Summary

Raku is an ancestral Japanese ceramics technique. When you use this technique you open the kiln at approximately 1000ºC, and once ready the pots are removed from the kiln with metal tongs and smoked in a closed container – the clay then undergoes a thermal shock and, when in contact with air, the hot glaze fissures, cracks.
 
The hot pots ignite the sawdust and newspapers put beforehand in the container. Since the container is closed, when the flames choke they will seek to extract oxygen from the terracotta to remain alive for a few seconds more.
 
This is called a REDUCTION. During the reduction, the pots blacken and the colors of the glazing are revealed.
 
When the pots have cooled down for about half an hour, they are extracted from the containers and sprinkled with cold water. This widens the cracks of the enamel.