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Food Safe Cone 6 (5) Ox Glazes Please


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#1 Biglou13

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Posted 26 February 2014 - 10:02 PM

I sort of have a customer. Sort of a first commission.....
It's more so trade pottery for food, it's bakery (European style organic sourdough starter thick crust kinda bread)
Thing is only one of my glazes in my "pallete" is food safe and not crazed.
I'm sort of picky(limited) in what I like creatively and what works for me.
My pallete now includes a black (hairs fur ish) (food safe), Bob which is a oribe (ish) green, And the many effects from one shino (ish) glazes.

And when they mentioned trade for bread for life or something like that. First I was flattered then I thought to myself, you know how much good bread, I can eat. (I'm a big guy). Well sounds like a goo deal all around the even offered me a shelf to sell my ware at bakery.........

Fast forward I need a few more food safe glazes........

I make test glazes tomorrow

Maybe this will give you some direction what interests me.

Tomorrow ill be making
Celadon (ish)
Randy red
A few albany based , Rutile and brown jug
Tenmoku(ish)

These have been tested in other studios as food safe and I like the colors.

I'll also finish tweaking shino (ish) glaze so not to craze.

Any suggestions and recipes would be greatly appreciated .

Pictures or links would be greatly appreciated.
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#2 Pres

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Posted 26 February 2014 - 10:17 PM

Have you seen this article in the Ceramic Arts Daily?

 

Recoloring a Classic: Trying New Colorants in a Classic Pottery Glaze Recipe Can Lead to Some Great Results

 

http://ceramicartsda...-great-results/


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#3 Tyler Miller

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Posted 27 February 2014 - 12:10 AM

A solid clear glaze and some engobes/underglazes could be a useful thing to have in your repertoire.  It would open your colour palette back up, maybe.

 

I haven't personally tested a clear glaze recipe I can recommend for ^6 oxidation, but there are many to be found here, I think.



#4 Marcia Selsor

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Posted 27 February 2014 - 08:15 AM

Here is the green from my gallery section on Forum discussions. There are some more there as well.recipes may be under the comments.

http://community.cer...-green-6-plate/

#5 JBaymore

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Posted 27 February 2014 - 10:31 AM

Lou,

 

Watch oribe-type copper glazes for (Western Style) interior container surface food use........ copper is notoriously difficult to "hold" in a glaze.  When the percentages get up there to get beautiful Oribe-stlye greens....... they can start to leach copper.  If there is any black flecking in the color... that almost for sure will leach.

 

The tiny percentages in copper reds are not an issue.

 

Copper is not greatly toxic, but it changes the taste of food if it leaches. 

 

However, for the tiny fraction of the population with Wilson's Disease, it can seriously affect them.

 

best,

 

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


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#6 JBaymore

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Posted 27 February 2014 - 10:34 AM

Lou,

 

Your PM mailbox is full. :)

 

best,

 

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


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#7 Pres

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Posted 27 February 2014 - 10:59 AM

John, is 2% Copper Carbonate in an "Oribe" a problem if fired correctly?


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#8 JBaymore

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Posted 27 February 2014 - 11:08 AM

John, is 2% Copper Carbonate in an "Oribe" a problem if fired correctly?

 

Most likely not.

 

best,

 

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


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#9 Pres

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Posted 27 February 2014 - 11:18 AM

Thanks, I was intending to test this Oribe recipe when I got back into the shop as it looked like it would work well on the darker body I am using of late.


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#10 JBaymore

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Posted 27 February 2014 - 12:53 PM

If you are talking about the glaze with 2% copper from the link above......... I just ran it in Insight.  Whikle it is within limits in most cases (looked at multiple limit formulas) the silica number is at the bottom end of the range.  So that says that the glaze might not be as durable as one could want in that cone endpoint range.  Worth some testing, for sure.

