Molly Forman on thu 23 jan 97
Greetings, all --
A computerless friend has asked me to forward a question about a glaze
curiosity. She has been mixing the same spodumene glaze for many years.
The last several batches have been loaded with vast numbers of little bubbles
when freshly mixed. Some of these bubbles disappear when the bucket sits
for several days, but not all of them. Stirring creates new bubbles, though no
as many as at first. Firing performance does not seem particularly affected,
but there are a lot of pinholes to be rubbed smooth before firing. This is the
only glaze in the studio behaving this way.
(I did ask if she?d purchased new chemicals in that time, thinking about recent
changes in spodumene. She said that she was pretty certain that the spod
was the same batch that she?s had for quite a while, but that the spar, whiting,
or EPK could well be new.)
Can anyone enlighten us as to what could be reacting with what?
The formula (for Alfred Spodumene glaze) is:
Soda Spar (originally Oxford feldspar) 30
Spodumene 20
EPK 25
Whiting 5
Dolomite 20
____________________________________
Tin Oxide 6
TIA
--Molly
Molly Forman
mforman@crs.loc.gov
PJLewing@aol.com on fri 24 jan 97
Molly,
This is a thread that was discussed at length a few months back on Clayart.
It's too bad you missed it.
As I recall, there were several explanations as to what causes this problem
in some batches of spodumene, but I do know from experience that there are
two things you can do to fix it. You can calcine the spodumene, or you can
mix it up a few days before you'll need it with LOTS of water, let it settle,
and siphon the water off. Add more water, stir, and repeat. Two or three
changes of water will eliminate whatever soluble substance is causing the
problem.
PAul Lewing, Seattle
Bill Amsterlaw on sat 25 jan 97
Molly Forman wrote on 23 Jan 1997:
>>
A computerless friend has asked me to forward a question about a glaze
curiosity. She has been mixing the same spodumene glaze for many years. The
last several batches have been loaded with vast numbers of little bubbles when
freshly mixed.
<<
This phenomenon has been discussed on Clayart in the past. The best
explanation came from Bob Burruss 10 Mar 1996 who wrote:
>>
Spodumene is mined from pegmatites where it occurs with a variety of other
minerals like petalite, quartz, and feldspars. During mining, the spodumene
and other minerals are ground and must be separated and purified. The most
common purification method is floatation in an air/water mix to separate the
minerals by density. Normally a surfactant (soap) is added to aid the
separation. I'm guessing that the ceramic grade spodumene may still have
traces of soap in it and that causes the foaming. The fact the person who
started this thread (sorry, can't remember your name) said that the foaming
went away after calcining the spodumene suggests that the soap was burned out.
<<
Two different methods were offered for getting rid of the foam by Paul Lewing
. On 6 Mar 1996, he wrote:
>>
I have a batch of spodumene that produces this same kind of bubbles. I've had
it for years, and have asked many people about the problem, but you're the
first person other than I who has said they've seen this.
I discovered two solutions:
1) One was to calcine the spodumene. This didn't seem to affect how much
weight of the material was needed- 50 g of calcined seemed to produce the same
result as 50g of raw.
2) The other solution, which I usually used, was to mix the glaze up several
days before it was needed with LOTS of water, stir well, let settle overnight,
and siphon off all the water. Add more water. Do this two or three times, and
the bubbles will be gone.
<<
The observation was made that the spodumene now being sold by most suppliers
is whiter than the way spodumene used to look. This white spodumene is mined
in Australia and does not have a tendency to foam like the older blue-gray
material.
An explanation of the change in supply was offered by COOPJ@aol.com on 25 Nov
1996:
>>
Yes, indeed the Spodumene sources have changed again. Foote Chemical used to
be the major supplier of Lithium materials in the USA. Foote quit supplying
Spodumene about a year or two ago. Most suppliers are now selling Australian
Spodumene. The Foote Spodumene was higher in iron oxide and so could account
for the color difference. I think you will find that the Australian material
is probably purer than the older material and may fire whiter. If this is
objectionable you can add some iron oxide to it. Some of us "old timers" used
to buy the lower iron Ceramic Grade Spodumene from Foote in the early 1980's
and sreamed when they started selling the higher iron grade. The Australian
material is actually more like the good old stuff. I guess every thing works
in cycles even Ceramic chemicals.
<<
On 27 Nov 1996 Richard Burkett
commented that chemical analyses of spodumene from several sources is
available on the CeramicsWeb .
- Bill Amsterlaw (wamster@msn.com)
Plattsburgh, NY
Margaret Arial on sun 26 jan 97
This old timer had such a large supply of spodumene ,at .07 per pound in
quantity, and was out ot lunch when all the changes came about that i ordered
100 pounds without asking rhe price and was thrown for a loop when my price
came back at over $1OO! Won't make that mistake again.What is the price
roughly for this version that's like the old Foote version and is it widely
available?
Don Goodrich on tue 28 jan 97
Margaret,
Just checked my supplier's catalog: $50.00 for a 100-lb bag of spodumene.
This is from Great Lakes Clay Supply in Illinois. The spod in the last batch
I bought (last October) is white, and does NOT bubble in water. For what
it's worth...
Don Goodrich getting bored with snow in Zion, Illinois
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