Onggi, the Brown Earthenware

#Onggi is a #Korean #native language. If #celadon and white #porcelain are the vessels used by the nobility, Onggi was used by the common people. The look is rugged, but in terms of function, it is ahead of the celadon and white. What is the secret of Onggi, who had a hole where air could come in and out to ferment food but did not leak?