Wednesday, May 27, 2015

What the hell is a 'plinth'?

Somehow during my research on building the furnace, most likely due to my impatience to light some stuff on fire, I completely missed the section on plinths.

Basically, as I've now learned, a plinth is a piece commonly made of refractory material and is set in the bottom of the furnace for the crucible to rest on. Typically they are cylindrical (shaped like a hockey puck) and slightly smaller than the base of the crucible. 

The plinth has two main functions as best I can tell: it elevates the crucible out of the direct flame and it exposes some of the bottom so that it is heated as well.

Gee... that first item sure sounds like root cause of why I'm blowing through the side of stainless steel containers!

I have enough left over material to mix up and make plinths, however I don't want to wait the week plus for them to dry properly (though I should get some going in the background). I lieu of that, I figured I'd scavenge the bits I made from the leftover refractory while originally pouring the furnace. 

If you will recall, I poured most of the leftovers into a coffee can with the intent of making a smaller furnace that I could use for quick jobs. I used a mostly empty propane bottle for the inner portion of the mold which I wrapped in masking tape. My thought process was that the moisture in the refractory would degrade the adhesive on the tape so, once it was dry, the propane bottle would slide right out.

No surprise that didn't work and I ended up with a propane bottle cemented into a coffee can. It did make for a handy torch stand while I used the remaining propane though.

VERY carefully using an angle grinder with a cutoff disk, I cut the coffee can into sections, making sure to only cut through the can and not into the refractory or worse (BOOM!) the propane bottle. I then finished the cuts by hand with a hacksaw blade to make sure I stopped well before damaging the bottle.

Even with cutting them into sections, they still wouldn't slide off the bottle so I had no choice but to break them into several pieces. 

These aren't the ideal puck shape and they are a bit large for my furnace. I'm hoping I can chip them into a proper size and shape to use until I can make more appropriate plinths.

I am a little bummed I won't be able to make a small furnace like I originally planned, more importantly, I didn't blow myself up recovering the propane bottle.

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