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Firing Rocks With Clay Sculptures?


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#1 Tyler G

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Posted 05 May 2011 - 05:23 PM

I recently heard of people doing this and I am wondering if anyone has any knowledge about this or could point me in the right direction.

Im interested in both materials and firing temperature that would have rocks melt and or stay formed, just curious as to any information about this

thanks

#2 Lucille Oka

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Posted 05 May 2011 - 06:08 PM

I recently heard of people doing this and I am wondering if anyone has any knowledge about this or could point me in the right direction.

Im interested in both materials and firing temperature that would have rocks melt and or stay formed, just curious as to any information about this

thanks



About thirty years ago I fired a stone, not a rock. It was not embedded in clay just sat on a kiln washed shelf. It was a pale Carnelian Agate. I had read somewhere that the stone's color would intensify if heated. I did not bother to find out the proper temperature. I sent it up to Cone 05. The stone did not melt but lost all of its color and looked like chalk but the shape was unchanged.
If you are planning to do rocks which are a composite of many minerals many things can occur in the kiln. Things may pop and shatter.

I recommend using a small rock for testing in a small test kiln. If you do this test in a saggar it will help to protect the kiln, just in case.


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#3 Tyler G

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Posted 05 May 2011 - 06:22 PM

i suppose i meant stones or pebbles more so then a large rock...doing a test in a saggar sounds like a good idea thanks

#4 JBaymore

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Posted 05 May 2011 - 06:59 PM

Hi Tyler.

I do this all the time. It is a part of my basic clay bodies. The usual "rock" is one of three things..... flint, feldspar, or granite.

Flint does not melt. The chunks sort of get lightly softenened edges. But mainly remain whitish lumps withi the clay as the clay body shrinks around them.

Feldspars do tend to melt, and the particular type of feldspar affects how much. The larger the chunk and the faster the firing, the more intact it remains at orton cone 9-10. Small chunks can turn to little whitish glazz blobs. Under shizenyu (natural ash glaze in a wood kiln) thay can belnd interestingly with the deposits. Under applied glazes they can add visual texturing.

Granite is sort of between the two.

Hope this helps.

best,

....................john
John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#5 Marcia Selsor

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Posted 05 May 2011 - 07:55 PM

I had a student rake some sandstone 6-8" some bigger with glaze several years ago. I think it depends on your type of rock. Some may explode.
Could be hazardous.
Marcia

#6 Tyler G

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Posted 06 May 2011 - 07:20 AM

thank you all, i am excited to try it this summer, didnt wanna damage my mothers kiln tho Posted Image


any advice pertaining to cone 6 would probably be most useful right now since i wont likely be firing to cone 10 for a few months or more


i truly appreciate the advice and think this forum will be a valuable resource for me, i will be sure to post results when i get around to trying some stuff but plz continue with any input, thanks

#7 Marcia Selsor

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Posted 06 May 2011 - 08:51 AM

Best advice for switching to ^6 is for you to read mastering Cone 6 Glazes.
If using an electric kiln, the firing schedule and slow controlled cooling makes a very significant difference.
Iron reds can be beautiful in electric is fired right.
Marcia

#8 DAY

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Posted 07 May 2011 - 06:49 AM

By all means, fire in a saggar- which can be nothing more than a piece of old kiln shelf and a bowl that didn't pass the aesthetics test.
And remember, clay IS rock!

#9 Amy Waller

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Posted 10 May 2011 - 08:12 AM

Here are a couple more thoughts to add to this thread. First, glazing started thousands of years ago with the (possibly accidental) glazing of stones. This was in Egypt and elsewhere in the ancient world, and the stone was steatite, a form of soapstone. Alkaline glaze adhered to the steatite when it was fired. Steatite is soft, and they carved the stones to make beads, amulets, statues, and other items before firing them with the glaze. Firing the steatite made it harder and stronger, and sometimes the steatite was fired without glaze. The firing temperature was under a 1000 degrees Celsius, so it doesn't address your cone 6 concerns. If you do a google image search, you can see lots of examples.

On a completely different note, there is a lot of information about using gemstones with PMC (precious metal clay). The stones are fired with the PMC either in a kiln or with a torch. Again the temperatures are nowhere near cone 6, but I've seen several charts with information about how different gemstones fare with being heated. Here's one published by Rio Grande:

http://www.yourriogr...20gemstones.pdf

Good luck and let us know how it goes!

#10 Tyler G

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Posted 10 May 2011 - 11:07 AM

Here are a couple more thoughts to add to this thread. First, glazing started thousands of years ago with the (possibly accidental) glazing of stones. This was in Egypt and elsewhere in the ancient world, and the stone was steatite, a form of soapstone. Alkaline glaze adhered to the steatite when it was fired. Steatite is soft, and they carved the stones to make beads, amulets, statues, and other items before firing them with the glaze. Firing the steatite made it harder and stronger, and sometimes the steatite was fired without glaze. The firing temperature was under a 1000 degrees Celsius, so it doesn't address your cone 6 concerns. If you do a google image search, you can see lots of examples.

On a completely different note, there is a lot of information about using gemstones with PMC (precious metal clay). The stones are fired with the PMC either in a kiln or with a torch. Again the temperatures are nowhere near cone 6, but I've seen several charts with information about how different gemstones fare with being heated. Here's one published by Rio Grande:

http://www.yourriogr...20gemstones.pdf

Good luck and let us know how it goes!



cool history on steatite, im gonna that out more


I could fire lower then cone 6, but not higher I just would think testing stuff at a temperature that I wont be firing other work to would be inefficient so cone 6 would be ideal



thanks for the link, synthetic gems could be pretty cool to experiment with but arent probably my style








#11 macdoodle

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Posted 11 May 2011 - 12:19 AM

fellow newbie - i sent a PM if you want to see a pic of a small stone off park road mostly granite/clay/sand/ glass "technique piece." Most on wet clay- stone sand glass engobes bisqued, then some more glass added in spots some glaze and then fired to cone10 - glass with light crazing also flashed onto rock. Have fun!




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