Getting right to it this morning, I made some modifications to the lower firing chamber's mold. Knowing now that I have to get the mold out of the clay as soon as possible to prevent the clay from splitting again, I cut the mold into 3 parts. By shaping the centre part like a wedge, it should be easy to pull it out of the clay, allowing the other two parts of the mold to come out easily.
I lined the two sides of the centre section with clear packing tape to allow it to slide out easily.
Once I'd done that, I proceeded to lay the clay out on the mold. It gets a lot easier and faster the second time around
I'll leave the clay on the mold for about 36 hours, just enough for it to dry to the consistancy of leather, before I remove the mold.
Well a bit of a disappointment when I came into the shop today, but another lesson learned: clay shrinks when it dries.
I had left the clay around the form thinking that it would dry out and I could remove the stryofoam later.
After I removed the styrofoam, I put the pieces back together to see how the lower firing chamber would look like. I'm pretty happy with the results.
Fortunately, the upper firing chamber hadn't dried quite enough to start cracking so I removed the styrofoam mold (the black stain is from where I had to burn out some of the styrofoam with a torch).
I was very happy how this form turned out. In another week or so it should be ready to be fired in a kiln.
The small hole at the back of the chamber is where the pyrometric probe will be inserted. The bump in the middle serves two purposes: it reflects the incoming flame from the burner down to the aluminum to be melted and it protects the pyrometric probe from direct exposure to the flame.