Today, almost all kanten is made by a modern process. This procedure involves the use of sulfuric acid to dissolve the starches, and chemical bleaches and dyes to neutralize the color and flavor. However, a few small producers, such as the Mizoguchi family in the mountains of Nagano, Japan, still use the old labor-intense traditional method.
The natural snow-dried method begins on Japan's coast, where certain red sea vegetables of the gelidium species are harvested in the fall and sun-dried. The dried sea vegetables are bundled and taken up to the Mizoguchi shop to be made into kanten during the cold winter months.
Beginning in December, the sea vegetables are placed in a large cauldron with water and allowed to cook down for several hours. The resulting gel is allowed to cool. It is then cut into blocks, arranged on bamboo trays, and set outside on snow-covered rice paddies. Moisture in the gelatin freezes each night then thaws during the day. In about ten days, all the moisture is gone and the light, flaky bars of pure kanten remain. The crisp, porous, feather-light bars are then shaved into fine flakes and packaged.