Charring

[1] Polymers like thermoset, or most solid organic compounds like wood or biological tissue, exhibit charring behaviour.

[1] Charring can result from naturally occurring processes like fire; it is also a deliberate and controlled reaction used in the manufacturing of certain products.

This is accomplished by either burning the parent fuel (wood or coal) in a low-oxygen environment or by heating it to a high temperature without allowing combustion to occur.

A "coal burning" blacksmith's forge actually produces the heat necessary for high-temperature metalworking by the continuous production and consumption of coke within a carefully managed fire.

This layer then serves to protect the remaining structurally sound core of wood, which can continue to carry the building loads if appropriately designed.

An aerial view of a bearded man in a coat, with a handmade rake, standing on a low, ~10m wide, rounded mound of black earth. The mound is emitting many slender streamers of smoke from all of its surface except the bottommost meter. The steamers merge and stream diagonally away from the viewer on a gentle but chill morning breeze, making an opaques white cloud. The visible background is dark coniferous forest; in the foreground, a glimps of another pile, this one tightly packed wood not yet covered with soil.
A charcoal burner tending his charcoal clamp, in which he is producing charcoal . The process takes days, and the clamp has to be monitored to stop the fire from breaking out (technically, the oxygen from breaking in).
Traditional houses in Naoshima, Kagawa clad with yakisugi panels