Raku generally refers to a type of low-firing process that was inspired by traditional Japanese raku shooting. Western style raku usually involves removing the pottery from the kiln while the piece is very hot and bright red and placing it in containers containing flammable materials. Once the materials are ignited, the containers are closed. This produces an extreme atmosphere of reduction that affects the colors and clay bodies.
Acute heat shock also produces cracking (known as crackling since it is intentional).
It is not recommended to use the bowls for food and drink, but they are used for aesthetic purposes only, because of the cracking that occurs to the piece, peeling of the glaze layer may occur.
Burning raku needs dedicated ovens and an open place, so you must be prepared when you take out the piece and put it in flammable materials for a huge amount of smoke.