flascbryan Posted December 20, 2012 Report Share Posted December 20, 2012 Hi, everyone, can you all help me, I am brand knew at all of this ( Never made anything). But I am trying to determine how to use local clay here in south carolina. I have of course red clay and a creek bottom gray clay. How do I determine if any of these are usable? I have 4 -5 gallon bucket samples I am in the process of cleaning, have samples in jars to look at the sand vs. clay content ( not sure what it should be) Also have a mini kiln from 1950's that I can heat clay and test. But need to know best way to determine what clay is best and what is a waste of time. Link to comment Share on other sites More sharing options...
Chris Campbell Posted December 20, 2012 Report Share Posted December 20, 2012 Well, like the early potters it will come down to testing, modifying, mixing and more testing ... But if they could do it so can you! What they did not have was Google ... There are a lot of potters working with local clays and I would begin my search online so you could read their blogs and their articles. Good luck and hope you have a fun journey ... remember that all clays are local clays for someone. Link to comment Share on other sites More sharing options...
Marcia Selsor Posted December 21, 2012 Report Share Posted December 21, 2012 Hi Flascbryan, I tested a lot of clays in Montana many years ago. My method was: to slake the clay, pour it through a screen (window screen was ok, dry it out on plaster or in plaster vats, make shrinkage tests of 10 cm., as well and plasticity tests of twisted coils, then fire them on stoneware tiles first to a low temperature. If they looked like pinkish bisque, I would fire them higher. Many were decent earthenware clays which I used for "primitive pottery" classes and fired in pits with cow manure. Marcia Link to comment Share on other sites More sharing options...
TJR Posted December 21, 2012 Report Share Posted December 21, 2012 The thing you have to be careful of, is your clay melting and running all over your nice little kiln. As Marcia suggested,place your clay samples on tiles. You could also make some clay dishes with low sides, from a clay body that you purchased and know will take the temperature. I would suggest firing at a bisque temperature of cone 06[ not 6!] In my area of Manitoba, we were at the bottom of a huge glacial lake called Lake Aggassi. All of our clays have microscopic sea creatures in them that lower the melting point of the clay. We can only use our clays for slips, and slip glazes. But remember, all clays are useable for something! Good luck. TJR. Link to comment Share on other sites More sharing options...
OffCenter Posted December 21, 2012 Report Share Posted December 21, 2012 Also, after doing what is suggested above (mainly testing, testing and more testing), if you do come up with a clay you want to use for functional pottery be sure to test for leakage. It should not leak when you leave an unglazed cylinder full of water on a piece of paper overnight. Don't depend on glaze to stop a clay from leaking. I hope you discover a fantastic clay. Jim Link to comment Share on other sites More sharing options...
weeble Posted December 24, 2012 Report Share Posted December 24, 2012 Playing with native clay is a lot of fun, I had students in a class (all adults) do it one semester to mix things up from our handbuilding with commercial clay. We processed the clay by the standard dry it, break it up, sift out the big stuff, slake it, check for texture, then dry until usable and wedge. Everyone had to do their own sample, so we had 4 or 5 different clays by the time we were done (several of us had very similar samples, others were very different. When we got our samples wedged and made sampe tiles up, we fired in trays built from commercial clay to test quality, shrinkage, and workability. Our final results (for Oregon coast clays) showed most of our samples fired very nicely up to cone 5, with slight variations in color. Sand had to be removed in a few cases, but most started greenish-gray to orange but fired a very nice brick red. One sample (from the riverbed) was dark brown and heavy in organics, and fired pretty close to completely at cone 05. At cone 5, that one was a nice brown color, but bloated and slumped over, way overfired. We're plotting to try turning that one into a glaze one of these days. The moral of the story is testing is essential. Your local potters who use local clay can probably give you better ideas than most of us here as to what you will get, but even then you might get some surprises so be prepared for the worst case scenario. The problem is, the processing is time consuming and messy. Your best bet would be learn how a good commercial clay behaves and is used before you wander off to rediscover the process. Find a local club or art organization with pottery, someone there will be able to help you get a feel for clay, how good clay feels and how it SHOULD react to heat to be practical vs decorative. Most of all be prepared to have to work a bit to get that raw muck into the form of useful clay. You may luck out and have clay usable right out of the ground, but chances are it'll challenge you. Link to comment Share on other sites More sharing options...
TJR Posted December 24, 2012 Report Share Posted December 24, 2012 Playing with native clay is a lot of fun, I had students in a class (all adults) do it one semester to mix things up from our handbuilding with commercial clay. We processed the clay by the standard dry it, break it up, sift out the big stuff, slake it, check for texture, then dry until usable and wedge. Everyone had to do their own sample, so we had 4 or 5 different clays by the time we were done (several of us had very similar samples, others were very different. When we got our samples wedged and made sampe tiles up, we fired in trays built from commercial clay to test quality, shrinkage, and workability. Our final results (for Oregon coast clays) showed most of our samples fired very nicely up to cone 5, with slight variations in color. Sand had to be removed in a few cases, but most started greenish-gray to orange but fired a very nice brick red. One sample (from the riverbed) was dark brown and heavy in organics, and fired pretty close to completely at cone 05. At cone 5, that one was a nice brown color, but bloated and slumped over, way overfired. We're plotting to try turning that one into a glaze one of these days. The moral of the story is testing is essential. Your local potters who use local clay can probably give you better ideas than most of us here as to what you will get, but even then you might get some surprises so be prepared for the worst case scenario. The problem is, the processing is time consuming and messy. Your best bet would be learn how a good commercial clay behaves and is used before you wander off to rediscover the process. Find a local club or art organization with pottery, someone there will be able to help you get a feel for clay, how good clay feels and how it SHOULD react to heat to be practical vs decorative. Most of all be prepared to have to work a bit to get that raw muck into the form of useful clay. You may luck out and have clay usable right out of the ground, but chances are it'll challenge you. Weeble; I wouldn't pass up your bloating river bottom clay. Obviously, it would make a great slip glaze, or as a substitute for Albany slip. You can also add one-two percent to a clear glaze instead of iron to make a nice Celadon. The mantra here, as always, is test,test,test. TJR. Link to comment Share on other sites More sharing options...
weeble Posted December 26, 2012 Report Share Posted December 26, 2012 Yep, we've kept the sample around, and as time allows we try new things with it. So far it works very nicely for a decorating slip. Link to comment Share on other sites More sharing options...
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