Ron Roy on thu 6 mar 03
Hi Annapoorna,
Potash spars are usually the best from cone 6 up - Sodium starts to
vaporize at about that temperature and shortens the life of bricks and
shelves.
It is going to be hard to get the right amount of melt at cone 6 to vitrify
white bodies - if there is enough low fire red clay involved spar will do
it.
The white bodies need some thing extra - like neph sy or talc.
Neph sy will eflocculate clay so you need to add some Epsom salts to
counter it - very little 0.2 percent well disolved.
RR
>hello
>
>I am new at pottery.So new that I am just realising what an chasim the
>uninformed potter has to delve.Especially as we are in India and we have
>to make our own clay bodies glazes etc.
>
>A friend and I are testing clay bodies and after a couple of firings we
>are planning on standardise our body .In this process we are wondering
>which is a better feldspar for a midfire stoneware body to use a-- potash
>feldspar or a soda feldspar.
>
>We have been testing on mainly soda feldspar based clay bodies.Eventually
>we will only be using potash feldspar. So will all our previous results
>with the soda based feldspar have no bearing on the potash feldspar based
>clay body.
>
>Sorry for the longwinded mail.I have a lot more questions to ask but will
>keep it for later.
>
>annapoorna
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
=?iso-8859-1?q?Annapoorna=20Sitaram?= on thu 6 mar 03
hello
I am new at pottery.So new that I am just realising what an chasim the uninformed potter has to delve.Especially as we are in India and we have to make our own clay bodies glazes etc.
A friend and I are testing clay bodies and after a couple of firings we are planning on standardise our body .In this process we are wondering which is a better feldspar for a midfire stoneware body to use a-- potash feldspar or a soda feldspar.
We have been testing on mainly soda feldspar based clay bodies.Eventually we will only be using potash feldspar. So will all our previous results with the soda based feldspar have no bearing on the potash feldspar based clay body.
Sorry for the longwinded mail.I have a lot more questions to ask but will keep it for later.
annapoorna
Catch all the cricket action. Download Yahoo! Score tracker
David Beumee on fri 7 mar 03
Annapoorna,
Are you after a cone 6 stoneware that fires more on the whiter side
or on the red to brown side?
As Ron has said, low fire red clays will go a long way to help your spar flux the body
properly, and it's true that sodium based feldspars are alot more useful at cone 6 than
potash based spars because their fluxing action is by nature stronger,
so if it's possible, stay with the sodium based spar you
began with for best results. Ron is also correct about some deflocculation of the
clay occuring with the use of sodium based feldspars such as nepheline
syenite, an action that will make your clay flabby and unable to stand properly
as you throw it on the wheel. 0.2 - 0.4% either epsom salts or calcium chloride
added to your body tests will greatly counteract deflocculation. Add the percentage
of either to water and allow to dissolve before adding to the water in which you mix your
clay body tests.
If you want a cone six white stoneware and frits are available, I have used
small percentages of Ferro frit 3195 to help flux a cone 6 body.
Please continue your questions on or off line if you need help.
David Beumee
Earth Alchemy Pottery
Lafayette, CO USA
3/5/03 6:05:10 PM, Annapoorna Sitaram wrote:
>hello
>
>I am new at pottery.So new that I am just realising what an chasim the uninformed potter has to
delve.Especially as we are in India and we have to make our own clay bodies glazes etc.
>
>A friend and I are testing clay bodies and after a couple of firings we are planning on standardise our body
.In this process we are wondering which is a better feldspar for a midfire stoneware body to use a-- potash
feldspar or a soda feldspar.
>
>We have been testing on mainly soda feldspar based clay bodies.Eventually we will only be using potash
feldspar. So will all our previous results with the soda based feldspar have no bearing on the potash
feldspar based clay body.
>
>Sorry for the longwinded mail.I have a lot more questions to ask but will keep it for later.
>
>annapoorna
>
>
>
>Catch all the cricket action. Download Yahoo! Score tracker
>
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