Paul on mon 29 jul 02
I have heard some say that G200 and Custer feldspar are substitutes for one
another, but then others have said that g200 has a lower melting point. for
this reason, i am planning to do some tests with the g200 because, if it
really does have a lower melting point, it will be helpful for some the the
glazes i use. Also, it is considerably less expensive where i live, for some
reason.
Does anyone know for a fact if these two feldspars are similar enough to be
used as substitutes; or is it true that the g200 does have a lower melting
point?
-Paul
Ron Roy on tue 30 jul 02
Hi Paul,
I can't tell if G200 is slightly more or less a melter than Custer by
looking at the molecular formula - Why not fire some of each on a tile and
see for your self - make a marbel - water will work - spit works better -
one of each - same size and fire them to cone 10 and you will see.
They are both potash spars - Custer has more silica than G200 and G200 has
a little more alumina.
You will not see the difference in most glazes - the more spar in the glaze
the bigger the diff will be.
The best way to do this is to substitute on a molecular level - that way
you can adjust for any differences.
RR
>I have heard some say that G200 and Custer feldspar are substitutes for one
>another, but then others have said that g200 has a lower melting point. for
>this reason, i am planning to do some tests with the g200 because, if it
>really does have a lower melting point, it will be helpful for some the the
>glazes i use. Also, it is considerably less expensive where i live, for some
>reason.
>Does anyone know for a fact if these two feldspars are similar enough to be
>used as substitutes; or is it true that the g200 does have a lower melting
>point?
>-Paul
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ruth Ballou on tue 30 jul 02
G-200 does melt a bit better than Custer. You would see this if you did
melt tests of each ingredient alone. However, at ^10, there is generally
little difference in the finished product, depending on the amount of spar
in the glaze, measuring variations that may occur during mixing, and
temperature and heating/cooling rate variations that may occur in the
firing. I've subbed one feldspar for the other many times with no
appreciable differences. If you're not quite satisfied with the degree of
melt in a glaze, I don't think exchanging g-200 for Custer is the solution.
Ruth Ballou
Silver Spring, MD
>I have heard some say that G200 and Custer feldspar are substitutes for one
>another, but then others have said that g200 has a lower melting point. for
>this reason, i am planning to do some tests with the g200 because, if it
>really does have a lower melting point, it will be helpful for some the the
>glazes i use. Also, it is considerably less expensive where i live, for some
>reason.
>Does anyone know for a fact if these two feldspars are similar enough to be
>used as substitutes; or is it true that the g200 does have a lower melting
>point?
>-Paul
>
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