The Incubator

I built the cabinet in January 2026, using Douglas Fir timber from Devon for the main structure, Sussex Oak for the hinges, and Western Red Cedar from Devon for the three koji trays that rest inside.

There are no metal parts or glue in the incubator - the wood is connected with dowels, hand-carved mortice and tenon joints and tension. Nothing is quite perfect, it has strange angles and needle shaped gaps and it creaks as the wood expands and contracts, but it makes the perfect conditions for koji to grow and it smells amazing.

A small blow heater and humidifier inside regulate the environment for around 6 kilos of koji to grow happily over the 48 hour grow period.