pigments had been obtained, they would be ground and mixed with a liquid, such as water, blood, urine, or egg yolk, and then applied to the stone as paint using a brush, fingers, or a stamp. Alternately, the pigment could have been applied on dry, such as with a stick of charcoal. In some societies, the paint itself has symbolic and religious meaning; for instance, among hunter-gatherer groups in California, paint was only allowed to be traded by the group shamans, while in other parts of North America, the word for "paint" was the same as the word for "supernatural spirit". One common form of pictograph, found in many, although not all rock-art producing cultures, is the hand print. There are three forms of this; the first involves covering the hand in wet paint and then applying it to the rock. The second involves a design being painted onto the hand, which is then in turn added to the surface. The third involves the hand first being placed against the panel, with dry paint then being blown onto it through a tube, in a process that is akin to air-brush or spray-painting. The resulting image is a negative print of the hand, and is sometimes described as a "stencil" in Australian archaeology. Miniature stencilled art has been found at two locations in Australia and one in Indonesia. Petroglyphs Petroglyphs are engravings or carvings into rock which is left in situ. They can be created with a range of scratching, engraving or carving techniques, often with the use of a hard hammerstone, which is battered against the stone surface. In certain societies, the choice of hammerstone itself has religious significance. In other instances, the rock art is pecked out through indirect percussion, as a second rock is used like a chisel between the hammerstone and the panel. A third, rarer form of engraving rock art was through incision, or scratching, into the surface of the stone with a lithic flake or metal blade. The motifs produced using this technique are fine-lined and often difficult to see. Rock reliefs Normally found in literate cultures, a rock relief or rock-cut relief is a relief sculpture carved on solid or "living rock" such as a cliff, rather than a detached piece of stone. They are a category of rock art, and sometimes found in conjunction with rock-cut architecture. However, they tend to be omitted