Jump to content


Photo

Food Safe Cone 6 (5) Ox Glazes Please


  • Please log in to reply
40 replies to this topic

#21 Biglou13

Biglou13

    Advanced beginner pottery, Advanced in other art

  • Members
  • PipPipPip
  • 933 posts
  • LocationNorth Florida

Posted 03 March 2014 - 10:50 PM

Venice ... Thanks I make some tommorow
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

#22 Roberta12

Roberta12

    Advanced Member

  • Members
  • PipPipPip
  • 128 posts
  • LocationColorado

Posted 03 March 2014 - 11:32 PM

re: Fall Creek shino(ish)  I have mixed up a number of batches of the FCSish with copper carb, cobalt carb, and mason stains.   I use 2% on copper and cobalt and 5% on Mason Stains.  I have even tried a 1% on the copper which was nice also.  Just a little lighter green.  I have used all of the versions of FCS ish on brown speckly clay and on bmix and porcelain.   I like this glaze on all of the clays. However, I spray it and I like it best on white clay.    The first pic is of two green shino-ish bowls  The 2nd pic is the underside of a green shino-ish bowl.   The 3rd one is with vivid blue Mason stain and the 4th one is FCS ish with yellow ochre.   Hope all attaches.

Attached Files



#23 Biglou13

Biglou13

    Advanced beginner pottery, Advanced in other art

  • Members
  • PipPipPip
  • 933 posts
  • LocationNorth Florida

Posted 04 March 2014 - 04:09 AM

How does fcs perform. With standard tiring schedule?
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

#24 Roberta12

Roberta12

    Advanced Member

  • Members
  • PipPipPip
  • 128 posts
  • LocationColorado

Posted 04 March 2014 - 09:18 AM

It seems to be a no fuss, no muss, sort of glaze.  That's all I have used with the fcs, is a standard firing schedule.   I forgot to include just the base recipe in the pictures, but it's a nice brownish.   It doesn't run or move, lighter application gives more of the brown tones in any of the colors.   I had one weird thing happen when I first started using it.   With the copper carb fcs.   The outer layer sort of rubbed off when the customer put cranberries in it.   After having run a lot of tests here at my home, I came to the conclusion it was a anomaly.  I have not had a problem with it since.   I have even layered up the colors.   blue over green is nice.  

 

Roberta



#25 JBaymore

JBaymore

    Moderator

  • Moderators
  • 2,886 posts
  • LocationWilton, NH USA

Posted 04 March 2014 - 10:23 AM

 I had one weird thing happen when I first started using it.   With the copper carb fcs.   The outer layer sort of rubbed off when the customer put cranberries in it.  

 

Cranbetrries..... seriously acidic.  Surface color or quality change.......... glaze instability???????

 

That would be a "red flag" for me.  I'd want to know for sure WHY I got that result. If it happens once... it can happen again.  And I'd want to know if it is happening more... I just don't KNOW about it.

 

Lithium carbonate is a problematic raw material.  It is slightly soluble.... and that can cause REAL problems.....becasue it can impact the clay/glaze interface layer in bad ways.  Plus it is molecularly light... so a deceptively small weight of material is adding a LOT of lithium oxide molecules in the melt.  Li2O has the lowest COE of all of the oxieds we use.  This can cause issues with both fit and glaze stability.

 

Home tests don't really suffice for answering the question....... "Does it unacceptably leach copper or other colorants?" or the slightly less important question, "Will it stand up to long term repeated food and serving use"? 

 

Here's a quite from Ron Roy about that glaze: 

 

"This is a tough problem, not because of the GB but because that much
lithium Carb can be big trouble - anything over 2% can cause dramatic fit
problems - like shivering and crazing on the same piece - I don't recommend
this kind of glaze on anything that could be used for food - think about it
- flakeing pieces of razor sharp glaze in food - in people!"

 

If you don't know who Ron is....... look him up.

 

best,

 

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


John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#26 Min

Min

    Advanced Member

  • Members
  • PipPipPip
  • 429 posts
  • LocationCanada

Posted 04 March 2014 - 11:07 AM

It seems to be a no fuss, no muss, sort of glaze.  That's all I have used with the fcs, is a standard firing schedule.   I forgot to include just the base recipe in the pictures, but it's a nice brownish.   It doesn't run or move, lighter application gives more of the brown tones in any of the colors.   I had one weird thing happen when I first started using it.   With the copper carb fcs.   The outer layer sort of rubbed off when the customer put cranberries in it.   After having run a lot of tests here at my home, I came to the conclusion it was a anomaly.  I have not had a problem with it since.   I have even layered up the colors.   blue over green is nice.  

