Hello all and thanks to all who responded to my agate stone question. I put 4 small "pebbles" into a bowl, bisqued it to ^04, and to my surprise----when I unloaded the kiln there in the bottom of the bowl were the pebbles just like I put them in. Nothing happened. I'm sure by firing them higher like to ^6, maybe they would have melted, but I doubt it. So much for that experiement. Martha
agate stones in pottery
Oct 28, 2004
6 Replies
I guess you need to know what they are made of, at least mostly and what the melting temperature is for that. Then you would get an idea if they will melt or not.
I just looked up agate in a mineral handbook, and it said it was SiO2.
(silica). Looked up the melting point of pure silica... 1710C. That's about cone eleventy-three, according to my calculations.
Best regards,
Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis
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Bob, I don't have that cone. :>)
Oh dear :o) Another type of stone maybe??
Agate is essentially quartz with impurities that give it the color. As someone else noted, quartz has a very high melting point. Glass is essentially quartz with a sodium salt added which allows it to melt at much lower temperatures, so agate COULD be used as a glaze but with a LOT of work and research. I doubt you want to take the time to do it. Try putting glaze on a test tile with a small agate in the middle. The higher cones the better. The glaze may interact with the agate enough to stick to it. Experiment, experiment, experiment. You will find all sorts of interesting things.
Raj
Cute Bob It's actually cone 32
If anyone here needs info on cones, go right to the source:
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'll need Adobe Acrobat reader to view the files on that site under resources, but the reader is free at :
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's REALLY nice is that you can print them out, and stick copies near your kiln (but not too near, especially if you're trying for cone eleventy three)
Happy Halloween, All Hallows Eve, Samhain, and whatever else you're celebrating this time of year!
Wayne Seidl Key West, Florida, USA North America, Terra Latitude 81.45W, Longitude 24.33N Elevation 3.1 feet (1m)
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