bill edwards on sun 31 jul 05
Steve's chemistry information was interesting,
helpful. I think I may be saying something similar
here, not sure? But since rutile is primarily composed
of TiO2 and Fe203 with some traces of other materials,
wouldn't the iron allow for the tinge of yellow within
the complexity of the crystals under light where it
reflects? (Slow cooling should help these grow and
become even more glorious)additions of any iron
content should enhance the depth to a point where it
goes brown or tan.
Excessive amounts should opacify in particular where
long firing and cooling cycles are used. Used alone
and at or about 8% I seem to get a nice peach color in
some glaze bases I have. In others and using smaller
increment I get a yellow hue. This suggests to me that
the clarity of the base and the flux oxides play an
obvious role in achieving the desired end based on
some of my calculations/experiences of the past. I
have tightened up the action by introducing more Al203
or sometimes Silica and see a change. (Common reason
for exploring base glaze potentials with varying
colorant oxides)Ron and John have added a great deal
to this chemistry through heat work processes coupled
with good glaze understanding. (I give many thanks to
all Clayarters who have donated any time to our craft
here). I used them as a reference point since (besides
myself) seem to use heat work and chemistry as a main
stay for their research in the latest of ^6 ox.
experiments.
Stabilizers and various flux oxides play in on all
this as they should when maximizing the efforts to
obtain crystal growth and bright shimmering yellows
where iron is present. Anyone here tried using yellow
iron oxide or ocher with rutile and perhaps have
pictures of this somewhere? There would be traces of
MgO, MnO with a lower iron content and some Al203 and
SiO2 than that of red iron perhaps broadening the
scope of yellows available under oxidation atmospheres
when using ochre with rutile. LOI on ochre seems to be
just over 10% if you take that into accounting. Most
re-printed analysis leave all these minor things out.
I don't! Does it make a difference in the fired
outcome? I am sure there could be more long on-going
discussions on this.
Heres additional information on XRD and volumetric
analysis. PDF. Page 3 and 4 are most interesting. This
will detail how irons of any kind are not as similar
as we potters would like and therefore the results
vary often.
(done on baroque paintings)
www.iic.cas.cz/~grygar/ABC-earths.pdf
I would probably have to try this with a blend of GB
instead of frit to begin but much testing would need
to be done and also the GB I have on hand would last a
lifetime for me so the results would remain consistent
only from this side of the paper unless you are lucky
enough to have obtained the exact same batch materials
that I have. Your consistency might start with 3134 or
3195 which contains less Sodium and calcium but more
AL203 if your not using GB or not wishing to go back
there for any reason. Frits are a more uniform source
as would be synthetic irons!
Bill Edwards
Edmar Studio and Gallery
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Steve Slatin on sun 31 jul 05
Bill --
I suspect the largest difference between what we said
it that it was easier to understand the way you said
it. And certainly the small differences in chemical
composition will make other differences in a glaze
outcome. Since Ti and Fe are the primary components
of rutile, and since they both can show yellow
(though, in the case of Fe, more often brown) in
oxidation, it seems likely one or the other is key.
I'll do my test in my next glaze load, and get a
little information about what works, which may help me
to speculate about why. I'm not going to change my
firing ramp, though, as I now have a half-dozen glazes
that are good and reliable in appearance with the ramp
I'm using. I'm just too invested to experiment much
there.
Best wishes -- Steve Slatin
--- bill edwards wrote:
> Steve's chemistry information was interesting,
> helpful. I think I may be saying something similar
> here, not sure? But since rutile is primarily
> composed
> of TiO2 and Fe203 with some traces of other
> materials,
> wouldn't the iron allow for the tinge of yellow
> within
> the complexity of the crystals under light where it
> reflects? (Slow cooling should help these grow and
> become even more glorious)additions of any iron
> content should enhance the depth to a point where it
> goes brown or tan.
>
Steve Slatin --
Frail my heart apart and play me little Shady Grove
Ring the bells of Rhymney till they ring inside my head forever
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