Daiatomaceous earth, the material used for shichirin, is heat resistant to take advantage of cooking with charcoal, but on the other hand, it is not very durable. The highly durable Mikawa clay mined in Hekinan City, Aichi Prefecture, was used for shichirin, and production of shichirin in this region became active.
The Mikawa stove is a double-layered black shichirin, but today, shichirin production has evolved over time to focus more on ease of use and appearance. The easy-to-use rectangular shape, the variety of colors, and the iron plate wrapped around the outside make them easy to clean. Shichirin is called Konro in this area, but the performance and products are the same as Shichirin.