LINDA BLOSSOM on sun 13 apr 97
I have two glazes that have limited shelf lives. The common ingredient is
lithium carbonate. Is this something that is common knowledge and I am
just figuring it out? What other ingredients contribute to this problem?
Linda Blossom
2366 Slaterville Rd.
Ithaca, NY 14850
607-539-7912
blossom@lightlink.com
http://www.artscape.com
Grimmer on mon 14 apr 97
LINDA BLOSSOM wrote:
>
> ----------------------------Original message----------------------------
> I have two glazes that have limited shelf lives. The common ingredient is
> lithium carbonate. Is this something that is common knowledge and I am
> just figuring it out? What other ingredients contribute to this problem?
>
By limited shelf life, do you mean that the fired result is different for a
fresh batch than it is for a bucket that's been sitting around for a while? If
that's the case, I would suspect the Li is going into solution over time. As
the glaze on the pot dries, the dissolved lithium carb is deposited on the
surface. The older the batch, the more time the Li2CO3 has to dissolve,
and the more that is left on the surface.
Shino-type glazes, where the major soluble material is typically sodium
carbonate, are notorious for 'going bad' (or good, if that's your thing).
Try this test: dip a tile in an old bucket of the glaze in question. As soon
as the sheen disappears, wax over a portion of the glaze and fire with a
regular load of ware. If you can see where the wax was after the firing,
you can bet that solubility is the culprit. This is an effective decoration tool
with shino type glazes!
Some sources of less-soluble Li include petalite, amblygonite, and
spodumene, all lithium feldspathoids. They also contribute other goodies
to the mix, tho.
steve grimmer
carterville illinois
Charles Williams on mon 14 apr 97
Linda,
What do you mean by "limited shelf-life"? Do you mean it cracks, splinters,
etc.? Lithium is usually regarded as a prime component in a glaze to
strengthen the glass and provide enriched colors. Could your problem be that
of a bad fit of the glaze to the clay? You might want to try to find out what
the expansion coefficients are for both the clay and the glazes. Anyone who
has one of the computer glaze calculation programs should be able to help you
with this.
Hope this helps!
Charles
Bill Amsterlaw on mon 14 apr 97
Hi Linda:
You observed that some glazes have a limited shelf life. I have a couple of
ideas:
1.
If a glaze includes partly soluble ingredients, whatever is dissolved in water
travels with the water, not the solids in suspension. If you pour off water
to thicken a glaze, you lose solubles. When you dip, solubles get deposited
in the claybody. Over time, the proportions of materials in the glaze change
as solubles are subtracted.
2.
I think Lithium carbonate may be something like sodium carbonate (soda ash):
They are both defloculants.
About a year ago, Linda Arbuckle wrote the following to Clayart:
>>
Many things can deflocculate a glaze. Some frits, esp. hi alkaline ones like
3110 are somewhat soluble and the soluble salts deflocculate. Softened water
or soft water can deflocculate. Lithium carb deflocculates. We had a cone 10
glaze w/lithium carb that settled badly and applied badly until it was
reformulated to use spodumene as another source of lithium. CMC is a gum, but
Hamer in The Potters Dictionary says its actually sodium carbomethyl... etc.
and deflocculates.
<<
Linda Blossom wrote:
>>
I have two glazes that have limited shelf lives. The common ingredient is
lithium carbonate. Is this something that is common knowledge and I am just
figuring it out?
<<
AKitchens on mon 24 feb 03
I am always seeking new Cone 6 single fire glazes for architectural
sculpture.
Are there certain ingredients I can look for in a glaze formula/recipe
that will help
or hinder the shelf life of the glaze. How long do they keep?
i.e.. lithium according to Linda Blossom in the archives, and wood ash
or highly
fritted glazes according to Capt Mark.
My experience with the only (wood ash) glaze I tried to store produced
muddy dark
chocolate runs after it sat for a while, creamy golden runs when it was
fresh.
(a Val Cushing glaze) The crystals that formed were not re-soluble and were
yellow green glass formers when fired alone.
I single fire at cone 6.
