# Strange Hotplate Discovery



## Auggie (Feb 13, 2014)

I didn't know exactly where to put this, whether under Safety, or Systems & Tools, but I think it's most appropriate here, because perhaps this "discovery" can be useful for constructing electric furnaces.

Because it is now apparently lawful for a corporation with a fraudulent chain of title to foreclose on a mortgage, I am presently domiciled in my warehouse, and as I fought until the bitter end without giving any thought to a Plan B, the change of environs was swift. I quickly improvised a "kitchen" using implements I had on hand, including a Corning PC-35 hotplate for my cooktop from my lab equipment stash. It works rather well for cooking and has filled many a hungry belly of mine. Because it tends to heat up slowly I almost always just crank it to maximum temperature (which according to the setting is about 500 degrees C), put my pan on it and wait for ignition, then I get cooking.

According to the description it has a ceramic surface platform. Here's what it looks like:

http://www.biosurplus.com/store/products/5006258-corning-pc-35/

One evening I had turned on the hotplate and got distracted somehow. I had a lid for a pot in my hand and placed it directly center on top of the hotplate surface because I was planning to just be gone for a moment. The lid, about 8" in diameter, covered nearly the entire hotplate surface, with just a small amount of the outside corners of it exposed. It was by no means air-tight, as there were gaps where the lid hung over the surface.

I ended up being gone for a lot longer than a "moment" and in fact forgot how long it was, but it could've been around five minutes. When I returned, I went to lift the lid from the hotplate so I could put down the pan. To my surprise (and minor shock) the hotplate surface was starting to glow red. I marveled at it for a bit, wondering why the hotplate hadn't already self-destructed, but then quickly put my pan down on it to start cooling it down. I cooked my meal that evening without further incident.

Ultimately, nothing seems to have happened to the hotplate. In fact, I'm eating the scrambled eggs I just cooked on it as I write this.

So now we turn to the point: what practical knowledge, if any, can come out of this? If these hotplates can withstand, say, 2100F, then perhaps it's possible to construct a quick & dirty furnace for melting PMs by placing a crucible on top of a hotplate, covering it with a conical lid, then cranking up the hotplate to full temp. I don't want to experiment with mine because I need it to cook my eggs, but I was wondering if anyone might have any insight on this?

How hot can that ceramic surface get before it fails? How hot can that hotplate drive the ceramic surface before it fails? Did I only re-"discover" something already known? If so, has it already occured to people to attempt this? Has anyone tried?

Anyway, take it for what it's worth.


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## etack (Feb 15, 2014)

I would say it depends on how thick the Pyroceram top is.

Some interesting specs on Pyroceram in relation to thickness.

http://www.woodstove-fireplaceglass.com/Pyroceram.html

Looks like it wont go that high unless it was .5 inch thick or so.

but the heating element might. get some high temp insulation and some kiln wire and make it and not trash a high dollar heating dish.

Eric


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## niteliteone (Feb 15, 2014)

Just remember that ALL electrical devices are rated at their "sustainable and repeatable" performance abilities as they were designed.
If you exceed those ratings you risk device destruction or worse :shock: 
Most will tell you "once you release the smoke you can't put it back" :lol: 
So always use devices as they were intended or be ready for what could happen. The second part is not recommended.


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## bmgold2 (Feb 15, 2014)

Interesting topic. I wouldn't want to risk destroying that hot plate but I wonder if something else like an oven heating element might work? I have an old electric kiln that the element burnt out in. It was just basically an insulated firebrick box with a heating coil pined to the walls. I had it up to almost 2000 degrees F. when the element burnt out while I was firing some pottery. It was actually made for doing assays and held probably 3 or 4 crucibles at a time. I never did get it to work for assays but that was probably due to impatience on my part. I haven't checked in a while but replacement parts are probably still available for this furnace. I think I got it from Action Mining 5 years or so ago. I've also thought of turning this little furnace into a propane fired furnace for firing pottery but I'd assume that it would also work for smelting or melting gold or silver with the right burner.


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