Calcite Powder or Calcium Carbonate is an inert pigment of considerable bulk, of use in oil painting only as an extender or adulterant.

When ground in linseed oil to a stiff paste, it does not retain its white colour, but the paste becomes yellowish brown and forms the familiar plastic cement known as putty.

When used with water-soluble mediums, acrylic binders and glue sizes it retains its whiteness: it is invaluable for the manufacture of gesso.