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LeeU

Raku Question

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Lee,    Do you mean cone 6 stoneware that has been bisqued to some lower cone?  Or do you mean cone 6 stoneware that has already been fired to cone 6?

I've seen people use bisque (to something like cone 09 to 04) cone 6 clays in American Raku.  They seem to work OK.

best,

..........................john

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Nope--I mean ^6 clay fired (unglazed) to ^6.  I single fire to ^5 or 6 so I don't want to fill & fire  a bisque load just to have one fairly small piece for this activity.  I am thinking it should be just fine for this limited purpose.  The demonstrator is supplying oxides and glaze we can use there.  

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Nope, Lee.  Cone 6 clay fired to cone six will probably have a 99.999%  chance to succumb to thermal shock, either on the way up or the way down.

If there is ANY chance for survival for this cone 6 work, it should be put into a totally cold kiln and heated with the first load.  And take it up a bit gently.  Then pulled, and QUICKLY put in a container with combustibles, and LEFT there til it is cool.  Absolutely NO quenching.

The body will not be like bisque..... meaning non porous.  That quality is what allows raku ware to deal with the stresses of rapid and uneven heating and cooling.   It is also what allows smoke to penetrate into the body and casuse the "black" stuff.

best,

...........................john

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14 hours ago, Tyler Miller said:

I should say that white stoneware doesn't work stellar for raku.  Porcelain (actual, proper porcelain--the no ball clay kind)will work, but white stoneware has never worked for me.

I think it may depend on the specific clay body. The only white ^6 stoneware I ever used was a "vessel 6" which we mixed ourselves when I taught in Billings. I don't think we fired it in raku but we did fire out ^6 stoneware that we mixed.

 

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Well, as they say, there is no easier softer way!! I decided the experience is well worth getting a small bag of raku clay and doing a bisque fire.  I think I knew about smoke/porosity in the back of my head, but glossed right over whole thermal shock process, which I also knew about, at least intellectually, and conveniently forgot, seeking that easier softer way LOL.  Any recommendations for a simple clay for a 1 or 1 piece raku demo session?  Also, can a raku clay body be used the same as a regular low fire body, in an electric firing with commercial low fire glazes (so I can use up the clay)?  Thanks all.

Update 9/25. Finally found my copy of Steven Branfman's wonderful book, Mastering Raku, which has all answers I need for this. I was positive I had included it in a batch of good ceramics books that I sold a few months ago, so I never even looked. Someone said something about falling in love with raku.  I'm already falling for the clay body! And am thrilled to learn that it can indeed be fired in an electric kiln, in a raku process. 

 

Edited by LeeU

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Raku clay does not mature at low temperature. That it why it works in raku. Typically it can go to ^6 or even ^9 but you need to test. It is not really a lowlier type of clay, it is a porous open body at raku temperature  to deal with the thermal shock. That is why groggy stoneware works.

 

Marcia

 

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Hi, Lee

I say throw/slab/whatever a whole kiln load.  Big and little, flat, round, tall and skinny, being mindful of needing to lift it at a distance with tongs (tho, if it's huge you can get help). Choose what to take at the last minute and then bring along a couple of spares.  

The rest of the clay probably won't be wasted. If you don't come away from the experience just desperate to find a way to do it again, I'll eat a bug. 

Rae

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Although the image of somebody eating a bug is quite tempting, I am fairly sure I won't have much opportunity to do this again anytime soon. It is just a small demo for members of a potters guild -we can bring 2 pieces-and I have limited access to further raku firings.  The smallest bag I could get was 25 lbs-and I make pretty small items! So I will make some "extra" pieces and hold on to them for a future opportunity, but will also use the  leftover  04-06 raku clay  in  my  next ^6 electric firing (thanks Marcia). Rae. I will be sure to notify you if bug-eating becomes a real possibility--I will want pics.

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