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BlackDogPottery

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 Lawn.)

D.M.Ernst likes this

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