Paula Sibrack on sun 15 nov 98
Two of my high school ceramic students glazed the insides of large coil pots
with a commerical blue x06 glaze (Ammaco Dark Blue). The next day there was a
yellow tint on the outside of one pot, which was not yet glazed, and a yellow
tint on the newspaper wrapped around the outside of the second pot (outside
also unglazed) . The kids were curious and I don't have the answer as to why.
My guess is that some salts have precipatated to the surface. Do any of you
glaze mavens know the right answer? TIA, Paula Sibrack Marian, in the woods of
Sherman, CT, looking down on Candlewood Lake.
Bob and Hulda on tue 17 nov 98
>Two of my high school ceramic students glazed the insides of large coil
pots
>with a commerical blue x06 glaze (Ammaco Dark Blue). The next day there was
a
>yellow tint on the outside of one pot, which was not yet glazed, and a
yellow
>tint on the newspaper wrapped around the outside of the second pot (outside
>also unglazed) . The kids were curious and I don't have the answer as to
why.
>My guess is that some salts have precipatated to the surface. Do any of you
>glaze mavens know the right answer? TIA, Paula Sibrack Marian, in the woods
of
>Sherman, CT, looking down on Candlewood Lake.
>Dear Paula,
This happens when clays have been in a container which
was used for holding casting slip and in contact with sodium silicate.
Do not worry about this if you are bisque firing as it will then have no
effect on glaze firing,but I have had the experience of raw glazing pots
with this yellowing and every pot the glaze crawled badly and a lot of it
[the glaze] ran off onto my shelves.
Regards Bob
Hollis
Leona Stonebridge Arthen on sat 21 nov 98
I have noticed that effect, too. Both on pots glazed on the inside and on
pots which have been rinsed in tap water in the town I used to work in, the
unfired pots would leach out a yellow salt line as they dried. I assumed
it was something in the water. It goes away completely when the pot is
fired. Now my glazes are made and pots are rinsed in well water and I
don't get that happening. It comfirms my suspicions about the water.
Leona
---
Leona Stonebridge Arthen
leona@javanet.com
Worthington, Massachusetts/USA
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