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Veggie Clay


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#1 spam

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Posted 17 October 2013 - 05:49 AM

Has anyone ever heard of veggie clay or experimented with different vegetables and organic material to gain different colours?

 

 



#2 Chris Campbell

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Posted 17 October 2013 - 10:49 AM

That's kind of what Mother Nature did when the clay was created!
I have heard of people adding various organic things for surface texture and the pit firing crew definitely add all manner of organics to their surfaces for color ... But I have never heard of anyone adding these things to their working clay in order to get colors. You would have to use it fairly quickly due to rot and smell ... Then you would have to deal with its texture. Might be interesting to play with this idea though a good chemistry background would save a lot of time.

Chris Campbell
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#3 PeterH

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Posted 17 October 2013 - 11:56 AM

spam,

 

Could you elaborate on your thinking a little. It's hard to see how vegetable or organic material could

survive at anything like normal firing temperatures. Which is not to say that some of the inorganic

chemicals in the residual ash could not influence things a little.

 

There is always paper-clay of course, where the fibres give strength to the unfired article, but then

burn-out completely.

 

At the much more modest temperature of 150-200C the Mayans managed to combine indigo and the

mineral palygorskite to produce Mayan Blue. Which is remarkably resistant to fading over millennia --

and to attack by acid or alkali. Considering the normal fugitive nature of indigo pigments this is an

astounding achievement.  See for example:

http://archaeology.a...t/maya_blue.htm

... although the fine details are AFAIK still the subject of research.

 

Regards, Peter



#4 spam

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Posted 21 October 2013 - 04:23 AM

Thank you both for responding

 

Yes it is Chris :D My thoughts exactly.  One of my students came to me excitedly telling me about how you can make veggy clay, that you can get colour from bananas!  I thought perhaps they had confused ash glazes with clay but I have been working fairly isolated for the last 20 years and thought a more recent graduate on the forum may have experimented with organic residue.  I am a bit out of touch. 

 

Many thanks Sam



#5 perkolator

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Posted 21 October 2013 - 02:38 PM

bananas are a bit different since they are so high in potassium content (as will be any organic thing with high mineral content).  when you fire a banana sitting on top of a slab of clay to say ^6, there is enough mineral content in the residual ash that you will have a "fumed" silhouette where the banana was sitting.  this is because potassium is a flux.  i'm not exactly sure where your student got the idea of "color" coming from the bananas, but if it's a reference to the fluxed out section then yes - i'd consider it like raw clay vs clay with a little more flux inside or wash over it.

 

my student get to do a test firing of whatever they want on slabs of clay, I've yet to see one that actually makes a significant change in "color".  some do have great effects, like bananas (and I think it was cheeto's), but most organic items simply burn out all the carbon.  some great things to test this way are toothpaste, tums, dog food, "boosted" foods with extra mineral content, etc.



#6 Nancy S.

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Posted 21 October 2013 - 02:52 PM

So, wait, do you put the banana peel on top of the glaze? Or do you fire it on the bisqued clay, and then refire with a glaze? Or do you put the banana peel on the greenware, bisque, and when you fire to ^6 with the glaze the "fuming" still remains?

 

Now I really want to try "bananaware"....



#7 perkolator

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Posted 22 October 2013 - 03:52 PM

it's seldom that I bisque-fire work unless it is thin, wheelthrown functional wares.  for the "bananaware" all I do is sit a banana (don't know if ripeness effects it) on a slab of clay (either fired or green) and then fire it up to ^6 - it's that simple and can make a beautiful tile piece all by itself.  

 

when we do this with students, we require them to make a low-walled tray (slab with maybe 1/2" high wall on border) and fire their test objects in that since we don't know how many of the things they put in the kiln will melt/react in unpredictable ways.  we only do this in the gas kiln due to the burnoff - i suppose it could be done in a well ventilated electric, but i'd assume you will get deposits on bricks and elements that will lessen their lifespan.  many times the students don't think outside of the box when it comes to random things to test fire in a kiln, and they usually fire simple things that don't do anything -- but i've seen some pretty bizarre results from some of the junk foods and candy out there these days.  sometimes you get weird results from cosmetic products like soaps, lotions, shampoos, etc depending on what's in the ingredient list.  it's a really fun thing to do if you have the ability.






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