There's one other thing I'll mention about compression, and it relates to making large bowls (which I'll talk about in more detail in another blog). I've seen many potters use a torch to harden the clay near the base when they're throwing large bowls with walls that spread out widely. There's no need to do that. If you use ribs on both sides of the wall and don't add more water or slip, you'll line up the clay particles on both sides of the wall which will make the wall stronger. The thinner the wall becomes as you stretch it out, the higher the proportion of clay particles that are lined up together which allows you to bring the walls out even farther. Using this technique, you can almost lay the walls out flat without them falling down.