raku chawan food safe ?


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raku chawan food safe ?

Postby matchamatchaman » Jun 14th, '09, 05:37

anybody using american raku chawan ?

i heard from a potter friend that american raku chawan are not food safe, is this true ?

i just bought a pagasari chawan

thanks
M
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Postby MarshalN » Jun 14th, '09, 09:26

Traditional Raku has lead in it, so if you're worried about lead content in any miniscule amount, no, it's not food safe. In Japan they made an exception for raku-ware, I believe, the reasoning being that for each bowl of matcha made the tea is only sitting in the bowl for a very short period of time, or some such, and the amount of lead isn't huge, so you're really not in much danger at all. Just don't give it to kids I guess.

Don't know about American raku ware.
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Postby chicagopotter » Jun 14th, '09, 09:42

I think one of the other concerns about American raku is that the clay body tends to remain extremely porous. Because raku firing happens at such a low temp, the body does not vitrify and the glazes used do not seal the surface. This can lead to bacteria breeding in places where it shouldn't. American raku also takes the process one step further by placing the red hot piece in a post firing reduction atmosphere which causes smoke/carbon to color cracks in the glaze and darken the clay body.

Regarding the lead content of the glazes, you should contact pagasari for more info. His Etsy, eBay, and main website have no info about the glazes.

However, thinking about this now and the difference between Japanese Raku (no post firing reduction) and American Raku, I wonder if food safety is a construct of our society? As MarshalN states regarding lead content, I wonder if it is also true for porosity of the clay body? "In Japan they made an exception for raku-ware, I believe, the reasoning being that for each bowl of matcha made the tea is only sitting in the bowl for a very short period of time..."

Guess it all comes down to your own personal feelings on the like.
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Postby xuancheng » Jun 14th, '09, 11:58

I think another issue with raku-ware Is that food with vinegar will damage the glaze. Maybe it just leaches lead more than tea, but my understanding is that it can actually damage the piece.

I guess I wasn't sure if you meant food-safe for tea, or for other things. Don't use them as salad bowls!
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Postby chamekke » Jun 14th, '09, 13:19

This issue has been discussed exhaustively on these older threads:

Raku Lead Glaze Concern
Safety, Lead in TeaWare Glazes

I personally do not take any chances with American Raku. In my household, it's purely for display.
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Postby chicagopotter » Jun 14th, '09, 17:59

chamekke wrote:I personally do not take any chances with American Raku. In my household, it's purely for display.


I totally agree...
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Postby coloradopu » Jun 14th, '09, 20:00

that show-e stuff on the shelf shore is pretty but give me a good stoneware piece any day.
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Postby Seeker » Jun 15th, '09, 00:20

I'm very glad for this topic!
I recently acquired a Pagasari, and have been happily drinking matcha out of it.
Then, I received a note from an artisan I'm acquainted with that Raku aren't safe for using!!
The horror, the disappointment! :shock:
Well, I've been in contact with Pagasari and here is what he says (it's pretty choppy, but he's french and has to use the google translator):

>>To answer your questions, I never used to plom in glazes that I make myself. I use my bowls every day and I am very careful to my health. You can use all kinds of liquids except the vinegar (sometimes there are people who put in the salad bowls tea is weird I know ...) which destroys the structure of the glaze. For everything else there is no problem.

In the raku sometimes the earth is sometimes seeming to leave the apparent carbone but it's something that I do not use in my pieces. I realize thermal shock without plunging the room but the smoke just in water or snow, then I fill the cracks oxides for cracking black. I sometimes put to fire 10 to remove the earth and between each layer of color.

Then you should know that glazes that are fired at 1000 degrees are much more fragile than cooking at high temperatures because the earth is like a sponge that is not closed.

