Lili Krakowski on sun 22 apr 07
It has been my long time impression that Fe2O3 at c. 6 is neither a flux,
nor refractory in electric firing, and a flux in reduction. Someone
mentioned the flux part--but I think that is ONLY in reduction. Right?
Wrong?
Lili Krakowski
Be of good courage
Vince Pitelka on mon 23 apr 07
> It has been my long time impression that Fe2O3 at c. 6 is neither a flux,
> nor refractory in electric firing, and a flux in reduction. Someone
> mentioned the flux part--but I think that is ONLY in reduction. Right?
> Wrong?
Lili -
I thought that Ron or John would respond to this, and perhaps they still
will. Red iron oxide is a refractory, but becomes a flux when it turns into
black iron oxide, which happens in a reduction atmosphere, or in an
oxidation atmosphere when it reaches a certain temperature. I seem to
rememember that the change takes place before midrange temperatures.
Perhaps someone has more precise information on the specific temperature at
which red iron turns to black iron. If it were not for this change, it
would not be possible to get black temmokus in an electric kiln.
- Vince
Vince Pitelka
Appalachian Center for Craft, Tennessee Technological University
Smithville TN 37166, 615/597-6801 x111
vpitelka@dtccom.net, wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Ron Roy on wed 25 apr 07
Hi Lili,
I'm not sure but I think a bit of a flux at the high temperatures - and if
a lot more of a flux but I have not done any experiments.
Certainly more of a flux in reduction - Hamer says a strong flux because it
melts quite low (800C) when reduced so that makes it comparable to the
alkaline fluxes. Actually I don't think as strong as that.
It would be an interesting experiment - to find out just how much influence
it does have at different temperatures and amounts and atmosphers.
RR
>It has been my long time impression that Fe2O3 at c. 6 is neither a flux,
>nor refractory in electric firing, and a flux in reduction. Someone
>mentioned the flux part--but I think that is ONLY in reduction. Right?
>Wrong?
>
>Lili Krakowski
>Be of good courage
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Charles Moore on wed 25 apr 07
Ron,
About two years ago, you got me to test a "marble" of Red Art clay fired to
^6 in oxidation and ^6 in reduction, each in a pinch pot. The red art
marble adhered (stuck) to the pinch pot in reduction, but not in oxidation.
That certainly supports your position below.
Charles Moore
Sacramento, CA
----- Original Message -----
From: "Ron Roy"
To:
Sent: Wednesday, April 25, 2007 11:25 AM
Subject: Re: Red Iron Oxide as flux
> Hi Lili,
>
> I'm not sure but I think a bit of a flux at the high temperatures - and if
> a lot more of a flux but I have not done any experiments.
>
> Certainly more of a flux in reduction - Hamer says a strong flux because
> it
> melts quite low (800C) when reduced so that makes it comparable to the
> alkaline fluxes. Actually I don't think as strong as that.
>
> It would be an interesting experiment - to find out just how much
> influence
> it does have at different temperatures and amounts and atmosphers.
>
> RR
Ivor and Olive Lewis on fri 27 apr 07
Dear Ron Roy ,
I had a look at what Frank Hamer has to say about Iron Oxide in his =
entry "Iron Oxide". Yes, he does tell us that Black Iron Oxide becomes a =
glaze flux at temperatures over 900 deg C. But is that a melting event ?
Kay and Laby give the following values which are confirmed by Hamer' in =
his "Table of mineral constants". Black Iron Oxide (Magnetite) Fe3O4 has =
a decomposition temperature of 1538 deg C and Black Iron oxide Fe0.95O =
(Hamer FeO) has a melting point of 1420 deg C.
So, what happens in a glaze recipe at 900 deg C ?
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Ivor and Olive Lewis on fri 27 apr 07
Dear Charles Moore,=20
You say <clay fired to
^6 in oxidation and ^6 in reduction, each in a pinch pot. The red art =
marble adhered (stuck) to the pinch pot in reduction, but not in =
oxidation.>>
An interesting observation. I might explain this by suggesting that the =
Tamman Point, the temperature above which Sintering will commence is =
higher for red iron oxide than for black iron oxide, by virtue its =
higher melting point. FeO would be expected to commence sintering around =
710 deg C, Fe2O3 around 840 deg C.
That these temperatures are so much lower than Cone 6 may suggest a =
reason other than the fluxing nature of Iron oxides for your =
observation.
Do you think there could be other influences ?
Best regards,
Ivor Lewis.
Redhill,
South Australia.
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