I decided yesterday to try my hand again at a smaller opening closed form, the last one wasn’t running true and I put a hole in the one side. This one had a few hairline cracks when I started but more developed as it got thinner. I didn’t want to chance making the walls any thinner as I was concerned that the whole piece would blow apart. I actually like the cracks, gives it an aged look. I am not sure on the type of wood.