Pyrography

Pyrography or pyrogravure is the art of decorating wood or other materials with burn marks resulting from the controlled application of a heated object such as a poker. It is also known as pokerwork or wood burning.

The term means "writing with fire", from the Greek pur (fire) and graphos(writing). It can be practiced using specialized modern pyrography tools, or using a metal implement heated in a fire, or even sunlight concentrated with a magnifying lens. "Pyrography dates from the 17th century and reached its highest standard in the 19th century. In its crude form it is pokerwork." 

^{Source: https://en.wikipedia.org/wiki/Pyrography}