Bisque temp for raku

[eoteceramics]

Hi all,

Im very excited to be making a raku kiln, now I'm new to this method so will be firing some raku Q's at you all.

Be prepared for some daft ones!

• first up, Is there an ideal temperature to fire a stoneware clay to bisque if wanting to do a raku glaze firirng?
• Has anyone a glaze recipe for a beautiful blue or green, or is there a good resource for raku recipes somewhere?

Thats it for now, be warned I may be back!

Julia

 

 

[William K Turner]

You should never bisque for raku above cone 06.  I bisque to cone 09.

Raku Art Inc.

[Benzine]

3 minutes ago, William K Turner said:

You should never bisque for raku above cone 06.  I bisque to cone 09.

Raku Art Inc.

Really?  Why is that?

I usually go to 04 with mine, and have had no issue.  The reason I do so, is because I go to 04 for my main classroom clay, and it doesn't make much sense to do a separate firing for the few Raku projects we do. 

[Denice]

Why do you want to use a stoneware clay in a Raku firing?  Using a low fire clay will make your piece stronger,  stoneware will be extremely fragile at that temperature.   Denice

[Benzine]

Denise,  I have used stoneware, for Raku as well.  The school district, where I learned the process, fired to Cone 5, for most projects, prior to me starting there.  So it made sense, to use the same clay for  our Raku firings, if the same  clay body would work, which it did.  So I stuck with that same approach.  

The stoneware body worked well, the same reason that specific Raku bodies work, they are intentionally underfired.  This is what allows them to handle the thermal shock associated with the process. 

In a matured ceramic body, the particles are locked together, which is great when you are making functional wares, thay don't seep liquids,  but bad for something that has to tolerate quick/ dramatic temperature changes during the firing.  That locked ceramic structure is not good at quickly transfering energy from one part to the next. So the expanding and contracting that happens, leads to cracks/ dunting.  This is why you are not supposed to put a glass or ceramic casserole from the fridge into a hot oven.

With an underfired body, the bodies are still "open" and the particles are not fully locked together.  There is space between them, which allows the heating and cooling to be relatively gradual, and lessons the odds of dunting.

I have honestly never tried to use low fire with Raku, but I have taken low fire pieces, out of the kiln, when they were still somewhat hot(200 degrees F) and had them develop cracks.

Being weak due to underfiring, is the nature of Raku.  With the exception of the Japanese Tea Ceramony,  Rakuware, is not meant to be functional, so it's relative fragility is not that big of a drawback.

[LeeU]

Steven Branfman's Mastering Raku is a comprehensive wealth of information if you really want to get into it. He generally bisques at ^08 (explains in the book) and uses a commercial raku body...Sheffield has a nice one.

[eoteceramics]

On 5/11/2018 at 8:58 PM, Denice said:

Why do you want to use a stoneware clay in a Raku firing?  Using a low fire clay will make your piece stronger,  stoneware will be extremely fragile at that temperature.   Denice

Thanks Denice, first time doing this so learning fast. Im planning on adding silica sand to my earthenware clay , does that sound like the right thing to do?

[eoteceramics]

On 5/15/2018 at 3:17 AM, LeeU said:

Steven Branfman's Mastering Raku is a comprehensive wealth of information if you really want to get into it. He generally bisques at ^08 (explains in the book) and uses a commercial raku body...Sheffield has a nice one.

thank you I have his book and am making my way through it, very informative

 

[hitchmss]

On 5/13/2018 at 8:32 AM, Benzine said:

Denise,  I have used stoneware, for Raku as well.  The school district, where I learned the process, fired to Cone 5, for most projects, prior to me starting there.  So it made sense, to use the same clay for  our Raku firings, if the same  clay body would work, which it did.  So I stuck with that same approach.  

The stoneware body worked well, the same reason that specific Raku bodies work, they are intentionally underfired.  This is what allows them to handle the thermal shock associated with the process. 

In a matured ceramic body, the particles are locked together, which is great when you are making functional wares, thay don't seep liquids,  but bad for something that has to tolerate quick/ dramatic temperature changes during the firing.  That locked ceramic structure is not good at quickly transfering energy from one part to the next. So the expanding and contracting that happens, leads to cracks/ dunting.  This is why you are not supposed to put a glass or ceramic casserole from the fridge into a hot oven.

With an underfired body, the bodies are still "open" and the particles are not fully locked together.  There is space between them, which allows the heating and cooling to be relatively gradual, and lessons the odds of dunting.

I have honestly never tried to use low fire with Raku, but I have taken low fire pieces, out of the kiln, when they were still somewhat hot(200 degrees F) and had them develop cracks.

Being weak due to underfiring, is the nature of Raku.  With the exception of the Japanese Tea Ceramony,  Rakuware, is not meant to be functional, so it's relative fragility is not that big of a drawback.