This is part of the charm of Rakus changing with time. Often it takes several months of use so that the true character of the piece appear, the whole magic of this type of object.

ps: sorry for my english I use google translator ^^<<

I think in that first sentence "plom" must be lead; I've sent him another note to clarify; also to make sure he only uses his own self-made glazes (which he doesn't use "plom" in, ever, he says);
I also, though, want to find out what other substances might leach (apparently, if it's Raku, it's gonna leach - holes/bubbles, cracks) - how about barium carbonate (Rob Fornell says that's nasty stuff).
I'll keep us all posted.
I continue to explore this potential problem.
I hope it turns out okay - I'd hate to never be able to safely use mine. :(
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Postby Tead Off » Jun 15th, '09, 01:26

plomb is lead in French.
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Postby xuancheng » Jun 15th, '09, 02:07

Tead Off wrote:plomb is lead in French.


And latin, and even English, too practically. A plumber is the word for a man who works with pipes because all pipes used to be lead.

wikipedia wrote:The "plumb" in "plumb-bob" comes from the fact that such tools were originally made of lead (Latin: plumbum). The adjective "plumb" developed by extension.
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raku chawan food safe ?

Postby bonjiri » Jun 15th, '09, 03:47

humbly

for me

as for utilitarian ceramics (ceramics u use)
i don't use any low fired raku ware.

seeing and knowing a little about the process, i usually only use high fired, lead free, barium-free and manganese-free ceramic ware.

*********one big issue is not only the lead but the fact that the clay is not vitrified, meaning if u put a liquid, like tea, the piece will absorb the liquid and leak. the clay is not vitrified.

cheers

c
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Postby Seeker » Jun 15th, '09, 04:26

An interesting note - mine totally does not leak or even get moist on the outside.

I'm going to contact paga and ask if he uses barium and/or manganese.

For now, I'm putting my pagasari up on the shelf.

Probably retiring it for good. :(

Oh well. Live and learn.
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Postby Tead Off » Jun 15th, '09, 07:36

Seeker wrote:An interesting note - mine totally does not leak or even get moist on the outside.

I'm going to contact paga and ask if he uses barium and/or manganese.

For now, I'm putting my pagasari up on the shelf.

Probably retiring it for good. :(

Oh well. Live and learn.


Maybe you could trade it back to him for some good Camembert? :wink:
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Postby Seeker » Jun 15th, '09, 14:24

Tead - Yes, great idea! :lol:

btw - here's his latest response to my query about whether he uses barium or manganese (already confirmed he doesn't use lead):
>>Greetings, to answer your questions, I do not use any of these products. (Barium, barium carbonate, or any kind of manganese in your glaze) You should know that the barium is handled with care, it powder is dangerous if you swallow and breathing, but once it was cooked with the glaze there is no issue of dangerousness in part to the person preparing the glaze, use a mask and gloves, that's all. For the components of my glazes, using a lead-free frit, with the porcelain powder and silica, kaolin. Oxides, only iron oxide red, black, cobalt, copper and a little tin. The colors are obtained with engobes made from natural pigments, I do not use artificial coloring. My recipes are very simple, but sometimes several components 3 glazes.<<

So I'm back to wondering if it's safe, knowing that what he does use will likely leach through the porousness of the piece (I'm don't know about cobalt for instance); And though I ONLY use my chawan for matcha, still, boiling water can cause leaching, at least I would think so - it most certainly does with plastics.
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Postby Seeker » Jun 16th, '09, 19:35

Just found out that pagasari does use copper in his glazes. Copper can leach when exposed to acidic environments.

I didn't know this, but a prominent ceramic artist (not associated with this site, though some wish it so) informed me upon inquiry that matcha is acidic, and that with raku there would then be concern if copper is used or (aluminum?... don't know if I'm remembering this one properly, the email with this info is on my desktop at home, and I'm on laptop at work). He also informed me that lead is often used in raku, and of course that poses health concerns, but pagasari doesn't use lead - so no concern there.

pagasari also uses tin in glazes, and I don't know about the health affects of tin being leached.

I think my pagasari is only for display now.
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