In the late 60's my ceramics class did a Japanese Raku tea ceremony. We didn't have a charcoal fire, we used a small kiln. The cups were made by hand with Raku clay just as they were in the ceremony in the 1500's. They were taken out of the kiln red hot. They sat and cooled down to the point they could be dunked in a bucket of water. We didn't glaze them with a lead glaze like the original ceremony. They all survived even though everything was rushed, it was only a hour class. Denice