Benzine; true a vitrified stoneware/porcelain will have a crystalline matrix which has developed inside the clay body at maturation, but most stonewares/porcelains mature/vitrify at least at mid range, or usually high fire temps. At a bisque ^04 a stoneware/raku clay would both be "underfired".

Raku clay is essentially a stoneware clay body with fluxes designed for proper melt at low fire temps lower amounts of flint, and added fillers to deal with thermal shock. Additions of fire clays, grogs, sands, pyrophillite, etc all help with this process. You can go through the hassle of wedging in materials into your clay, lots of hassle; a pugmill makes shorter and better work of this. If you're doing just a few pots then making your own is a good experience; if you're making a lot, just buy it. The hassle of mixing/dust isnt worth it.

   Typical bisque temps are anything between^ 08-04; at this point the clay will no longer slake back into mud if wetted, but still maintains porosity (keeps glazes stuck to the pots). I dont do a bunch of raku, so there may be some benefits for different "alternative" firing techniques similar to raku (horsehair, alcohol reduction, saggar, naked raku......), but in my experience I bisque at 04, glaze, and then glaze fire to ^04. If your process requires the glaze/surface to be fired to a lower temperature (08 instead of 04), then I would bisque to that lower temp as well.

[Denice]

The first raku I ever made was in 1968,  it was the newest and latest greatest event in ceramics.  You would use a rough groggy low fire clay and make a cup, glaze it immediately and fire it in the raku kiln.  After the firing everyone would sit around and drink hot tea from the mug they made.  Quite exciting.   My college professor pounded into our heads that the cone of the clay and the glaze should be the same.   He would get upset if a new student would use a different temperature clay and glaze together.  They wouldn't get a very good grade and he called it garbage because it wasn't vitrified.   Denice

[hitchmss]

3 hours ago, Denice said:

The first raku I ever made was in 1968,  it was the newest and latest greatest event in ceramics.  You would use a rough groggy low fire clay and make a cup, glaze it immediately and fire it in the raku kiln.  After the firing everyone would sit around and drink hot tea from the mug they made.  Quite exciting.   My college professor pounded into our heads that the cone of the clay and the glaze should be the same.   He would get upset if a new student would use a different temperature clay and glaze together.  They wouldn't get a very good grade and he called it garbage because it wasn't vitrified.   Denice

Denice, that info is contrary to everything I have ever been taught and experienced with raku wares. Are you saying you would glaze it immediately after making, as in, still plastic clay? How were you getting glazes to adhere to wet work?  I teach my students, tell my customers, and personally would never use any raku ware for utilitarian purposes, mainly because raku clay (in my experience) is never vitrified enough, and the glaze surfaces are not food safe. Not only are raku glazes designed for rapid heating/cooling (thermal shock), but they typically contain high percentages of oxides, which combined with the poor glaze chemistry, are way out of acceptable additions. Lastly, most raku glazes craze due to the thermal shock they undergo; combined with a porous clay body, there's just a timer set until the glaze/clay interface fails and becomes part of your digestive system.

Maybe I'm overly cautious and "preachy" when it comes to "raku pottery", but ever since I saw an inept (inept because she was told not to) beginner selling mugs through a coffee shop (with a clueless owner) and had to inform both of the law suits they were asking for, I make a point of informing.

 If Im wrong, Id love to know. Everything Ive been taught and learned contradicts though.

  

[oldlady]

hitch, i remember being in the same kind of firing as denise describes.  WHEN WE ARRIVED WE WERE HANDED SOME WET CLAY AND  WE MADE the pieces  by pinching, they were glazed with something the person firing the kiln gave us, they were placed around the edges of the converted electric kiln while it was heated up and then fired.    this was a L O N G  time ago when nobody knew better.

[Mark C.]

We always bisques at 08  0r 06 in the 70's then raku it. We made the glazed from some real nasty stuff (as well as safe) including white lead. Never used anything for functional wares-not drinking from cups rakued. Soon those materials where given up but in the early 70s at a state  collage  ceramics Dept they where very common.We made our own raku clay as well.Not many bodies available back then.

We all understood the not for drinking deal so no cups where made. I stall have those recipes. I took my personal 50# bag of white lead to a hazmat disposal 25 years ago.

Folks today get freaked out over what I call safe things like benign dry materials like feldspars -back then it was some real bad stuff but you knew it and handled it as such.

I kept raking at home  some for about a decade before moving on to strickley higher temp pots.I needed to make functional wares not art for a living.

[preeta]

Wow Denice and oldlady- you are describing true Japanese Raku, not the Americanised version it has become ( Mr Raku in Japan was so horrified  when he heard how Raku was practiced in the US, that he forbade using his name to the process. But unfortunately Paul Soldners happy accident of dropping red hot ware on leaves and seeing what it did had become too popular and common for its name to go away)  can you tell my profs have been Soldner’s students. 

Ive only heard and read about those parties, never met anyone who attended one. Wow that’s truly history!

