Main Discussion Area > Primitive Skills
Pottery at Pete's
iowabow:
--- Quote from: nclonghunter on August 07, 2016, 09:58:00 pm ---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.
--- End quote ---
remember the purpose of sand and shell....to improve the quality of secondary clay bodies. Sand historically was used first but its disadvantages were two fold. You had to create a thicker pot and was heavier than shell.
Secondary clays that are SHORT tend to crack because the clay platelets are not uniform. The sand or shell disrubt the movement of cracks caused by this poor quality within the clay.
Zuma:
Iowa.
If you have the time---
Any and all info on pit firing is totally welcomed. :)
Thanks, Zuma
Jodocus:
those pics with the drying greenware are candy! thanks for these enjoyable Posts!
Iowabow, I also found I Need to fire strictly reductive when limestone is present in the clay.
As to the tempering, sand tends to have rounded edges, wich is not preferrable, it gives much less stability, especially to the wet pot. You can still use it of course for the sake of the reduced work. It's also quite heavy
when you're firing open or in a pit, tempering partly or fully with plant fibers, coal or wood is great. It reduces the ocurrence of pop-offs and cracks big time. Try sawdust, hay or whatnot, but well degraded horse shit is really best. The sun bleached, rain washed kind, that doesn't smell shitty anymore.
Fiber tempering gives you very tension strong clay, great for working slabs or building thin walled.
An organic temper that comes close to grog is crushed nutshells. heavy organic temper will also help to Keep reductive conditions in the clay.
If you want a non-porous surface, or for subsequent polishing, just put on a good layer of think slip on the still wet pot.
Zuma:
Thanks for your interest and input Jodo.
I need to try some fiber tempering and some slip
application. The shell tempered pot in the other thread
is very light weight. I haven't emersed it in water yet ???
I still have two more to fire and plan to build more.
Zuma
iowabow:
This should help with understanding reduction and oxidation. The black is reduced (shell shinny) the tan was in a oxidizing enviroment and is now lime popping. This is a really cool example.
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