I found this interesting video about fire bricks vs red clay bricks

I found this and just wanted to share. I thought all you needed was a brick that could handle the hot temperatures. Turns out thermal shock is a thing and is why old ovens were fired over the course of a week! In the video he does a thermal shock test with 3 bricks. It was quite interesting.

https://www.youtube.com/watch?v=X-M-2ZrmHDc