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Ethics Of Selling Repaired Raku Forms


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#21 Kohaku

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Posted 22 October 2013 - 08:07 PM

 

 

Well, have you looked into improving your clay body strength or adding materials that make it more raku-friendly? I know you have probably thought a lot about this already, but a friendlier clay body could open new vistas.

 

I have... in that I've tried a range of pre-made clay bodies. What I haven't done is tried a re-formulated clay body. For example, Cass (in another thread) recommended adding 3-5% kyanite. I may ask my local supplier to try this. Other suggestions would be welcome.

 

 

 

Have you tried Piepenburg Raku clay? It contains kyanite but I imagine most raku claybodies would..Maybe Cass meant an additional amount of kyanite above what is already in it? It has been years since I have done raku but you mentioned in another thread that you think the cracking occurs either in the kiln or in the reduction chamber. Would it be possible to fire the glazes to maturity then let the piece cool in the kiln to about 900 or thereabouts, then remove it when it is still hot enough to ignite the combustibles but not at top temp?  Maybe avoiding the quartz inversion temp at about 1000F would help, just a thought.

Min

 

 

Thanks for the thoughts Min.

 

I've used Pipenburg- and I definitely see a reduced fracture rate. The problem is that pipenburg (like a number of the specifically formulated 'Raku' clays) is full of grog. For the surface carving that I do, the grog yields a ragged line, or grabs the carving tool and throws it off-course.

 

The second idea is interesting... but a number of the most interested surface effects seem to take place at higher temperatures than 900 degrees, and I'd hate to lose the organic character of the surface.

 

I've thought about firing in a sagger and then adding combustibles in-situ (eliminating the rapid cooling that happens when you move your wares from kiln to can. Not entirely sure how to do this safely though.

 

I'll be trying kyanite as an additive this weekend.


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#22 Biglou13

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Posted 22 October 2013 - 09:28 PM

Have you tried a very very fine grog
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#23 Chris Campbell

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Posted 22 October 2013 - 09:33 PM

I hope Marcia drops in here ... She is the alternative firing expert!
I am perplexed by your breakage ... What percentage of your work is cracking severely?

 

I just had a thought ... how deep is your carving? Is it deep enough to be giving the work different thicknesses ... does it give the piece week points where the stress affects it more??


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#24 Kohaku

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Posted 22 October 2013 - 10:20 PM

I hope Marcia drops in here ... She is the alternative firing expert!
I am perplexed by your breakage ... What percentage of your work is cracking severely?

 

I just had a thought ... how deep is your carving? Is it deep enough to be giving the work different thicknesses ... does it give the piece week points where the stress affects it more??

 

Chris- most of my stuff fires fine. There's one specific form that I make for fountains, however, that's been driving me crazy. Basically a ceramic mill wheel. See below. There was already some discussion on this thread as to why this form breaks so much. (Asymetrical cooling the most likelty culprit).

 

Other complex objects (lanterns in particular) have never cracked... with the exception of really large objects (e.g. drums over 16 inches in height, oversize tiles and platters).

 

I should probably just give up on this one form as a bad prospect... but I'm stubborn.

 

Twa_zpsd851f11f.jpg


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#25 Marcia Selsor

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Posted 23 October 2013 - 05:54 AM

Unless you are mixing your clay from scratch, adding kyanite would not be evenly distributed.
Can you tell us what else you are doing? How you prepare? Do you wait a day after glazing.
Are you dunking the pieces in water?
Peipenburg's clay is good.What clay are you using?
You can get raku clay with fine grog so that it is smooth.
Give us more detail about your procedures and your clay body.

Marcia

#26 Kohaku

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Posted 23 October 2013 - 11:22 AM

Unless you are mixing your clay from scratch, adding kyanite would not be evenly distributed.
Can you tell us what else you are doing? How you prepare? Do you wait a day after glazing.
Are you dunking the pieces in water?
Peipenburg's clay is good.What clay are you using?
You can get raku clay with fine grog so that it is smooth.
Give us more detail about your procedures and your clay body.

Marcia

 

I planned to mix the kyanite it using the slap and cut method (40 rounds). My impression was that this did a pretty good job of mixing- let me know if I'm wrong.

 

In terms of clays- SPS (where I shop) has several Raku clays, but all have a significant grog component. On their recommendation, I've tried both Alpine white and Sea Mix with sand.

