Changes in G200 Type Feldspar Information
Since 2009, when the feldspar mine was depleted of the traditional G-200 potash feldspar, the ceramics industry has been constantly adjusting. In the last two years there have been more significant changes. The Monticello, GA (G-200HP) mine has closed and recently the Pacer Corporation has experienced some challenging production issues.
Effective immediately, because of a broken ball mill, the Pacer Corporation was forced to stop production of 200 mesh Custer feldspar. The Pacer Corp. will now only produce 325 mesh Custer.
These latest changes have not given the industry a lot of time to adjust, but fortunately there is another potash feldspar available. G200EU is mined in Spain and has proven to be a quality potash feldspar.
That being said, we cannot stress enough the importance of testing your clay in your own studio situation. What works for one potter may not work for all. There will undoubtedly be adjustments in certain situations. Sheffield Pottery has an inventory of clays made with 200 mesh Custer feldspar, but will immediately start the transition to G200EU in our stock clay bodies. We will also inventory 325 mesh Custer for those who would like to use it in custom formulas and glazes.
Below is a side by side comparison of the old and new available Feldspars.
|
|
Old G-200 |
G-200 HP |
G-200HP Minspar Blend |
CusterFeldspar |
G-200 EU |
|
SiO2 |
66.3 |
66.0 |
66.8 |
68.5 |
68.5 |
|
Al2O3 |
18.5 |
18.3 |
18.2 |
17.0 |
17.0 |
|
Fe2O3 |
.08 |
.09 |
.08 |
.10 |
.095 |
|
K2O |
10.8 |
14.2 |
11.17 |
10.0 |
11.0 |
|
Na2O |
3.1 |
.09 |
2.0 |
3.0 |
2.1 |
|
CaO |
.80 |
.30 |
.66 |
.30 |
.05 |
|
MgO |
trace |
trace |
trace |
trace |
.08 |
|
LOI |
.15 |
.15 |
.20 |
.30 |
.05 |
Below is a list of our stock clay bodies affected by this change: 45R, 3350, 20231G, 20231NG, 20266, 92700, 95400G, 95400NG, 108200, 108300, 108950, 110100, S14, T1NS, T1S, T3,T3S, T360, W1A