 

Roberta

 

I ran the glaze through Insight, the silica level is below limits by a little, plus the alumina is within limits but on the low end. Lithium levels is over when using Leadless Traditional Limits,  Doesn't look like a  durable glaze when you look at the numbers. 

 

 

CaO 0.36*
Li2O 0.25*
MgO 0.20*
K2O 0.07*
Na2O 0.12*
P2O5 0.00*
TiO2 0.01
Al2O3 0.29
B2O3 0.20
SiO2 2.29
Fe2O3 0.05



#27 bciskepottery

bciskepottery

    Advanced Member

  • Members
  • PipPipPip
  • 1,408 posts
  • LocationNorthern Virginia

Posted 04 March 2014 - 11:10 AM

http://www.frogpondp...reek-shino.html

From John Hesselberth's Frog Pond Pottery site (Ron's partner in Glazes).

#28 JBaymore

JBaymore

    Moderator

  • Moderators
  • 2,886 posts
  • LocationWilton, NH USA

Posted 04 March 2014 - 11:13 AM

Note that that above analysis from John's site is the original with albany slip.

 

One mol of Albany has almost one more mol of silica compared to Alberta.  It is also well higher in alumina and iron.

 

With Albany instead of Alberta... it is a very different glass...... with alumina just over top limit, silica in the mid range of limit.  Those two changes alone affect the stability greatly in a positive direction.  (There is still that ioversupply of lithium and the solubility issue.)

 

The changing of the original Falls Creek recipe using Albany Slip to one using Alberta Slip seems to have been done by someone with what is known as a "materials based" approach to glazes........ which ignores molecular realities a lot.  Alberta Slip is a slip clay sort of like Albany... so just sub them.  It does not exactly work that way.

 

And also note that Ron is the more serious "tech weenie" of the duo. ;)

 

best,

 

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


John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#29 bciskepottery

bciskepottery

    Advanced Member

  • Members
  • PipPipPip
  • 1,408 posts
  • LocationNorthern Virginia

Posted 04 March 2014 - 11:44 AM

John,

The reformulation version uses Alberta Clay or Albany Slip substitute. Would using one of the substitutes (e.g., Hendley or Krakowski) be preferable to Alberta Clay?

http://www.potters.o...ubject00435.htm

Bruce

#30 Roberta12

Roberta12

    Advanced Member

  • Members
  • PipPipPip
  • 128 posts
  • LocationColorado

Posted 04 March 2014 - 12:39 PM

I went back and reread a thread about lithium carb.   It was from Nov 2012.   I had asked about that bowl that the cranberries attacked.   The same info from John came up then as now.   I called the author of the article after that happened and she assured me it was something she had never seen.  She urged me to try the glaze again and to run the cranberry test.  Since that keeps coming up negative, I went my merry way and have been using that recipe since then.  I will say that I mostly use it on the outside of things.   But....after reading all of this, I will just use it on non functional pieces and find a new favorite glaze.  Thanks so much to everyone on this forum for keeping me on the straight and narrow. 

 

Big Lou! Disregard what I said about FCS!!!  

 

Moral of the story....really dig into the chemistry of a glaze....even if it is published in a respected magazine!!  :)



#31 bciskepottery

bciskepottery

    Advanced Member

  • Members
  • PipPipPip
  • 1,408 posts
  • LocationNorthern Virginia

Posted 04 March 2014 - 03:00 PM

Attached File  Albany.png   43.13KB   1 downloads

Here's a comparison of Albany Slip, Alberta Slip and two Albany Slip substitutes.

#32 Min

Min

    Advanced Member

  • Members
  • PipPipPip
  • 429 posts
  • LocationCanada

Posted 04 March 2014 - 04:00 PM

attachicon.gifAlbany.png

Here's a comparison of Albany Slip, Alberta Slip and two Albany Slip substitutes.

 

You know if you keep posting interesting things like this I'm never going to get any work done! 