 

I also use Helmer Kaolin (mixed and sold by local Wendt Pottery). I've detected no real difference between fracture rates across these different clays, and Helmer is by far the nicest in terms of throwing.

 

I'd be delighted to try a commercial Raku clay with a finer grog if you have any recommendations... although shipping could be a deterrent (I have family in the Seattle area, so SPS is a convenient stop).

 

In terms of prep, I always pre-glaze at least a day before firing. For delicate pieces, I do a very slow gradient on the temperature.

 

I do not dunk my work- although (glaze dependent) I do 'burp' the can. I use kevlar gloves for transfering delicate pieces (no tongs).


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#27 Min

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Posted 23 October 2013 - 10:23 PM

Plainsman Clay makes a Raku body that uses fairly fine mullite grog, not the usual firebrick or fireclay grog. A link to the info on it is here: http://plainsmanclay...data/RAKU97.HTM  There is a sieve analysis at the bottom of the page. Plainsman is very good about answering questions and technical support, Tony Hansen of Digital Fire is involved with their clay composition and testing.  



#28 Marcia Selsor

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Posted 24 October 2013 - 07:27 AM

Have you tried using paper clay?
It fires well in Raku.I had a ton special mixed by Seattle Pottery Supply. Maybe they would special mix Peipenburg with fine grog for you.

Marcia

#29 Kohaku

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Posted 24 October 2013 - 02:17 PM

Marcia... I've made some of my own paper clay for doing repairs... but my impression was that it didn't throw well. It's something I've been meaning to experiment with more.

 

It's probably worth talking to SPS... although I've often found my interactions with them to be a bit... 'special'. (Whole separate topic there).

 

Min- thanks for the tip on Plainsman's clay. I wish there was a distributor a bit closer than Helena... but I do need an excuse to visit the Archie Bray facilities.

 

I just wedged a round of kyanite into some clay this AM, and I'll be forging ahead with a few experiements...


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#30 Babs

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Posted 27 October 2013 - 02:05 AM

Were you happy with it?... wabi sabi?



#31 JBaymore

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Posted 27 October 2013 - 02:10 PM

A very wise woman once said:

 

Here is a question for you that might be your answer.

Think of a potter whose work you admire and whom you respect a lot.
Picture someone showing him the piece above as an example of the quality of work you make.

How would you feel?
Every piece of work you put out in the world carries your name and makes your reputation.

If you put that much time and energy into the carving STOP raku-ing them ... Get yourself a more predictable firing process.
All the raku special effects get nuked in the sunshine anyhow and it's not hard to simulate black raku crackle post firing.
My advice is to stop throwing away all the time and energy you put into surface decoration.

 

best,

 

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


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#32 Idaho Potter

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Posted 12 November 2013 - 04:09 PM

Kohaku,

 

I use Coleman raku (firing range 06 to 10) and it is fine grained. (It's from Clay Art Center)  It also is endurable during the kiln to smoke pot,   I don't do much by way of carving, but think this would work well if you are sticking to raku firing.  Your work is so beautiful, I'm kind of with Chris--try another firing technique.  If it's the luster quality in raku that attracts you, a second firing and you can have your lusters on a well vitrified clay.  B-mix without grog is smooth as butter and carves very well.

 

Shirley



#33 Kohaku

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Posted 12 November 2013 - 08:24 PM

Kohaku,

 

I use Coleman raku (firing range 06 to 10) and it is fine grained. (It's from Clay Art Center)  It also is endurable during the kiln to smoke pot,   I don't do much by way of carving, but think this would work well if you are sticking to raku firing.  Your work is so beautiful, I'm kind of with Chris--try another firing technique.  If it's the luster quality in raku that attracts you, a second firing and you can have your lusters on a well vitrified clay.  B-mix without grog is smooth as butter and carves very well.

 

Shirley

 

Thanks a ton Shirley- I'll check that out.

 

I'm not opposed to alternate techniques, but I'm pretty obsessed with the mosaic effect you get when carved lines are blackened. I suppose I could get this with India ink, but that seems a bit forced to me. Suggestions are welcome... but my experiments with sagger firing aren't promising (you can get a beautiful surface... but darkening the bare areas is more problematic)

 

I also love the organic feel you get with a Raku surface... not just the luster, but the variegated color, the crackle, and the textural residue of the combustibles.

 

Honestly, I feel like there's a lifetime of possibility for me to explore... and I'd rather explore form until I figure out which shapes can handle the stress and which can't.

 

David


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