Steamer
Japanese: 蒸し器（むしき）
Tool for steaming soybeans or rice. Heats uniformly with steam power.
A steamer boils water in the lower tier and heats food above with steam. In miso making, used for steaming soybeans and rice for koji.
Steaming's advantage: food does not contact water directly, so nutrients and umami do not leach out. Metal stackable steamers are common, but bamboo seiro with good ventilation are also used. Capacity is limited, so split into multiple batches or use a pressure cooker for large quantities. Steaming guidelines: 3-4 hours for soybeans, 40-60 minutes for koji rice. Accurately judging doneness affects all subsequent steps. Steaming technique is fermentation's foundational skill.