 

best,

 

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


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#11 Biglou13

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Posted 27 February 2014 - 07:25 PM

Lou,
 
Your PM mailbox is full. :)
 
best,
 
..............john


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Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#12 ChenowethArts

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Posted 27 February 2014 - 08:23 PM

I mixed up a batch of this clear Cone 6 from a Michael Sherril workshop to use over textured and RIO pieces and had good success when sprayed on...but these were decorative pieces, not functional wares.. It would be nice to get a confirmation that this is indeed food safe:

Ferro Frit 3124 -- 32.2%
Feldspar (Soda F4) -- 25.8%
Silica -- 19.4%
Whiting -- 12.9%
Kaolin EPK -- 9.6%
Total -- 99.9%


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#13 JBaymore

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Posted 27 February 2014 - 08:44 PM

In order for a glaze to have issues with leaching relative to the questions of food safety, there has to be something in the glaze that is potentialy toxic.  Just looking at that recipe as it sits, if you know your raw materials oxide sourcings, there is nothing there that is particularly harmful.  So that is a good starting point. 

 

However.... add a potentially toxic colorant... and that potentially changes things.

 

This says nothing about visual durability as to dishwashers, knife marking, and so on.

 

best,

 

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


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#14 JBaymore

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Posted 27 February 2014 - 08:54 PM

Just ran it in Insight.  It is a bit oversupplied with CaO (which weill tend to cause it to react with underlying clay bodies and will cause it to tend get micro-crystaline percipitation on the surface in slow cooling situations), but other than that..... is solidly within multiple different limit tables.  Should be a reasonably stable cone 6 glaze as it sits.   

 

But the ONLY sure waty to know is lab testing.  If you add colorants........ that is the definitive answer.

 

PS:  The "lemon test" getting recommended all over the place is a 'rule out' test not a 'rule in' test.  Meaning if it fails the lemon test, it is not worth doing lab testing... it is unstable.  BUT if it passes the lemon test it is NOT necessarily going to "pass" an actual acetic acid lab test. 

 

best,

 

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


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Professor of Ceramics; New Hampshire Insitute of Art

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#15 Venicemud

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Posted 28 February 2014 - 06:38 PM

The glazes resulting from "Recoloring a Classic..." from Ceramic Arts Daily brush on beautifully, so one can splurge and make up several small batches and have enough to brush glaze quite a few pots.  I made up 500g batches and am considering more.



#16 Biglou13

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Posted 01 March 2014 - 09:21 PM

Re : falls,creek shino (ish)

Ok I'm sold !!

I adding this/these to tests this Wednesday

Are you portion calcifying albany/alberta slip to cone 022. Per alberta slip.com?
Or just raw alberta/slip?
Anyone test with arroyo slip?
Anyone test with lithium substitutes?
Anyone test with spodumene?
If not any drying cracking issues?

Anyone run tests on porcelain/porcelain(ish) bodies.....crazing issues?
Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
-Albert Einstein

#17 clay lover

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Posted 02 March 2014 - 09:16 AM

Paul, what sort of finish does your clear have, satin or glossy?



#18 ChenowethArts

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Posted 02 March 2014 - 04:53 PM

Paul, what sort of finish does your clear have, satin or glossy?

 

Thin spray coat is satin. Anything above that thickness is glossy.

-Paul


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#19 clay lover

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Posted 02 March 2014 - 05:30 PM

Paul, is a thin coat smooth to the touch and still satin?  I can get satin but rough and unfinished looking from my clear satin, but thicker, it gets milky, cloudy.



#20 Venicemud

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Posted 03 March 2014 - 10:43 PM

Re Fall's Creek Shino(ish)

 

I have had no problems with drying and cracking, and I do not prefire any of the Alberta slip.  The only other slip I have tried is Albany and had no problems there, but it is so precious that I switched to Alberta.  I have tried several clays but the closest I have come to porcelain is Laguna''s cone 5 B mix - worked fine.  Overall I think that of the colors (Mason stains and oxides) I have tried I prefer the glazes when they are on clays containing some iron - but that's probably just personal preference.  It seems to me that brown clays accentuate the shino(ish) quality.






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