Barry Hall on tue 2 jan 07
When I pull bisque ware from my electric kiln it is pure white. After
I rinse and let it dry it develops a yellow cast. Could this be due
to my water? I have city tap water and it is reportedly pretty
clean. Is this common?
Marek & Pauline Drzazga-Donaldson on tue 2 jan 07
Dear Barry,
when just out of the kiln it is totally dry and so seemingly white, when =
water is taken in it shows its true colour. When bisque sits around it =
absorbs the ambient moisture and will become a darker hue from kiln =
fresh ware, so unless your water is saturated with iron oxide etc it =
should not "colour" the ware.
Happy potting Marek
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Marcia Selsor on tue 2 jan 07
On Jan 2, 2007, at 5:06 AM, Barry Hall wrote:
> When I pull bisque ware from my electric kiln it is pure white. After
> I rinse and let it dry it develops a yellow cast. Could this be due
> to my water? I have city tap water and it is reportedly pretty
> clean. Is this common?
It is sulphur or salts coming from the clay either from local water
or leaching from
the body because it wasn't bisque high enough or soaked long enough
to burned them out. I saw that oftern in Billings, MT and I thought
our water was pretty clean.
Marcia Selsor
http://marciaselsor.com
lela martens on tue 2 jan 07
Hi,
The same thing happens to my Laguna B mix bisque ware.
I have never worried about it, doesn`t seem to do any harm.
Lela
I have city tap water and it is reportedly pretty
>clean. Is this common?
>
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Graeme Anderson on tue 2 jan 07
Are you using a commercial clay, or preparing your own?
Could the yellow be caused by a soluble vanadium salt stain? This
happened on some of the white clays I dig locally. Never noticed it on
any buff or dark clays.
The yellow disappeared in the glaze firings.
Cheers. Graeme.
Bonnie Staffel on wed 3 jan 07
Barry, when I was doing pit firing at a friend's studio, I noticed that his
water had a sulfur odor to it. My washed pots turned yellow to which I
attributed it to the sulfur. You might test your water for this chemical.
However, I believe that the yellow color evaporated over time as I have
nothing that shows the yellow any more. As sulfur is a gas, that may be
what is happening.
Bonnie Staffel
http://webpages.charter.net/bstaffel/
http://vasefinder.com/bstaffelgallery1.html
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Ann Testa on wed 3 jan 07
I asked this question awhile back & never got any answers.
Why do horsehair raku pots get yellow spots? Is it the same
cause as for yellow bisque or is it related to the terra sig or
the propane gas? I just pulled out a pot that had been stored
& it has lots of yellow spots on it. It did not look like that when
I stored it. Does anyone have an answer for me?
Ann Testa
_www.clayartgallery.com_ (http://www.clayartgallery.com)
Randall Moody on thu 4 jan 07
My first guess is that it is the same reason bisque does it. It probably has
to do with raku not being vitrified and the salts leaching out of the ware.
On 1/3/07, Ann Testa wrote:
>
> I asked this question awhile back & never got any answers.
> Why do horsehair raku pots get yellow spots? Is it the same
> cause as for yellow bisque or is it related to the terra sig or
> the propane gas? I just pulled out a pot that had been stored
> & it has lots of yellow spots on it. It did not look like that when
> I stored it. Does anyone have an answer for me?
>
> Ann Testa
> _www.clayartgallery.com_ (http://www.clayartgallery.com)
>
>
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Marcia Selsor on thu 4 jan 07
On Jan 3, 2007, at 7:48 PM, Ann Testa wrote:
> I asked this question awhile back & never got any answers.
> Why do horsehair raku pots get yellow spots? Is it the same
> cause as for yellow bisque or is it related to the terra sig or
> the propane gas? I just pulled out a pot that had been stored
> & it has lots of yellow spots on it. It did not look like that when
> I stored it. Does anyone have an answer for me?
>
> Ann Testa
> _www.clayartgallery.com_ (http://www.clayartgallery.com)
>
I haven't had that experience with my horse hair pots , but again it
could be sulphur migrating to the surface from either water or your
clay or the terra sig. If you are bisque firing to a low temp to
preserve the terra sig's sheen, maybe try firing slower and holding
at the peak temperature of ^012-09.
That may or may not help. I never considered it coming from the propane.
Does anyone else know if it could come from the propane?
Marcia Selsor
http://marciaselsor.com
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