Once I had a book called 'The Breathing crock', and that's a nickname for Korean crocks.
How do they breathe?
Well, they are not extra-terrestrial, but they can breathe because they have breathing holes, unlike other kinds of crocks or jars.
It is a kind of 'Soy sauce crock'.
This Korean crock is made with mud, and is heated to 1300 degrees Celsius.
When it is covered with oak tree lye glaze, breathing holes form on the crock.
However, when it is covered by an artificial glaze made with many different chemicals, the crock no longer becomes a breathing crock.
This specific crock, 'Ongi' is very good at fermenting food, such as kimchi.
Today I read a news article and found this.
(My mom doesn't make kimchi because of that)