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oops ..not white breaking brown


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#1 jkb

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Posted 24 June 2012 - 11:19 AM

I have been mixing this simple white breaking brown glaze for years. of course, Murphys Law sets in when I mix large batches, anyway i mixed a 5 gal batch this week and the result was not white but a very nutmeg like glaze. I used dark talc, which I don't think I have ever used before. Could that be the culprit???? I of course thought that I had mis measured the Tin Oxide so I added 1/3 more (2%) and retested the glaze and nothing changed. any suggestions how to turn this batch white? I hate throwing away anything especially a glaze with Tin Ox.
I have a great recipe already for nutmeg. Hoping it is a simple solution. suggestions welcome. thanks

White Breaking Brown
Dolomite 13%
Custer Feldspar 31%
frit 3134 18%
China clay 30 %
Talc 8%
Tin Ox 6 %
Black Iron Ox 3%

#2 TJR

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Posted 24 June 2012 - 11:30 AM

Your culprits are the talc and the black iron oxide. Everything else in the glaze is white.
I would make up two tests of 100 grams each.
One with dark talc.
One with regular talc. See if the regular talc remains white.
Unfortunately, you can't make white from brown. You have a nice liner glaze.Sorry about that.
TJR.

#3 jkb

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Posted 24 June 2012 - 01:14 PM

Your culprits are the talc and the black iron oxide. Everything else in the glaze is white.
I would make up two tests of 100 grams each.
One with dark talc.
One with regular talc. See if the regular talc remains white.
Unfortunately, you can't make white from brown. You have a nice liner glaze.Sorry about that.
TJR.



#4 jkb

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Posted 24 June 2012 - 01:14 PM

Your culprits are the talc and the black iron oxide. Everything else in the glaze is white.
I would make up two tests of 100 grams each.
One with dark talc.
One with regular talc. See if the regular talc remains white.
Unfortunately, you can't make white from brown. You have a nice liner glaze.Sorry about that.
TJR.



#5 jkb

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Posted 24 June 2012 - 01:17 PM

THANKS FOR RESPONDING. I HAVE ALWAYS INCLUDED THE BIO IN THE GLAZE. AS FOR THE TALC IT IS USED IN SOME OF MY OTHER GLZES AND HAS NOT HAD ANY EFFECT ON THEM. WILL DO THE TEST WITH LITE TALC.

#6 Mark C.

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Posted 24 June 2012 - 01:53 PM

I have been mixing this simple white breaking brown glaze for years. of course, Murphys Law sets in when I mix large batches, anyway i mixed a 5 gal batch this week and the result was not white but a very nutmeg like glaze. I used dark talc, which I don't think I have ever used before. Could that be the culprit???? I of course thought that I had mis measured the Tin Oxide so I added 1/3 more (2%) and retested the glaze and nothing changed. any suggestions how to turn this batch white? I hate throwing away anything especially a glaze with Tin Ox.
I have a great recipe already for nutmeg. Hoping it is a simple solution. suggestions welcome. thanks

White Breaking Brown
Dolomite 13%
Custer Feldspar 31%
frit 3134 18%
China clay 30 %
Talc 8%
Tin Ox 6 %
Black Iron Ox 3%



If you put black Iron in a white base that will never be all white again-It will break brown as the name implies
This looks like a cone 6 with that frit at 18%??
As far as Talcs
There are some choices and it will effect your glaze-
Out west we have Pioneer talc that Laguna Clay sells-its a grey talc but does go white when fired
also Sierralite which is very white
New York was taken off market due to containing asbestos-it was also white
What I will say is that more than color these talcs melt differently on the finished surface that is say for a satin matt Pioneer flues out and leaves a shiny surface where Sierralite is a bit more matt.
The best talcs where CT-30 and Desert talcs for semi matts which for most are long gone -I still use them as I bought in bulk many years ago
Test a small batch with a few talcs and you will see.
All my experience is high fire cone 10+
Mark


Mark Cortright
www.liscomhillpottery.com

#7 Matt Oz

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Posted 25 June 2012 - 10:12 AM

Could it be possible that your supplier accidentally mixed up Tin ox with Titanium diox.

#8 Venicemud

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Posted 15 October 2012 - 10:20 AM

This may be too little too late but the problem with the glaze recipe is a misplaced decimal point. I tried different talcs and kept getting very nice chocolate colored satin glazes with white speckles and then this weekend I tried 0.3% Black Iron Oxide instead of 3%. The result was a nice smooth very light cream colored satin glaze with brown speckles which is very pleasant to touch. Looks, to me, like an oatmeal glaze with a nice even dispersion of the speckles since it is is the Black Iron Oxide and not something granular that keeps sinking if the glaze isn't stirred constantly. Joan.




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