Paleolithic artists used natural minerals to produce pigments in colors such as red, ochre, black, and brown. It is possible that these artists applied some of these pigments directly to the walls with their hands, but hollowed bones were likely used to spray paint onto the walls. Pigment-covered hollow bones have been found near some of the paintings by archeologists. Other tools include chunks of moss or animal hair that would have served as a type of paintbrush. For carving, pieces of flint were used to make engraved lines.