Yes she does. Nice to be reminded of it. As I said, I used to fire gas by color alone. However the point that most of us were trying to make is that if you are having problems with your firing, having cones to check your heat work, certainly makes the problem solving much easier especially when the conversation is started out with -
"I do think my oven's thermometer might show a bit higher than it actually is, so maybe just increasing to 1060 or 1070 would help."
Cones are only a tool. They do not make the pudding - they make replication and problem solving easier (not to mention safety). While I agree with Bob that with a good controller you don't need cones, I still say that they make problem solving much easier and that was what this whole thread started out as. Donna
I love the German look by the by. I don't know why my grandmother didn't have it. Donna
Good points! But how about if he used a *clay* box? To the OP: In the pottery world a "saggar" is a box made of clay slabs to hold pieces that you don't want to be exposed directly to kiln flames, or to contain a special environment around the pieces, They are typically sealed with some sort of soft clay for the firing, just as you wish to do.
You can make your own clay slabs by rolling them out with a rolling pin on a canvas-covered board. Lay down two strips of wood on ether side to hold the rolling pin up by the desired thickness of the clay. Probably 1/2 inch slabs would be good, depending on the size of the box.
The slickest way to do this is to make a template out of tarpaper (roofing felt). Moisten the back of each template piece and roll it onto the surface of the slab... it will stick. Now cut out the clay by running a tool around the template edges... a "pin" tool (like a smooth-tipped needle on a handle) is ideal for this, but even an old smooth-edged dinner knife will work,
To assemble the slabs, use an old toothbrush dipped in water to scuff up the joining faces so they are rough and sticky, then press the pieces together. Leave the tarpaper on to give stiffness during this assembly. (Which means you want to design your template so the tarpaper ends up on the outside.) The scrubbed clay slurry should ooze from the seams a little. Smooth it out, and maybe smear a nice fillet on the inside using additional soft clay.
Let this set up a bit, then carefully peel off the tarpaper. Drape plastic loosely over it to prevent it drying too fast, and rearrange the plastic every day or so. When it seems to be pretty hard all over, remove the plastic and let it get absolutely bone dry.
You will should fire this saggar once before you actually use it for case hardening. Set the lid in place when you do this, to help keep it from warping differently than the rest of the box. Fire to at least cone 04 (roughly 1050C), though cone 6 (1200C) might be better.
While I've made plenty of clay boxes, I've never actually used one as a saggar (not much need for most electric potters). So one thing I'm not sure of is what sort of clay mix to seal them with. I *suspect* that if the box has already been fired, you can use the same clay to seal it with. I don't think you should let this dry first, just smear it on and start the firing. However, someone with saggar experience may have better advice... you might want to mix in some sand or some other refractory filler with the clay, for example.
Best regards,
Bob Masta DAQARTA v3.50 Data AcQuisition And Real-Time Analysis
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I *think* so, as long as the box was adequately vitrified beforehand. But as I have no metallurgical experience since college (back when dinosaurs ruled the Earth), I can't say for sure. However, I have heard of this basic technique being used to maintain a reducing atmosphere around pottery in an electric kiln (by including combustibles in the saggar), so it seems at least feasible.
Best regards,
Bob Masta DAQARTA v3.50 Data AcQuisition And Real-Time Analysis
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