Erin Hayes on thu 28 aug 97
Hi all!
While I was working on my class guide for fall term, I came across the
section on scumming and remembered a question I wanted to put to
everyone (the answer to which my students invariably want and I can't
provide them for certain) -
Have you ever seen a yellowish stain develop on a freshly glazed piece
as it dries?
We sometimes see a light yellow cast come up on frshly glazed work in
the studio. Usually it is when the A/C is on, sometimes it is shaped
like handprints and sometimes not. Sometimes it will persist after the
Cone 10 firing if it has appeared on a white or clear glaze, so it must
be inorganic.
I keep thinking this must be a different sort of scumming than I've seen
in clay bodies, but I wanted to know what all-uh-y'all think.
Erin. (Waiting gratefully to be dazzled by an explanation from someone
who knows more about it...)
Sarah Barnes on fri 29 aug 97
HI
Don't know if this is correct, but I always thought the yellow scum was
the salts from the glaze coming to the surface. This seems to happen most
with shino glazes. Curious to know what other think.
Sarah
M Richens on mon 1 sep 97
In article <3404C7BA.6881@ctc.edu>, Erin Hayes
writes
>----------------------------Original message----------------------------
>
>Have you ever seen a yellowish stain develop on a freshly glazed piece
>as it dries?
>
>We sometimes see a light yellow cast come up on frshly glazed work in
>the studio. Usually it is when the A/C is on, sometimes it is shaped
>like handprints and sometimes not. Sometimes it will persist after the
Hi Erin,
Occasionally you can get some surface effects like this from flotation
due to having the slip underset. too much free water and can be cured by
small additions of an electrolyte _solution_ of such as Mag Sulphate
(epsom salts) or Calcium chloride.
HTH
Max
--
Max Richens max@richens.demon.co.uk +44 (0) 1925756241
Enamel Consultant - Ceramist - Analyst programmer
Software for Batch Formulation and Millroom control.
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