Marianne Cordyack on wed 2 feb 05
Last winter I had several glazes (all contained lithium) develop
crystals. Some were tiny, others the size of quarters - all beautiful!
I thought the glaze was probably ruined. I tested several of them and
the crystals produced shiny spots in the fired surface - actually not
very pleasing. The glaze itself was also a bit more matte. However, I
decided to experiment. I sieved the glazes to remove the crystals,
added water to them, then heated them in the microwave just until the
water got very hot, but not boiling. The crystals melted! I poured
the solutions back into the glazes and tested them again. The glazes
worked just like they always had! No need to add buckets of glaze to
Jonathan Kirkendall on thu 3 feb 05
I had the same thing happen to my cone 6 Falls Creek Shino - did the
same thing, melted down the crystals and added back the water. I
believe, though it's been quite a few years, that someone posted to this
list that the crystals were lithium borate? The glaze had both lithium
and Gerstley Borate in it. Anyway, not altogether too troublesome, but
I must say I never thought the glaze looked quite as good after melting
down the crystals and adding them back, as it did before, but still usable.
Jonathan in DC
where it's snowing, for crying out loud. Who knew?
Marianne Cordyack wrote:
> Last winter I had several glazes (all contained lithium) develop
> crystals. Some were tiny, others the size of quarters - all beautiful!
> I thought the glaze was probably ruined. I tested several of them and
> the crystals produced shiny spots in the fired surface - actually not
> very pleasing. The glaze itself was also a bit more matte. However, I
> decided to experiment. I sieved the glazes to remove the crystals,
> added water to them, then heated them in the microwave just until the
> water got very hot, but not boiling. The crystals melted! I poured
> the solutions back into the glazes and tested them again. The glazes
> worked just like they always had! No need to add buckets of glaze to
> the landfill.
> Marianne Cordyack
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John Britt on sat 2 jul 05
Just wanted to let you know I have an article that you may be interested
in on the website: Ceramics Today.
It is on the crystals that form in the glaze bucket. This has been
repeatedly talked about on Clayart and so I wrote an article that was
published in Ceramics Review in January/February 2005.
Hope you like it. Steve has a great site which is a wonderful resource
for ceramicists around the world!
Check it out,
Laurie on thu 7 jul 05
What a nice article. You explain things very clearly and the
illustrations are very nice to look at.
I was one of those "what are these crystals in my lavender glaze bucket
from?" people. They were in a bucket of Tom Coleman's Lipstick Purple
glaze that had been sitting out in my garage over the winter months. It
doesn't get super cold out there, but the temps average in the 40's and
low 50's for a few weeks. I guess that was cool enough to get the
crystals. I did like you and fired pots dipped in the Lipstick Purple
and with some of the larger crystals strategically placed on them to
see what they would do. Some effects were so-so, but a couple of them
were quite nice.
Thanks for showing me what was going on!
Potters Council, charter member
Sacramento Potters Group, Secretary
Paul Herman on thu 7 jul 05
Hi John Britt,
Thank you for the interesting article on those little floating crystals.
I've experienced them in a couple of glazes in wintertime. They went
away when I got radiant floor heat, and haven't come back.
Great Basin Pottery
Doyle, California US
>From: John Britt
>Subject: Re: Crystals in the glaze bucket
>Date: Sat, Jul 2, 2005, 6:54 AM
> Hello all,
> Just wanted to let you know I have an article that you may be interested
> in on the website: Ceramics Today.
> It is on the crystals that form in the glaze bucket.
John Britt on thu 7 jul 05
Glad you liked it! I have heard this discussed many times on Clayart and
so thought I should work up an article.
Actually, I am thinking of getting a line of glazes by growing the
crystals. I guesss I should rethink the radiant floor heat!
John Britt on fri 8 jul 05
My pleasure. It was really fun to see all the different crystals and then
try to grow them. It happens in many types of glazes from Raku to high
fire. And, as yo ufound, the temperature doesn't have to be freezing -
justlow enough to precipitate out the soluble material.
Hope it helps,