Calcium carbonate CaCO3 is a natural substance found in rocks and deposits as the minerals calcite and aragonite, but mostly as limestone, which is a type of sedimentary rock that consists mainly of calcite. It is the main component in e.g. eggshells, snail shells, clam shells and pearls. 4% of the earth's crust consists of calcium carbonate, so it is a very widespread and available substance and is included in countless products.
Calcium carbonate is a white, odorless powder that may resemble fine flour, but slightly heavier in density. It is easy to mix with water and is suitable as a filler in paint. In oil, the next becomes colorless. In water it will become more opaque.
Filler for linseed oil paint
Filler for Wall Paint
Filler for Making Gesso (primer for painting)
Filler in putty
Use in painting
Marble flour is used in painting as an addition to primers and as a filler in fresco painting. As marble flour mixed with oil is largely colorless, it is also used by oil painters for various techniques, as it can be added to the colors and only very slightly lighten them. Marble flour gives more body to the oil colors and is therefore suitable for an impasto effect. Marble flour makes the colors more transparent and thus allows the underlying colors to shine through.
Oil, resin and wax are also used to make oil paints transparent, but the mentioned coloring agents affect the paint and the colors and make them runny, glossy matte etc. As marble flour functions as a largely colorless pigment, it can be used as a coloring agent, where the paint's viscosity and gloss should not be affected. Marble flour can be mixed directly into the oil colors, or a painting agent can be made, where the marble flour is worked together with, for example, linseed oil or walnut oil to a suitable consistency.
It is known that Rembrandt used marble flour in his techniques
Calcium carbonate is described as non-toxic.