John Rodgers on thu 17 feb 05
I've run out of Cobalt Oxide. I have plenty of Cobalt Carbonate. I have
NEVER used Cobalt Carb in my Floating Blue and it has performed
extremely well.
But I have a dilema.
I absolutely must make glaze immediately and have no time to wait for a
shipment to get here.
Has anyone had experience in using Cobalt Carb in Floating Blue???
What change in quantity of Cobalt Carbvs Cobalt Oxide to make it work
right??
Did the change look like the other Floating Blue with the Cobalt Oxide??
Any input would be appreciated.
Thanks,
John Rodgers
Chelsea, AL
Sue Cline on fri 18 feb 05
John -- I have always used cobalt carbonate in Floating Blue (because I don't know any better, I guess). The "rule" I learned was to use 2.5 X the amount of cobalt oxide in a glaze recipe to come up with the right amount of cobalt carbonate. ( 1% cobalt oxide = 2.5% cobalt carbonate).
I am not a guru. I am a rookie who has been on this list for a long time. I use floating blue quite a lot (don't have the exact recipe in front of me) and have messed with it enough to know it likes ^5 better than ^6 in my kiln and that it actually looks better (brighter) with a faster cooling cycle than recommended by the masters.
FWIW and YMMV
Sue Cline
Cincinnati, Ohio
Potters' Council Member
-----Original Message-----
From: John Rodgers
Sent: Feb 17, 2005 10:51 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Floating Blue - Cobalt Carb vs Cobalt Oxide
I've run out of Cobalt Oxide. I have plenty of Cobalt Carbonate. I have
NEVER used Cobalt Carb in my Floating Blue and it has performed
extremely well.
But I have a dilema.
I absolutely must make glaze immediately and have no time to wait for a
shipment to get here.
Has anyone had experience in using Cobalt Carb in Floating Blue???
What change in quantity of Cobalt Carbvs Cobalt Oxide to make it work
right??
Did the change look like the other Floating Blue with the Cobalt Oxide??
Any input would be appreciated.
Thanks,
John Rodgers
Chelsea, AL
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Randy McCall on fri 18 feb 05
John=20
I use the same amount of cobalt carbonate and get a nice opaque blue, =
but it is not the dark midnight blue color that is on Chappell's Book =
cover. I was later told to increase the rutile to the iron oxide level =
and change the iron oxide level to the rutile level and leave the cobalt =
carbonate the same. Or you just might want to increase the cobalt =
carbonate to 1.5%.
June Perry on fri 18 feb 05
John,
The carb is weaker than the oxide; but should work fine if you adjust the
formula and add more carbonate.
If you check out the archives, I believe they have an exact mathematical fix
to convert from one to the other.
I usually go on the premise that the oxide is about 35% stronger than the
carb. It probably depends on the make up of the material in question. I think
it can go as high as 50% with a lower quality cobalt carb.
My suggestion would be to go with the lower number if you think you have a
high quality carb and the higher if you think your carb is weaker.
Regards,
June Perry
(anxiously waiting for the either the snows and/or mud to stop at the North
Carolina house so we can grade and get the pad in for the new studio and
kiln!)
_http://www.angelfire.com/art2/shambhalapottery/_
(http://www.angelfire.com/art2/shambhalapottery/)
John Rodgers on sat 19 feb 05
June Perry wrote:
>John,
>
>The carb is weaker than the oxide; but should work fine if you adjust the
>formula and add more carbonate.
>If you check out the archives, I believe they have an exact mathematical fix
>to convert from one to the other.
>I usually go on the premise that the oxide is about 35% stronger than the
>carb. It probably depends on the make up of the material in question. I think
>it can go as high as 50% with a lower quality cobalt carb.
>My suggestion would be to go with the lower number if you think you have a
>high quality carb and the higher if you think your carb is weaker.
>
>Regards,
>June Perry
>(anxiously waiting for the either the snows and/or mud to stop at the North
>Carolina house so we can grade and get the pad in for the new studio and
>kiln!)
>_http://www.angelfire.com/art2/shambhalapottery/_
>(http://www.angelfire.com/art2/shambhalapottery/)
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
>
>
>
>
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