bonfire

In ceramics, bonfiring is a primitive but effective method of hardening pottery by stacking pieces around a wood fire in the open air, rather than loading them into a kiln. The pottery sits in and around the flames, exposed directly to combustion heat. Temperatures typically reach 1000 to 1200 degrees Celsius, enough to vitrify earthenware and some stoneware bodies, though not to the cone temperatures needed for porcelain or high-fired stoneware.

The method requires careful fuel layering. Green wood, dried dung, or slow-burning materials like straw are arranged in alternating layers with the pottery to create an even heat distribution. Pieces must be completely bone-dry before firing, or they will crack and shatter. Unlike kiln firing, there is no way to control the temperature curve; the fire burns as it will, and the potter must rely on experience to judge when the firing is complete, usually by observing the color of the ware and the intensity of the flames.

Limitations and surface effects

Bonfiring produces unpredictable results. Ash and embers settle onto the surfaces, creating carbon deposits and metallic specks where they've fused into the clay. Pieces near the flames turn reddish or orange; those in cooler zones remain grey or black. This variation is often embraced as character rather than treated as a defect. The firing atmosphere is strongly reducing, meaning oxygen-starved, which creates dark colors and mottled surfaces impossible to replicate in a controlled kiln.

The technique survives in traditional potting cultures and among artists who value its unpredictability. Raku-style firings and some Indigenous and African pottery traditions rely on bonfire methods. Industrial ceramics manufacturers abandoned the practice over a century ago in favor of kilns, which offer consistency, fuel efficiency, and safety. A bonfire firing requires constant attendance, produces significant smoke, and carries fire risk, making it impractical for production work.