So the American Raku (which really should not be called Raku at all - perhaps call it Solder would be right and he would love it)  methods are completely different.  The commercial Raku claybody we get on the west coast is a cone 10 claybody. 

In all 3 of my schools rakuware gets fired to cone 04 and they are fine.  Just like Benzene said. 

However I have noticed porcelain especially (cheap and expensive kind) is very fragile when thrown thin. It’s quite an art to handle those tongs without breaking thin porcelain pieces. 

 

[Sputty]

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[Benzine]

preeta, I always preface my student discussions about Raku, with how what we are going to do, is not the same, as they traditionally do in Japan.  As you noted, I call what we do "American Raku".  I usually mention, that as Americans, we try and "improve" things, with the addition of fire and explosions...

In regards to using Rakuware, yeah, I would never do so, and tell my students the same, explaining why.  I made a decorative Raku tea set, for my older sister years ago, and explained that they were not meant to be functional.  Then at a family gathering, she mentions, "I use them for my mac and cheese all the time!"  I responded, "Stop that!!!"  I find that funny, as I made her a functional casserole years before, and joked about the glazes not being safe, or coming off into the food, and she adamantly grilled me to find out if I was telling the truth.

When this topic came up, in the past, John Baymore would talk about how the Japanese would rigorously clean their Raku tea bowls, as part of the ceremony.  So any dangerous glaze materials, or bacterial/ mold growth, were likely washed away before use. 

Personally, I would not be afraid to use a Raku piece, of either American or Traditional firing, but I wouldn't do so every day.

 

And Mark, I can't believe you would just toss all that deliciously sweet tasting white lead!...

[Denice]

That white lead would have been great for some Majolica tiles.   Denice

[preeta]

Sputty honestly Japanese art philosophy is at such a different place that I don’t think any country can truly understand it. I mean if Warren McKenzie was walking down the street no one would utter in awed whisper there goes a famous potter, as they would a National Treasure in Japan. 

So I don’t expect the same reverence. 

I have no problem with cross cultural knowledge without the traditions carrying over. There was a great talk on tea bowls this year at NCECA on This very point that I watched on YouTube.  

But I get what you are saying esp when the name Raku is used. However those were the times and I really wish we had a different name so we can truly celebrate our type of Raku because it is so full of flair and adventure and a perfect example of happy accident and deserves to hold its own without its Japanese association.  

Raku is big here in CA. There are quite a few tables and booths here in the city at fairs selling all types of Raku.  

One question I get asked all the time even with begin students is ‘Is this foodsafe’? Though from the students it’s mostly about vitrification that they don’t understand quite yet. I get so frustrated when they ask me about wood fired and cone 10 ware.  I have given that talk so so often.  

[Sputty]

.

[preeta]

Sputty I am with you a hundred percent 

but

esp where ceramics is concerned it’s such a different world.  I mean for that matter was Japanese Raku an apppropriation from Korea I wonder.  Don’t know that much history to know the answer.  

I feel cultural appropriation becomes a problem when the foreign culture makes money or some kind of gain at the detriment of others.  Like Native American art and big corporations or even art for that matter (which I saw at the solar eclipse which was abhorrent).

case in point - the chawan.  Or teabowl or all the other names. Everyone making pottery makes tea bowls. It’s almost become a form in itself like a teapot. One does not do a tea ceremony or follow any of the cultural norms.  

I think that’s ok. While outside my ceramic group I have yet to see anyone use a teabowl yet the one board in my Pinterest that gets the most saves and follows is my chawan board. 

[Sputty]

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[Rae Reich]

On 5/18/2018 at 7:53 AM, Denice said:

That white lead would have been great for some Majolica tiles.   Denice

Until some "food stylist" decides to serve tomato and lemon slices on them :p

[Rae Reich]

On 5/19/2018 at 12:27 AM, Sputty said:

China, rather, if anywhere. The history given here is interesting - History-Birth of Raku Ware - and especially worth a look is the 'Raku Successive Generations' menu item.

Is a tea-bowl still a tea-bowl if it's not part of a tea ceremony? I'd argue that it isn't; the context of an object is as important to its definition as its form or superficial function.

But it's probably all hair-splitting!

Yes, I'd say your hairs are split to their finest! Isn't there a difference between being inspired by an aspect of a culture and stealing it? Especially in our field, where it truly is built upon the world knowledge of most other cultures. A tea bowl is a handle-less cup from which tea is drunk. A chawan is much more specific. Our terminology is both old and new, as are our techniques and equipment and science. I love being a potter today.

From the very nice history article link you posted:

"The tradition is not only to be maintained.
What is essential in the tradition is eternally 
evolving through eyes of the present.
What matters are those eyes that could perceive
the tradition from the present perspective, which
is a very proof of our existence."

[Sputty]

.
 

[Rae Reich]

"Eternally evolving" was cancelled? I didn't get that memo.