Washing the fresh natto grass clean, I spread it on the bottom of the vat. When the soybeans no longer felt hot to the touch and the temperature was not too high, I poured them into the pottery jar, wrapped them with the natto grass, piled a heavy stone on top, covered it with a cotton cloth and waited for fermentation.
I took the water used to cook the soybeans, added salt to it, and set it aside in the space for later use.
Normally, fermentation should not exceed three days – to keep the temperature around thirty degrees for fermentation. I placed the pottery jar on the heated brick bed, albeit at the rear where the temperature is a bit higher than in the middle, but still not too hot to handle.
By the fourth day, the fermenting soybeans could stretch into transparent threads, a sign that the process was complete.