This is what I came up with to more closely match the original albany slip recipe. (I still wouldn't use it though because of the lithium levels)

 

falls creek shino with red art etc

Gerstley Borate 18.00
Lithium Carbonate 6.50
Minspar 200 10.80
Silica 8.50
Redart 45.70
EP Kaolin 2.30
Talc 2.30
Calcium Carbonate 5.80
99.90

CaO 0.39*
Li2O 0.28*
MgO 0.16*
K2O 0.08*
Na2O 0.08*
P2O5 0.00*
TiO2 0.02
Al2O3 0.31
B2O3 0.22
SiO2 2.65
Fe2O3 0.07



#33 Babs

Babs

    Advanced Member

  • Members
  • PipPipPip
  • 890 posts

Posted 04 March 2014 - 05:04 PM

 

attachicon.gifAlbany.png

Here's a comparison of Albany Slip, Alberta Slip and two Albany Slip substitutes.

 

You know if you keep posting interesting things like this I'm never going to get any work done! 

 

Yes, I will acknowledge here that this site is addictive. I thought it was only me as I have been potting in the wilderness for decades!

I now say, only 1 session and two articles, not strong enough!

EDIT

What, if any, are acceptable levels of Lithium for foodsafety, given all the variancies of firing et al



#34 Biglou13

Biglou13

    Advanced beginner pottery, Advanced in other art

  • Members
  • PipPipPip
  • 933 posts
  • LocationNorth Florida

Posted 04 March 2014 - 08:55 PM

Can you just up the silica, rio, alumina... To bring the chemistry closer, and more stable (ish)
If so how much?
I'm sure I'm over simplifying.....
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

#35 Min

Min

    Advanced Member

  • Members
  • PipPipPip
  • 429 posts
  • LocationCanada

Posted 04 March 2014 - 09:14 PM

Can you just up the silica, rio, alumina... To bring the chemistry closer, and more stable (ish)
If so how much?
I'm sure I'm over simplifying.....

That is easy enough to do but that's not the main issue with this glaze. The lithium is way to high and can cause both crazing and shivering on the same piece. Slivers of glaze can pop off the pot. Bowl of salad with glass on the side type scenario. Crystals growing in raw lithium glaze slurry can be a problem too.



#36 Roberta12

Roberta12

    Advanced Member

  • Members
  • PipPipPip
  • 128 posts
  • LocationColorado

Posted 05 March 2014 - 12:05 AM

I haven't had one instance of shivering or crazing.  Not one.   I am not sure why, but I haven't.  I have used these glazes a lot on knitting bowls.  But, I have had the crystals growing in the glaze buckets.....I sieve them out.   Should I not be doing this??  



#37 JBaymore

JBaymore

    Moderator

  • Moderators
  • 2,886 posts
  • LocationWilton, NH USA

Posted 05 March 2014 - 09:18 AM

By seiving the crystals out you are removing some of the soluble materials from the glaze... and alterring its chemistry in the fired form.  THAT may be why you are not having issues ;) .... the main solubles in that glaze are lithium and sodium compounds.

 

So the calc that shows is not the stuff on the pots.  Which in this case may be better if the look is still good.

 

You can do tests steadily dropping the lithium carb and see what the glaze looks like as that is disappearing.  MAYBE it will be ok without it.  (Haven;t calculated the glaze without the Li2O.)

 

best,

 

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


John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com

#38 timbo_heff

timbo_heff

    Advanced Member

  • Members
  • PipPipPip
  • 169 posts
  • LocationMA / NY

Posted 05 March 2014 - 01:10 PM

Sheffield Albany slip sub is really really close to the original.  It is sourced just 50 miles from the orig and with a couple additions it is darn close visually and chemically:

http://www.sheffield...-p/rmalbsub.htm



#39 Biglou13

Biglou13

    Advanced beginner pottery, Advanced in other art

  • Members
  • PipPipPip
  • 933 posts
  • LocationNorth Florida

Posted 05 March 2014 - 04:36 PM

can some give me their opinion and or facts on  glazes with lithium.

 

if the chemicals are "glassed"  and aren't leaching  then shouldn't this be safe?


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

#40 Min

Min

    Advanced Member

  • Members
  • PipPipPip
  • 429 posts
  • LocationCanada

Posted 05 March 2014 - 10:52 PM

can some give me their opinion and or facts on  glazes with lithium.

 

if the chemicals are "glassed"  and aren't leaching  then shouldn't this be safe?

 

Good article on lithia here:http://digitalfire.c.../oxide/li2o.htm






0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users