It would be nice not to have to take the time to mix up fresh glazes
every time I glaze.
Though there are brief comments about glaze shelf life in the archives
there
doesn't seem to be a cohesive pattern of thought about the cause.
Doing this alone makes the learning curve so much steeper.
Nan Kitchens
Architectural Clayworks
Tennessee, Key Largo
Bruce Freund on wed 15 oct 03
I had a "famous" potter here the other day and he asked me how long some of
the glazes that I do not use that often had been sitting in those 5 gallon
containers. I responded by saying any where from 6 months to a few years.
His immediate response was that a lot of glazes do not have a very long
shelf life. I really never heard this and wanted to pose the subject to the
list.
thank you
bruce freund
Paul Herman on wed 15 oct 03
Bruce,
You let the famous Potter get away with that, and didn't even try to pin
him down as to WHY he thinks that? He needs to be pressed on that point.
So far as I can tell, none of my glazes have "gone bad". Some have been
sitting in the shop for years. I wonder what he thinks they would
"lose"? Is something escaping from the bucket while I'm asleep? There
are lids on my buckets.
I suspect that fame does not always go hand in hand with rightness.
Best wishes,
Paul Herman
Great Basin Pottery
423-725 Scott Road
Doyle, California 96109 US
potter@psln.com
----------
> I had a "famous" potter here the other day and he asked me how long some of
> the glazes that I do not use that often had been sitting in those 5 gallon
> containers. I responded by saying any where from 6 months to a few years.
> His immediate response was that a lot of glazes do not have a very long
> shelf life. I really never heard this and wanted to pose the subject to the
> list.
>
> thank you
>
> bruce freund
Earl Brunner on wed 15 oct 03
I think you should have pressed your famous person for his rationale for
that. It is true that some ingredients are water soluble to a degree
and the longer they sit; the more might dissolve into the liquid. To
what degree if any that might affect the fired result of the glaze
depends a lot on the glaze, application, and firing of the pieces.
Glazes with little to no water soluble materials in them should last
indefinitely.
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Bruce
Freund
Sent: Wednesday, October 15, 2003 6:49 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Glaze Shelf Life
I had a "famous" potter here the other day and he asked me how long some
of
the glazes that I do not use that often had been sitting in those 5
gallon
containers. I responded by saying any where from 6 months to a few
years.
His immediate response was that a lot of glazes do not have a very long
shelf life. I really never heard this and wanted to pose the subject to
the
list.
thank you
bruce freund
Louis Katz on thu 16 oct 03
Glazes change over time. Especially those with soluble and reactive
ingredients. Gertsley Borate and Lithium Carbonate are good examples of
this. The result over time is a substance, Lithium Borate, that comes
out of solution in large crystals. It takes both boron and lithium with
it and can radically alter a glaze if sieved out.
Shino glazes seem to go through a similar maturing over the course of
a few days. Because solubility is related to temperature, sometimes
glazes look different when applied at different temps. One shino in
school seemed to be wilder in the winter. Most such changes must be
very subtle or non existent as they evade detection.
Louis
Roger Korn on sat 18 oct 03
Hi Louis,
Would this apply to all shinos, or just those using soluble soda ash as a constituent?
Roger
Louis Katz wrote:
...
Shino glazes seem to go through a similar maturing over the course of
a few days. Because solubility is related to temperature, sometimes
glazes look different when applied at different temps. One shino in
school seemed to be wilder in the winter. Most such changes must be
very subtle or non existent as they evade detection.
--
McKay Creek Ceramics
In OR: PO Box 436
North Plains, OR 97133
503-647-5464
In AZ: PO Box 463
Rimrock, AZ 96335
928-567-5699
Louis Katz on sat 18 oct 03
I was refering to just those with soda ash, sorry.
Louis
>
>
> Louis Katz wrote:
>
> ...
> Shino glazes seem to go through a similar maturing over the course of
> a few days. Because solubility is related to temperature, sometimes
> glazes look different when applied at different temps. One shino in
> school seemed to be wilder in the winter. Most such changes must be
> very subtle or non existent as they evade detection.
>
>
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