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Pottery at Pete's

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Zuma:
Ruddy,I think you would fit in quite well :) Yes the hearth aspect of the firing is fascinatingly different.
That's one aspect. The other was actually hydrating the clay with
the stream water. But more than that was our elfish instructor
Keith. Most of our group met Keith for the first time. As did the
check out clerk at the grocery Keith stopped at on his way to House Mt.
She said "Your not like us are you?" He said "No I am from the forest."
He told us "She was still laughing hysterically as I went through the auto doors."
Keith is from the forest, totally off the grid, but college educated and
a real quality guy. I have know him for about 20 years and love em.
Zuma

iowabow:

--- Quote from: nclonghunter on July 06, 2016, 10:16:42 am ---Hey Zuma, probably wont get there until Saturday morning. Tom is bringing some items he made and I have one drying from his clay also. Hope to do a pit firing Saturday evening or Sunday with what folks bring. If Keith is okay with it.
I cooked and crushed some shell and added it to some local clay early this year. Fired the pots and they came out looking great. After about a month or so I noticed some cracking and noticed the shell was getting soft and appeared to be expanding. The pot eventually fell apart from the shell expanding. I believe it started pulling in moisture. I also believe I did not crush the shell enough. It may need to be close to sand in size. The pot that cracked is now pounded and crushed into grog and may add it to the clay this weekend. I will also bring the other one for you to look at. It is still intact but has pieces popping off. Again, worst in wet humid weather. Maybe if you cooked in it regularly it may not happen but I do not know.

One thing I read is after you cook the shells, wash them before crushing. Not sure why unless it is to remove ash and dirt from the surface.

See ya soon!

--- End quote ---
Calcium carbonate oxidation occurs with heat. Key word here is oxidation. This creates calcium oxide add h2o you have calcium hydroxide. The addition of water increases mass.
A pot with shell will self destruct unless you control this equations. Reduction is the key don't oxidize and the pot will not blow up. How do you do that you might ask...keep the pot buried under a high carbon environment. This will allow the pot to sparkle. I discovered this process after many experiments. Preburn is an other subject altogether that i could explain if you like.

Zuma:
 Thanks Iowa.  :)
So are you suggesting the shell
tempered pots would be better off pit fired?
As opposed to the open air log/kiln type firing
in the photos.
Zuma

nclonghunter:
Wood burning gives off carbon if I am not mistaken. I am leaning more to a pit fire for shell tempered pots that is filled with and covered with chopped bark or sawdust to both give off a slow and low heat and more carbon. Those pots we filled with pine bark were black inside from the carbon, which is also suppose to help seal and waterproof it for cooking. I think Keith called it shell bloom or something like that. Before Keith's class I had two shell tempered pots that took in moisture from the air about a month after firing and started cracking and pretty much fell apart. All due to the shell swelling. Sand tempered or quartz tempered pots will not have the same nature as shell so a safer bet.

iowabow:

--- Quote from: Zuma on August 07, 2016, 09:22:42 pm --- Thanks Iowa.  :)
So are you suggesting the shell
tempered pots would be better off pit fired?
As opposed to the open air log/kiln type firing
in the photos.
Zuma

--- End quote ---
The powder that he discribed is absorbing mositure from the air and is lime popping. This happens do to expansion. The expansion is a natural continuation of the chemical reaction.
The reduced atmosphere can be achived in other types of firing processes i.e. propane, gas, or wood as you stated. If you would like I can post a picture of a pot that has both example in one pot. Only half of the pot was reduced the other half was oxidized.
Yes you are correct the pit fire will work if you create the environment within the pit correctly.

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