stephani stephenson on tue 1 may 07
ron, ivor
this is anecdotal only , but i have seen tin
opacified glazes blush quite ruddy pink when there
was no chrome in the glaze or on the piece, but when
there were other pieces in the kiln with glazes
containing chrome.
fuming , volatilaztion of some sort would seem to be
the logical explanation at least as far as i could
figure.
Stephani Stephenson
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Ron Roy on tue 1 may 07
Hi Stephani,
I can get even more complicated - when the fuming happens it coats the
inside of a kiln and furniture as well - in the end all you need is a tin
glaze to get pink because every time the kiln is fired the fumes are
produced again.
RR
>ron, ivor
>this is anecdotal only , but i have seen tin
>opacified glazes blush quite ruddy pink when there
>was no chrome in the glaze or on the piece, but when
>there were other pieces in the kiln with glazes
>containing chrome.
>fuming , volatilaztion of some sort would seem to be
>the logical explanation at least as far as i could
>figure.
>Stephani Stephenson
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Ivor and Olive Lewis on wed 2 may 07
Dear Stephani Stephenson, =20
Thanks for joining in on this one.
I thing it is agreed that something is happening and I suppose the best =
way to describe it is as "Volatilisation"
But the melting temperature of Chromium Sesquioxide, the green stuff =
that some of us use melts way above the pottery firing range, 2330 deg C =
and it boils, which is also called volatilisation, at 3000 deg C. So, if =
it is a case of atoms and molecules escaping then a lot of the other =
compounds we use which have lower melting and boiling points should be =
doing the same thing.
So, if it is Chromium that is escaping to give that red blush we have to =
ask, "What is the Chemistry" which is the logical thing to do.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Kathi LeSueur on wed 2 may 07
stephani stephenson wrote:
>ron, ivor
>this is anecdotal only , but i have seen tin
>opacified glazes blush quite ruddy pink when there
>was no chrome in the glaze or on the piece, but when
>there were other pieces in the kiln with glazes
>containing chrome.
>fuming , volatilaztion of some sort would seem to be
>the logical explanation at least as far as i could
>figure.
>Stephani Stephenson
>
>
>
>
I also get this effect with whites opacified with titanium.
Kathi
stephani stephenson on thu 3 may 07
thanks for the tips Ron and Tim
and Kathi, interesting what you say about titanium
i was working with one glaze in particular a few years
back that i could not for the life of me , get a green
using any stain with chrome in it, and the copper
greens were not great.
it made great browns, but every single chrome stain
(including mason stains, would blush maroon brown,
some firings more than others...there was no tin in
the glaze and i removed the traces of zinc
(at first i used some frit 3269 which has a bit of
zinc)
but still got the same effect. coincidentally i did
try shifting that glaze over , lessening the calcium
, increasing magnesium, just to see what
it did to color and surface qualities.
still i was puzzled at what kept influencing the
original glaze so strongly, no tin no zinc, yet
periodically a whole kiln blushing root beer
maroon... it had titanium as well as a lot of calcium,
thanks for the tips !
Stephani
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stephani stephenson on thu 3 may 07
P>S the other factor i noticed with this glaze , when
i did a currie grid with chrome as a colorant was
that the alumina silica ratio definitely affected the
color response.... it has been a few years since i did
these tests.
Stephani
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