Jeff Tsai on sun 23 feb 03
I'd like to throw out a rumour and see what people with greater technical
experience can tell me.
I've heard tell that Shinos can change over long periods of time dur to
something having to do with the high amount of soda ash added to some shino
glazes. I don't know what happens, but have heard this said about shino
glazes that sit around for more than a couple months.
Is there any hint of truth or possibility to such a claim?
-jeff tsai
Paul Herman on sun 23 feb 03
Jeff,
The shinos in my shop seem to store just fine. They are used twice a
year, and show no sign of changing. One contains 19% soda ash, and the
buckets tend to get crusty around the top, if the glaze contains soluble
materials. Scraping the sides down and screening before use is advised.
Good glazing,
Paul Herman
Great Basin Pottery
423-725 Scott Road
Doyle, California 96109 US
potter@psln.com
----------
>From: Jeff Tsai
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Re: Shino Glaze changing over time
>Date: Sun, Feb 23, 2003, 1:28 AM
>
> I'd like to throw out a rumour and see what people with greater technical
> experience can tell me.
>
> I've heard tell that Shinos can change over long periods of time dur to
> something having to do with the high amount of soda ash added to some shino
> glazes. I don't know what happens, but have heard this said about shino
> glazes that sit around for more than a couple months.
>
> Is there any hint of truth or possibility to such a claim?
>
> -jeff tsai
Hank Murrow on sun 23 feb 03
On Sunday, February 23, 2003, at 01:28 AM, Jeff Tsai wrote:
> I've heard tell that Shinos can change over long periods of time dur to
> something having to do with the high amount of soda ash added to some
> shino
> glazes. I don't know what happens, but have heard this said about shino
> glazes that sit around for more than a couple months.
>
> Is there any hint of truth or possibility to such a claim?
>
Dear Jeff;
There IS some truth to this claim. The truth resides in the fact that
soda ash (and any other soluble) is carried into the bisque with the
water, unlike the other materials which are left on the surface. Thus,
pots absorb more of the soda ash each time you glaze, and the 'recipe'
therefore changes with each glazing session. That is one of the reasons
industry relies so much on frits. They find these or any changes
anathema. Any glaze that contains solubles will exhibit this behavior,
and in proportion to the amounts and solubility of the material.
It is not the amount of time that passes, but rather the amount of
bisque that has been dipped in the bucket.
Cheers, Hank in Eugene (but soon in LA & San Diego)
Ron Roy on mon 24 feb 03
Hi Jeff,
seems to me that if a glaze has any solubles in it - as you glaze the
solubles being drawn into the clay get "taken" away from the glaze - so
each time you glaze they get less.
Can also be - that some of those solubles crystalize out.
In both cased the glaze will be altered - does somebody know how to measure
solubles so they can be checked?
RR
>I'd like to throw out a rumour and see what people with greater technical
>experience can tell me.
>
>I've heard tell that Shinos can change over long periods of time dur to
>something having to do with the high amount of soda ash added to some shino
>glazes. I don't know what happens, but have heard this said about shino
>glazes that sit around for more than a couple months.
>
>Is there any hint of truth or possibility to such a claim?
>
>-jeff tsai
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
RJones7582@AOL.COM on wed 26 feb 03
Another consideration with the shinos is if the soda ash is in solution at
the time it is applied to the pot makes a difference in the final appearance
of the glaze. Since it is usually in solution in and when the pot dries the
pot acquires a white surface of soda ash crystals which promotes carbon
trapping and some of the spontaneous marking and patterning of the colors.
If the glaze is warm and therefore the soda ash is in solution rather than
suspended at the time of the application there will be a difference in the
final outcome of the glaze appearance. I think this accounts for some of the
problems with Shinos. Since I spray most of my glazes I stir up my shino
glaze thoroughly then zap it briefly in a microwave before I spray so that I
am sure the soda ash is in solution. Einstein said that mystery is the spice
of life. That is why shino glazes were invented.
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