Onggi

Onggi are traditional Korean earthenware vessels that have been used for centuries to ferment and store kimchi, soy products, and other staple foods. Unlike glass or plastic containers, onggi are made from a porous clay body finished with a natural glaze, which many practitioners believe allows a small amount of air and moisture exchange through the vessel walls during long, slow fermentation.

A typical onggi crock is wide-bellied with a narrower opening, a shape that helps limit the surface area exposed to air while making it easier to pack vegetables down firmly with the hands or a weight. Because they are unglazed or lightly glazed on the interior in some styles, onggi need to be seasoned and cleaned carefully, and many are quite heavy compared to glass jars of a similar capacity.

First-time buyers sometimes assume any large ceramic crock is an onggi, but authentic pieces are specifically fired and shaped for fermentation, with quality varying a lot between decorative pottery and functional kitchenware. Checking that a crock is described as food safe and intended for fermentation, rather than purely ornamental, is an important step before using one for kimchi or sauerkraut.