Pamela Watkins on thu 4 mar 04
Hello all,
Spodumene...... can someone tell me what roll this chem plays, what is it? Is there a recommended substitue?
The Glaze Book gives descriptions and purpose of
some of the main glaze ingredients, but this one is not
listed. I've had no luck in other books I've consulted, and will be
purchasing the RR/John Mastering book in Indy, so at this time I
don't know if it is described there, so I thought I'd ask.
And, Soda Spar.......If a glaze call for this, can soda ash or some other form of sodium be used in a relative quantity to a standard Feldspar?
TIA,
Peace,
Pamela
~jaq
---------------------------------
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daniel on thu 4 mar 04
Hi Pamela,
> Spodumene...... can someone tell me what roll this chem plays, what is it? Is there a recommended substitue?
Its a lithium feldspar. Check out http://digitalfire.com/oxide/li2o.htm for
more details. I've never used it - hopefully someone who has can give you
some experiential info.
Thanx
D
David Hewitt on fri 5 mar 04
Pamela,
The generic analysis of Spodumene is LiO2 1, Al2O3 1, SiO2 4
You can therefore substitute Lithium Carbonate, Kaolin and Silica or
Lithium Carbonate, Alumina Hydrate and Silica.
You can see actual analysis as used by Bath Potters on their web site or
mine under Bath Potters' Supplies Raw Material Data
http://www.dhpot.demon.co.uk
I would think that the reference in a recipe to Soda Spa means Soda
Feldspar. An analysis is also shown on the reference above
David
In message , Pamela Watkins writes
>Hello all,
>
>Spodumene...... can someone tell me what roll this chem plays, what is it? Is
>there a recommended substitue?
>The Glaze Book gives descriptions and purpose of
>some of the main glaze ingredients, but this one is not
>listed. I've had no luck in other books I've consulted, and will be
>purchasing the RR/John Mastering book in Indy, so at this time I
>don't know if it is described there, so I thought I'd ask.
>
>
>And, Soda Spar.......If a glaze call for this, can soda ash or some other form
>of sodium be used in a relative quantity to a standard Feldspar?
>TIA,
>
>Peace,
>Pamela
>~jaq
>
>
>
>---------------------------------
>Do you Yahoo!?
>Yahoo! Search - Find what you’re looking for faster.
--
David Hewitt
David Hewitt Pottery
South Wales UK
Web:- http://www.dhpot.demon.co.uk
Ivor and Olive Lewis on fri 5 mar 04
Dear Pamela,
Spodumene is a Lithium bearing Felspar. Other similar compounds are
Petalite and Lepidolite. Lithium can also be supplied by using Lithium
Carbonate, which is a soluble material and has other drawbacks .(See
the Archives on this one, copious notes there)
If you have a glaze calc program you can fiddle the numbers to sub
what is available for Spodumene in a glaze but do not expect identical
fired results.
Two main uses. 1 Adjustment of Coef of Exp; 2 Colour modification
I prefer Petalite. Pay about $Au350 a bag for it.
Soda Felspar can cause problems because of the adverse influence on
Coef of Exp. but I prefere it to K-Felspars since it can mimic the
optical qualities of Lead glazes with brilliant reflections. I temper
its adverse influence with Petalite. I would not think of substituting
Soda Ash for a felspar. Ababi uses Cryolite, an insoluble source of
Sodium, successfully in some of his glazes
Plenty of info if you search for it.
Best regards,
Ivor Lewis. Redhill, South Australia
Lee love on fri 5 mar 04
Pamela Watkins wrote:
Hi Pamela, where do you live?
>listed. I've had no luck in other books I've consulted, and will be
>purchasing the RR/John Mastering book in Indy, so at this time I
>don't know if it is described there, so I thought I'd ask.
>
>
Someone else explained what it is, but If you live where you
can't get spodumene, you might look at Glazechem http://glazechem.com/
You can try it for free for several months and then only pay $35.00
if you like it and want to keep using it.
In the materials substitution list, under Edouard Bastarache, there
are 6 substitution for Spodumene. Some of the subs are lithium
carbonate, kaolin and silica, the others use petalite.
>
>And, Soda Spar.......If a glaze call for this, can soda ash or some other form of sodium be used in a relative quantity to a standard Feldspar?
>
>
Back home, I usually used Kona F4. If you tell us where you
live it might be possible for folks to tell you what to look for.
Clazechem has 10 substitutions for Kona F4. This is a soda spar and in
the substitutions you find whiting used to adjust other feldspars.
Good luck!
Lee In Mashiko
Lee@Mashiko.org
http://Mashiko.us
"With Humans it's what's here (he points to his heart) that makes
the difference. If you don't have it in the heart, nothing you make will
make a difference." ~~Bernard Leach~~ (As told to Dean Schwarz)
Ron Roy on sat 6 mar 04
Hi Pamela,
As others have said - it's like a spar but - a spar supplies sodium and
potassium (KNaO) while spodumene supplies lithium.
Lithium is very much like sodium and potassium - a low temperature alkaline
flux. The big diff is sodium and potassium have a high expansion - the
highest of all the oxides we use - while lithium has quite a low expansion.
If you sub in a spar for spodumene you will probably get crazing. Maybe not
- it's worth a test.
Because spars and spodumenes differ from mine to mine it is probably best
to do it using calculation software and actual typical analysis for the
materials you are using - if you want the glazes to look the same. I will
save a lot of testing and time.
The alkalies do have somewhat different colour responses to certain
colouring oxides but for a whit glaze it will not mater.
RR
>Spodumene...... can someone tell me what roll this chem plays, what is it?
>Is there a recommended substitue?
>The Glaze Book gives descriptions and purpose of
>some of the main glaze ingredients, but this one is not
>listed. I've had no luck in other books I've consulted, and will be
>purchasing the RR/John Mastering book in Indy, so at this time I
>don't know if it is described there, so I thought I'd ask.
>
>
>And, Soda Spar.......If a glaze call for this, can soda ash or some other
>form of sodium be used in a relative quantity to a standard Feldspar?
>TIA,
>
>Peace,
>Pamela
>~jaq
>
>
>
>---------------------------------
>Do you Yahoo!?
>Yahoo! Search - Find what you=EDre looking for faster.
>
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Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
=46ax: 613-475-3513=20
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