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crystals in glaze

updated mon 24 nov 97


wallace myers on wed 12 feb 97

I recently purchased a Duncan glaze called Crystaltone Glaze, it has
crystals in the bottom of the container that are supposed to melt during
firing and give a mottled or variegated effect. My question is, can I
purchase the crystals and put them in my own glaze?

Eleanora Eden on fri 14 feb 97

Hi Wallace and All,

Awhile back I bought some little packets of such crystals in red and in
white from my supplier which is also a supplier of hobby ceramics stuff.
I used them afew times so I know they work.


Eleanora Eden 802 869-2003
Paradise Hill
Bellows Falls, VT 05101

[the address is temporary. My mailbox at still works -- do not change address books]

George Mackie on sun 23 nov 97

Terri- 0.5% epsom salts (magnesium sulphate) was recommended to me by John
Conrad of San Diego Mesa College. He puts it in all his glazes and never
gets crystals. However its primary function in a glaze is probably to
thicken the glaze up and make it easier to get a good coat of glaze on
less absorbent surfaces. Another approach to crystals might be to acidify
the glaze slightly with vinegar at about 1% by volume You would do this
while making it up, not as a way of getting rid of crystals once formed (
same with epsom salts).
Conrad told me that he never makes up high lithium glazes until ready to
use them as crystals form if they are left to sit around. Ive forgotten
how much Li you have in yours but I would say 8% would be "high". I
like lithium for the wonderful colours it gives with copper in low fire
oxidation glazes but it does seem to be tricky stuff. George

On Fri, 21 Nov 1997, Terri Storer wrote:

> George,
> Thanks for the reply. I also have other glazes with lithium carb or
> gerstley borate but not both. I haven't noticed the problem with them.
> How much epsom salt do recommend?
> Thanks again!
> Terri Storer