iandol on fri 14 dec 01
Dear Judith I. Marvin,
Looking at your recipe:
Cushing Satin Matt: 20% Whiting, 25 Frit 3134, 25 Neph Sy, 15 EPK, 15 =
Silica, add 10% Zircopax;
It is important to think about what is causing the high expansion value =
in your glaze. Sodium is the most notorious element which adds to the =
value of this property and that is a component in Nepheline Syenite. =
Although I do not have an analysis of the frit, 3134 I suspect that this =
is also a source of sodium since it is listed by Chappell as being most =
useful in the cone 06-04 range.
So, in my opinion, the best way to retain the qualities of the glaze =
substitute a felspar which has a very low sodium content but an =
increased potassium content and replace Frit 3134 with one which has a =
higher melting value.
Another point to consider is why this glaze is a satin matt. This =
quality comes from the growth of micro crystals of Calcium Silicate, =
which would be expected from a recipe with such a high quantity of =
whiting. Reducing this by a significant degree may detract form the =
surface you are trying to achieve Zircopax may enhance the matt effect =
by the added opacity. If this is omitted your glaze may show greater =
luminosity.
Have fun experimenting.
Best regards,
Ivor Lewis. Redhill, South Australia
| |
|
