Q: I want to make some clay pipes for smoking. What clays are best for resisting heat? How do you get that long tunnel to go down the stem? And how do you sculpt on them without mashing them up?
A: The traditional clay pipe, the “churchwarden”, is cast from a white earthenware clay. It is not glazed, and is fired at a low enough temperature to retain its porosity. While not very durable, they are supposed to smoke very well, and are cheap enough to replace when broken or clogged. Most clay bodies will work for making pipes, though—I believe those elaborate Bavarian pipes with metal lids are made from glazed stoneware. I’d say any clay that can withstand firing can deal with the gentle heat that slow-burning tobacco generates, but non-vitrified clays in general withstand heat-shock better. If you do have a problem with pipes cracking when used, you might increase the proportion of fireclay in the body, or add talc.
If you are going to cast them, you don’t have to worry about hollowness—the slip leaves a void when you pour it out of the mold. The trick is to get a layer built up which is not so thick as to close up your “tunnel”. If you are hand-building them, you can form the stem around a metal rod. Try a little water lubrication on the rod before extracting it.
If you’re having difficulty in sculpting the wet clay, try leaving it to dry a bit after you form the major masses, then burnishing the surface with smooth modeling tools. I made a lot of elaborate pipes using one of those aluminum pipe-tamping and scraping tools to model the surfaces. If you let the clay dry to a “leather-hard” state, you can carve it with sharp tools. If you don’t get along with clay, you can make your original out of something else—wood, soapstone, even soap—and then take your mold from that.