These pots were fired in a container called a saggar, with weeds, grass and other materials to make interesting marks. They are decorative art pieces and not meant to hold liquids. There is a good article about saggar firing in Wikipedia (https://en.wikipedia.org/wiki/Saggar)

sag1 sag2 sag3 sag4 sag5
sag6 sag7 sag8 sag9 sag10