Primitive Technology: Grate furnace, wood fired smelting experiment

Description :

I built a furnace from bricks with a grate to admit air that ran by natural draft and used wood fuel instead of charcoal to smelt a cylinder of iron ore and charcoal powder placed on the grate. The grate had a hexagonal cross-section and the furnace was made from bricks. The furnace was 1.5 cm tall when finished and about 50 cm wide internally. The ore brick was placed on a small pot filled with twigs in the centre of the grate so that it would melt into the pot. A crucible was not used because there is no clay refractory enough to withstand the heat here. The furnace was filled with wood. A fire was lit from the bottom up and the whole thing burned for about 2 hours. The ore brick had indeed melted but fell over during the smelt so the slag and iron didn’t flow properly. The pot it was meant to melt into melted apart and caused the ore brick to topple. But the ore brick still did melt and some iron prills were visible but were too small to bother collecting. The ash from the firing was made into ash pellets for mortar production that will be used on another project I’m working on. The furnace has potential, no labour is used during operation (no bellows or blower), no charcoal is needed though the wood must be cut to small pieces and a high temperature can be attained so that ore is melted.