So I've been adding stones and also turning the stones over. Just turning them over kicks up the heat because... [rock explodes] Hand-grenade stone. I'm okay. That's an important point. Sometimes you have rocks that soak up a lot of water, you don't want to put them in the fire because they will explode. That was one that just blew. If you have river stones, you want to keep them out of the fire because they will have water inside. The water will build up pressure in the form of steam, and they can explode.These stones I thought were pretty safe. They are river stones though, but obviously one of them did kick up and pop. That shrapnel can be pretty dangerous. You want to make sure that when you're cooking with river stones you don't have something that's going to explode on you like one of them seems to just have done. Fortunately I came out alive.