Kids, what do you think makes the vivid color of paints stay bright for years and years? Unlike paints made from plants or other sources, paints made from minerals hold their color well over time. But they can be hard to make when the minerals are rock-hard. Soft minerals, like chalk (also known as gypsum, calcium sulfate, CaSO4), are the easiest to make into paints because they’re easy to crush.
Please note: All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.
Here is how you can make your own mineral paint. Wearing a common dust mask, grind a mineral to a fine powder using a mortar and pestle. The mineral can be chalk, clay, red ochre (an iron oxide pigment found in art supply stores), or charcoal. The finer the powder is ground, the smoother the paint will be. Pour the powder into a shallow bowl and add a few drops of water; stir with the pestle until it becomes a smooth paste. A binding agent is needed to stop the paste from drying out to dust. You can use white craft glue for this, or a very clean egg yolk (separate the yolk from the white and gently roll it in a kitchen towel to clean it). Add the binding agent in about a 1:3 ratio of binder:paste, and stir with a mixing stick.
Imagine you are in prehistoric times as a cave painter using your handmade mineral paints. Use clay or red ochre for the red paint, chalk to make white paint for highlights, and charcoal to make black outlines and shadows. The paints used in the finest cave paintings 17,000 years ago were made from these materials. Look up cave paintings in books or on-line to find an original you want to copy.
Pigments and dyes create intense colors. Dyes dissolve in water and soak into fabrics, coloring them throughout. Pigments don’t dissolve, so they are ground into powder and made into paint. Azurite was once an important source of blue paint; it is a soft, deep blue copper carbonate mineral: Cu3(CO3)2(OH)2.
Tips: Dip your paintbrush in water if your paint starts to dry out. Wear a dust mask in case some mineral powders are an inhalation risk; adults should crush very hard minerals for you. Don’t ever use yellow or orange minerals because some are toxic.
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Kathleen Carrado Gregar, PhD, Argonne National Labs
[email protected]
April 2011
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References:
“Rock and Fossil Hunter”, a Smithsonian series book by Ben Morgan; DK Publishing, Inc. NY; 2005; page 32.
