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Processing dug clay


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#1 Gavinfine

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Posted 04 May 2013 - 09:43 PM

Hello Everyone,
I am in Illinois and have access to clay in a creek. The clay is certainly earthenware and fires nicely as terra cotta, however, I would like to take it to stoneware temps without it slumping and boiling alive in the kiln. I have had success adding fire clay to the body along with silica sand but the sand eats my hands alive. I would like to switch to silica flour (flint) but am not sure what mesh (200 or 325) and how much. Any suggestions out there? The clay is very high in iron if that helps.

Thanks.
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#2 Marcia Selsor

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Posted 05 May 2013 - 02:42 PM

You could use the 200 mesh silica maybe 10% but to a body with. 30 % or more fire clay or stoneware clay.Add some Ball clay, 20-30% A low fire creek bed clay is probably going to need a lot of help to stay functional at a high temperature. I used red art clay for more color in a stoneware clay but not as any type of structural additive.
I would not have anymore than 20-30% of the local creek bed clay in a stoneware body. Test a lot of combinations.
Marcia

#3 AtomicAxe

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Posted 06 May 2013 - 12:45 PM

When I lived in Florida, I used to dig my own clay ... wonderous stuff too, had lots of sand in it so it was great for throwing and while it was white-ish it turned to a red-ish clay after and was only earthenware clay at best ... but I used it for pit firings so i never needed to worry about the sand or going higher. The few times I did use it for something else, i was meticulous in making it useful in a clay body ... my recipe was:

25% dug clay
25% fire clay
25% epk
20% flint
5% fine grog.

In order to do this recipe, I needed to dig the clay, dry it out, powder it to small pieces, slake to siftable consistancy, sift to 100 mesh (filtered larger sand and other large debris out) ... really not worth it since the time to do this was agonizing and it costs less just to buy ball clay ... but in an area without as much sand or rocks the lake clay will be much easier to prepare for consistant results. In the end I got the clay up to cone 10 and it was pinkish in ox, rustic brown/grey in high fire, but was my go-to for iron bearing salt body from all the natural sand in the clay ... for alas, I won't go through that again and your clay being a higher iron content will be different formulation.

Now, that isn't to say, that your clay you dig isn't going to be an awesome slip/glaze or even a glaze ingredient at higher temps so I would also keep that in mind before trying to use it like redart in a clay body.

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And marcia is spot on with the silica ... go with 200 mesh since it doesn't need to be all that refined in a body unless you want pristine clay bodies like porcelain.

#4 Biglou13

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Posted 06 May 2013 - 12:57 PM

When I lived in Florida, I used to dig my own clay ... wonderous stuff too, had lots of sand in it so it was great for throwing and while it was white-ish it turned to a red-ish clay after and was only earthenware clay at best ... but I used it for pit firings so i never needed to worry about the sand or going higher. The few times I did use it for something else, i was meticulous in making it useful in a clay body ... my recipe was:

25% dug clay
25% fire clay
25% epk
20% flint
5% fine grog.

In order to do this recipe, I needed to dig the clay, dry it out, powder it to small pieces, slake to siftable consistancy, sift to 100 mesh (filtered larger sand and other large debris out) ... really not worth it since the time to do this was agonizing and it costs less just to buy ball clay ... but in an area without as much sand or rocks the lake clay will be much easier to prepare for consistant results. In the end I got the clay up to cone 10 and it was pinkish in ox, rustic brown/grey in high fire, but was my go-to for iron bearing salt body from all the natural sand in the clay ... for alas, I won't go through that again and your clay being a higher iron content will be different formulation.

Now, that isn't to say, that your clay you dig isn't going to be an awesome slip/glaze or even a glaze ingredient at higher temps so I would also keep that in mind before trying to use it like redart in a clay body.

-------------------

And marcia is spot on with the silica ... go with 200 mesh since it doesn't need to be all that refined in a body unless you want pristine clay bodies like porcelain.


AA, Where in Florida. I'm in north fla and am interested in making my own locally grown clay, what do you look for, wherr, so any info is appreciated any pics of the clay finished?
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#5 AtomicAxe

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Posted 06 May 2013 - 03:20 PM

AA, Where in Florida. I'm in north fla and am interested in making my own locally grown clay, what do you look for, wherr, so any info is appreciated any pics of the clay finished?


Couple places, but more towards the marsh land areas around sarasota, fort myers and up around tampa. Best place I found for clay like this was in my home town in of Lehigh Acres .... about 4 foot down is a solid 3 foot layer of clay between spots they dug canals to make sure fort myers doesn't flood when it rains in Lehigh.

Interesting note, when lehigh (7 feet above sea level) had hundreds of canals dug ... they used that dirt/clay when a gas station gets decommissioned ... they dig out all the dirt from 2 to 6 feet below the water level and fill it in with new dirt then incinerate the old dirt ... cool fact. ... also shows how anal retentive Florida is about it's ground water getting polluted.

North florida, might just want to pop up to the GA mountains and dig some red clay. ... you may find some of the clay that is above the lime stone layer like in central to south florida ... but I doubt it.




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