Part of my continuing effort to learn “caveman chemistry” through Kevin M. Dunn’s book of the same name, Caveman Chemistry. One of the upcoming chapters of work for me is the creation of a crucible which can serve as the key operating tool of four mastery projects — the smelting of metal from ore, the creation of lime from stone, the creation of glass from silica, and the firing of ceramic. The last of these is actually the most important; if I can’t do that, then I can’t really do any of the other three.
Maybe it will get the job done… maybe it won’t.
So, this is my first attempt to shape and create a crucible. And this entry that accompanies it are some of my lab notes on the project. I bought a kind of clay from Michael’s arts and crafts store called CraftSmart® natural clay. My friend Albert, a master potter, is really concerned about firing it. It handles like clay, it looks like clay, it sorta smells like clay… but it was in a box without firing instructions, and with really unclear directions about how to dry and prep it for firing.
I laid out a copy of my monthly Connecticut Freemasons newspaper (seemed appropriate) after reading it, as the surface for working. I first made a pinch-pot, which you can see in the background, that became too large and unwieldy too quickly. A crucible has to be formed from one lump of clay without air bubbles; the one in the back became too wide too quickly.
So I cut a new ball of clay, and prepped it as before. I shaped this crucible from a single piece of clay in the form (as the book instructs) of a chalice with a foot. Mine isn’t as pretty as other people’s, or the one shown in the textbook. I think it will serve, though. The walls are a centimeter thick or a little less, including in the foot. It’s pretty much a pinch pot, and though it still needs some smoothing with a spoon after it’s bone dry, it should fire well (assuming this kind of clay can be fired to cone 06, which isn’t clear).
Once the crucible was formed, I let it dry for a couple of hours, and then I formed the lid. The lid has to be formed before the crucible body was fully dry, because clay changes shape as it dries, and shrinks quite a bit as it does so.
an earlier page-set from my ‘lab notebook’. If it’s worth doing well, it’s worth doing over-the-top
The lid is in the form of a dish. This is so that, when it’s in the kiln with some chunks of malachite (for smelting copper) and some charcoal inside as well as in the lid, along with some investment material, the crucible will focus and store heat and melt the malachite into a small copper ingot. This is the theory anyway.
Before any of this can happen, of course, the kiln has to have its way with the crucible for the first time — to drive out the excess water, and functionally change the chemical structure of the clay, to vitrify it. And I’m hoping that the whole structure will survive vitrification, but there’s no guarantee. The lid may break, or the crucible, or both. They may survive the firing, but not get fired at cone 06. A lot can go wrong. We’ll see.
Progress to Date
I had hoped that I would be able to complete considerably more projects in “Caveman Chemistry” this summer, and really ramp up my skills. Alas, life has sort of gotten in the way in a number of ways. I’ve managed to start fires with a bow drill, make an arrowhead, learn to work through Unit Factor Analysis problems, made mead, and now created a crucible (even though I haven’t fired it yet). I’ve also made a few beautiful pages in a medieval-style grimoire-book of the relevant chapters and exercises, as a way of learning the work more effectively (though not necessarily efficiently). Progress made, not finished. Five steps is better than zero steps, it’s not as good as twenty-eight steps. Still, there was some cheese-making in there too.