Karin Givon on mon 30 jun 08
Doesn't flux mean melt? And doesn't stuff melt whether it's oxidized
or reduced?
That is to say, iron melts at whatever temperature it melts at, which
I'm not gonna look up right now, but...... and so do ze other oxides,
( at their respective temperatures) and they all affect each other-
both in color and 'flow' (melt). and texture and depth and everything
else you could think of to say about glazes.
And yes! YOU too could spend your life figuring all this out, just
like many of us are! Gives us something to do. Something to think
about.
What a great adventure we're on.
Henrietta
On Jun 30, 2008, at 7:43 PM, Jim Brooks wrote:
It is my impression that iron is a strong flux.. but only in
reduction !! No
fluxing action in oxidation. .. Im sure John or someone can
correct me if
this is wrong. BUT, the iron does react and affect other oxides used
to color
our glazes and clays.. So, yes, you will get a different glaze
color /affect
on the different clay bodies...
Jim in Denton
**************
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Wyndham Dennison on mon 30 jun 08
> Hi Glazemakers,
>
> I have been testing a glaze on red and white clays, and have noticed a
> difference in the results in the surface texture between red and white
> clays even with the same batches of glaze, dipped at the same time.
> I'm wondering if the iron in the red glaze would make the glaze
> glossier on the red clay. The glazes come out much more matte on the
> white clay.
Iron is a fluxing agent and the 2 different clays most likely mature at different temps even though they may both say cone 6. Likely the red clay matures at a slightly lower temp and even from batch to batch clays will differ in the maturing temp. Remember also that some of the clay is melted into a glaze. Since "Clay" is made of several different components that are blended to mature at a certain temp range, the glazes need to be adjusted to achieve the proper functional bond of clay and glaze. If you were to reduce the refractory(clay) ingredient by a small amt and or increase the fluxing ingredient by a small amt, in a line blend, this may help achieve the look and function of the glaze.
Hope this helps Wyndham
Jim Brooks on mon 30 jun 08
It is my impression that iron is a strong flux.. but only in reduction !! No
fluxing action in oxidation. .. Im sure John or someone can correct me if
this is wrong. BUT, the iron does react and affect other oxides used to color
our glazes and clays.. So, yes, you will get a different glaze color /affect
on the different clay bodies...
Jim in Denton
**************
Gas
prices getting you down? Search AOL Autos for fuel-efficient used cars.
(http://autos.aol.com/used?ncid=aolaut00050000000007)
Hank Murrow on tue 1 jul 08
On Jun 30, 2008, at 7:43 PM, Jim Brooks wrote:
> It is my impression that iron is a strong flux.. but only in
> reduction !! No
> fluxing action in oxidation. .. Im sure John or someone can
> correct me if
> this is wrong. BUT, the iron does react and affect other oxides
> used to color
> our glazes and clays.. So, yes, you will get a different glaze
> color /affect
> on the different clay bodies...
Jim;
Iron will reduce spontaneously around cone 8_9 even though the kiln
is in oxidation. John Britt has developed beautiful iron spot glazes
which only work in an oxidation firing due to this property of iron.
Cheers, Hank
Joseph Herbert on tue 1 jul 08
This example doesn't mean too much, except to point out how complex this
topic is:
The Melting point of aluminum is 1220.58 °F.
The melting point of alumina is 3729 °F.
The one that is totally reduced melts at a temperature 2500 degrees lower
than the totally oxidized material. Clearly, the reduced state here is
easier to melt.
Of course, the processes that occur during glaze melting are significantly
more complex that this simple example. Much of the action takes place in a
viscous, highly cross-linked liquid composed of metallic and semi-metallic
oxides. The effects of reduction on this goo are controlled by the ability
of the kiln atmosphere carbon monoxide to penetrate the mass, travel to an
oxygen, and grab it.
Anyway, in the world of oxide chemistry and alloys both, combinations of
materials melt at different temperatures depending on the combinations. As
a well known example, 60/40 solder melts at a lower temperature than either
lead or tin. Things only just melt when they are alone.
Joe
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG]On Behalf Of Karin Givon
Sent: Monday, June 30, 2008 11:01 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: red and white clay glazes
Doesn't flux mean melt? And doesn't stuff melt whether it's oxidized
or reduced?
That is to say, iron melts at whatever temperature it melts at, which
I'm not gonna look up right now, but...... and so do ze other oxides,
( at their respective temperatures) and they all affect each other-
both in color and 'flow' (melt). and texture and depth and everything
else you could think of to say about glazes.
And yes! YOU too could spend your life figuring all this out, just
like many of us are! Gives us something to do. Something to think
about.
What a great adventure we're on.
Henrietta
On Jun 30, 2008, at 7:43 PM, Jim Brooks wrote:
It is my impression that iron is a strong flux.. but only in
reduction !! No
fluxing action in oxidation. .. Im sure John or someone can
correct me if
this is wrong. BUT, the iron does react and affect other oxides used
to color
our glazes and clays.. So, yes, you will get a different glaze
color /affect
on the different clay bodies...
Jim in Denton
**************
Gas
prices getting you down? Search AOL Autos for fuel-efficient used cars.
(http://autos.aol.com/used?ncid=aolaut00050000000007)
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Ivor and Olive Lewis on wed 2 jul 08
Dear Henrietta,
The Karin Givon confused me.
You ask "Doesn't flux mean melt? And doesn't stuff melt whether it's
oxidized
or reduced?"
Well yes, it does, and yes, they do.
But "Flux" has several meanings. So misunderstands arise when first
melting is attributed to materials that are highly refractory, for
example Magnesium Oxide, Calcium Oxide and other group 2 oxides or
Transitional Metal Oxides like Red Iron Oxide. Then a second meaning
has to be considered. I like to thing in terms of "Making something
flow or move with greater ease", and in that context, those refractory
oxides, when dissolved in a silicate solution, change the viscosity of
the melt so that the glaze flows faster and farther.
Although this information is in the text books it is not always
explained clearly.
And I agree with you, glazing is a series of adventures along a life
long pathway.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Karin Givon on thu 3 jul 08
Thank you Ivor! Those flow-ey ones are the ones I'm interested in for
oxy glazing--we need some movement to make it look less like latex
paint! And the depth, of course, is always desireable. Changing from
many many years of reduction to oxidation is such a challenge, only
lately fun.
And I use Henrietta Peeorplethorpe when I feel funny, or dumb. A
pseudonym for "huh?"
Karin/henrietta
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