Let me be the last one to wish you a Happy New Year!
The last couple of weeks were great, but it's time to get back to the grind.
Fear not, however, I did do a lot of research over the holidays that lead to some interesting ideas...
While at my parents' place for a portion of the holidays, I came across some pottery books (Mom's getting interested in pottery again). Being that my parents live on a small island (Gabriola) there's not a heck of a lot to do to stay entertained, so I read the pottery books. Half-way through one of them, the light-bulb over my head came on (well, dimly flickered at least) and I had a minor 'eureka' moment: I realized that potters have been dealing with much higher temperatures than required for melting aluminum for thousands of years and there had to be a vast knowledge-base I could tap into.
After hours of reading and surfing the net I've decided:
1. in the pursuit of an inexpensive material that's reasonably resistant to high temperatures, cement mixed with refractory clay isn't well-suited (not to mention the propensity for cement to explode when heated to high-temperatures if there's any remaining moisture in the cement)
2. potter's clay comes in many different types, but all of them have one thing in common: after being fired at up to 2200 degrees F, it becomes very tough. It's also cheap and extremely easy to work with (and fun too!).
3. I already had my styrofoam molds made up to shape the firing chamber of my smelting furnace and didn't think it would be too hard to use them to shape potter's clay instead of using cement.
I've decided to form my smelting oven's firing chambers out of clay.
I found a local suppler of pottery supplies (www.greenbarn.com) and decided to pay them a visit. They had some clay that they were discontinuing and I was able to buy a 50lb box of it for $10. Definitely a good start.
While wandering the isles, however, I really hit paydirt: an $85 pyrometer kit that goes up to 2500 degrees!
The kit came with the guage, a 6 foot length of special wire, and the thermocouple.
In hindsight, it's not much of surprise that potters would have this kind of stuff readily available. They also have these cool things called pyrometric cones. They soften and melt when heated and come in a wide range of temperatures. I am surprised, however, that during all the research I did on backyard foundry, no one mentioned hitting up a pottery store for some information/supplies. You've read it here first! (I'm sure I'm not the first )
I took my new box of clay to my shop and got down to work. I laid out 3/8" strips of wood in parallel so I could roll out the clay to a fixed thickness that I'm going to use for the walls of the firing chamber:
I made a tool to cut off chunks of clay with some wire and two aluminum rods.
Rolling out some clay. I used a sophisticated tool called a 'rolling pin'. Very rare and hard to find.
I learned to score the clay where it's going to be joined to more clay to promote adhesion. I also made a mix of slurry to use as 'glue'. Slurry is just clay that's been mixed with water to the point it's similar in constancy to pancake mix.
Carefully working the clay sheet over my styrofoam mold I formed the lower firing chamber.