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Identifying Clay Body


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For a while now I've been using a Terra cotta in a few slips as well as mixing it in my clay body. This came from some advice I read about adding amounts of earthenware to stoneware temps for better vitrification/glaze effects. It worked fine for the most part, as this is just a clay I picked up at a hobby store but strangely enough this "Terra cotta" is labeled as air dry clay (as in modeling clay for school projects). Now I was expecting it to be your plain ol Terra cotta but I noticed it felt somewhat off at ^06.

It wasn't that rich orange you expect but more of a bisque. So I made a test piece and fired it to ^7 expecting a puddle of ceramic. Surprisingly it was still there, reacted well with glaze, and seems pretty vitrified on the surface. It came out a very deep brown.

  For some reason I thought real earthenware would bloat and melt at stoneware temps. Could this be a stoneware clay in disguise? I would switch over but at $1.00 a pound that is some very expensive stoneware..

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Lol, yes I was given a sample of some ‘terracotta’ like this once.  Fired perfectly to cone 10, no distortion, no bloating, with a lovely 1% porosity that more than a few porcelain bodies would envy...

We discussed this problem directly in a thread entitled “what is Terracotta, really?” Started on 24 November, 2015.  I would link it here but cant figure out how.  If you search the forums for terracotta I am sure you will find it.

one-size-fits-all clay is alive and well and easily procured from your nearest clay store...

 

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lol, again! 

As a beginning student assigned to do a "process piece" in which the work would demonstrate the process, I thought it would be fun to overfire a pile of extruded strands of white and red earthenware. The idea was premised on the belief that ^06 clay would surely melt together at higher temps. So my "process piece" was at least a learning experience. One wag in class brought in damp, roughly formed "turds" on a paper plate, explaining that he had fed his dog some porcelain and then followed him around to collect the "extrusions" (He later helped form the band Suburban Lawns.)

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