarket or food stores
gloves Gloves Latex, nitrile or polyethylene gloves
Available from pharmacies, drug stores and medical supply stores
dust mask Dust mask NIOSH-approved dust mask or respirator
Available from hardware stores
safety glasses Eye protection Safety glasses or goggles
Available from hardware stores
wide mouth jars Jars Wide Mouth Jar 4 oz

CAUTION: Always wear a NIOSH-approved dust mask while grinding or working with any dry earth or pigment. Wear protective clothing and gloves while working with pigments in any form—dry or wet.

Preparing the Grinding Surface

The grinding surface must be roughened before it is useable for dispersing pigments. You will need about 15–20 minutes to prepare the surface for dispersing pigments. Here are the steps you should follow to prepare the surface:

Step 1: Place the surface on a firm support such as a countertop or firm table. If you are using glass as your grinding surface, you may find it helpful to put a white washcloth or a white kitchen towel beneath the glass to stabilize it while grinding.

preparing the grinding surface

Step 2: Pour a small amount of silicon carbide onto the surface. About 1/8 of a teaspoon will be fine to start with. Apply distilled water to the silicon carbide a drop at a time to make a stiff paste.

Step 3: Mix the water into the silicon carbide to make a paste the consistency of toothpaste.

prepare silicon carbide paste

Step 4: Place the muller onto the small pile of silicon carbide paste and begin moving it a circular motion reaching to the edges of the surface. The corners of the grinding surface do not need to be roughened. Continue to grind in this motion for 5 to 10 minutes.

scraping the paste

It will be necessary to remove accumulated silicon carbide paste from the sides of the muller using a scraper, palette or putty knife. Periodically scrape the paste into a small heap at the center of the grinding surface in order to continue grinding. When you have completed grinding the surface, visually inspect it to see if it has been roughened by holding it up to a light at an angle. If the surface was smooth and shiny to begin with, you should notice a matte appearance where you have been grinding.

To avoid contaminating your pigments, clean your tools well by washing with soap and water.

Dispersing Pigment into Water for Water-Based Paint

Now that the grinding surface has been prepared, you can begin to dispersing pigments and making your own paint. Lets disperse some pigment intended for use with water-based mediums, such as egg yolk (tempera), animal glue (distemper), gum arabic (watercolors) or fresco. It is best to disperse the pigment in distilled water. Tap water may contain a high amount of minerals and perhaps bacteria that may contaminate your paint.

Step 1: Place a small amount of pigment in a heap at the center of the prepared surface. Start by working with about 10 grams of pigments.

add water to pigment pile

Step 2: Add a small amount of distilled water to the heap of dry pigment a few drops at a time. Do not add too much water to start.

mix water with pigment powder

Step 3: Mix the water into the pigment with a spatula, palette or putty knife. The correct amount of water is added when the pigment has the consistency of toothpaste. It is easier to judge the thickness of the paste once you begin grinding with the muller. Hence, in the beginning it is better to begin grinding with a stiff paste than one that has excess water.

mulling or grinding pigment paste

Step 4: Holding the muller firmly with the heel of your hand down and your thumb up, slowly move the muller in a circular motion while keeping the pigment in the center of the surface. The pigment will slowly accumulate along the outside of the circle. Use the spatula to move the paste to the center of the grinding surface in order to continue grinding.

If the paste becomes too stiff, add more water a few drops at a time. Do not worry if suddenly the pigment is thin and watery. Simply add more dry pigment to the mixture.

scrape pigment from muller

Periodically lift the muller from the grinding slab and remove any accumulated pigment from the sides of the muller using a spatula, putty or palette knife.

Sometimes suction will form between the muller and grinding surface making it difficult to move or lift the muller. Use the spatula as a lever to raise an edge of the muller. Then slide the muller horizontally off the grinding surface.

To prevent contaminating your next pigment, clean your tools very well. If you have been grinding with water-based media, wash with warm water and soap. If you are grinding with oil, clean up with odorless mineral spirits or d-limonene solvent. Always wash your grinding tools with warm water and soap after cleaning with solvents. You may remove caked-on pigment and paint by grinding with any kitchen scouring powder, borax or silicon carbide with the muller on the grinding surface. Follow this by washing with soap and warm water.


References

Thompson, Daniel V. The Materials and Techniques of Medieval Painting. Dover Publications, Inc., New York, 1956, ISBN 0-486-20327-1, p. 86.