John Hesselberth on wed 7 jan 04
Hi Tom,
Yes, that is one of the advantages of the cobalt carbonate over the
oxide. Some like those blue specks and use the oxide for that reason.
Others prefer the carbonate which does disperse more easily. Just be
sure to adjust the amount. Is the ratio 1.5 carbonate = 1 oxide? I've
forgotten and don't have my handbook close at hand, but I think that is
close.
Regards,
John
On Wednesday, January 7, 2004, at 08:52 AM, Tom Herndon wrote:
> On occasion some of the glazes I mix that contain cobalt oxide would
> come off the kiln with little blue specks all over. I've since settled
> into the pesky practice of milling the cobalt oxide prior to adding it
> to the glaze as a reliable cure for the blue measles. Could I
> substitute cobalt carb for cobalt ox & achieve a similarly clear
> complexion?
http://www.frogpondpottery.com
http://www.masteringglazes.com
Tom Herndon on wed 7 jan 04
Hello John, all
On occasion some of the glazes I mix that contain cobalt oxide would =
come off the kiln with little blue specks all over. I've since settled =
into the pesky practice of milling the cobalt oxide prior to adding it =
to the glaze as a reliable cure for the blue measles. Could I substitute =
cobalt carb for cobalt ox & achieve a similarly clear complexion?=20
Tom, in Louisville - cold & thankful for clay cups & hot tea
>Date: Mon, 5 Jan 2004 21:59:46 -0500
>From: John Hesselberth
>Subject: Re: Waco Taylor's supply list
>
>On Monday, January 5, 2004, at 08:57 PM, Imbolchottie@AOL.COM wrote:
>
>> WHAT IS THE DIFFERENCE BETWEEN A CARBONATE AND AN OXIDE?
>
>Hi Jonathan,
>
>In some ways, not much. The carbonates become oxides in the kiln by
>giving off carbon dioxide. They do that at various temperatures
>depending on the specific material. But by the time the kiln gets to
>peak temperature the carbonates are all gone. In other ways the
>difference is important. For example red copper oxide is very difficult
>to uniformly disperse in a glaze--you have to use soap or another
>wetting agent to get is dispersed; copper carbonate, on the other hand,
>is easy to disperse. For both cobalt and copper, I personally prefer to
>use the carbonates.
>
>And of course if you have a recipe that says one and you have the other
>you need to appropriately adjust for the molecular weights. But I think
>we better save that for another day.
>
>Regards,
>
>John
>http://www.frogpondpottery.com
>http://www.masteringglazes.com
Ababi on wed 7 jan 04
I believe the reason is not using sieve properly.
By the way- I do it on purpose...
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://ababi.active.co.il
http://www.matrix2000.co.nz/Matrix%20Demo/Ababi.htm
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Tom Herndon
Sent: Wednesday, January 07, 2004 3:53 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: carbonate vs oxide, was Waco Taylor's supply list
Hello John, all
On occasion some of the glazes I mix that contain cobalt oxide would
come off the kiln with little blue specks all over.
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