Jay Gertz on thu 31 mar 05
I would like to take my favorite cone 10 reduction glaze and try and lower
it to a cone 5-6 oxidation, retaining it's color, which breaks from a brick
red (where thin) to a gray (where thick). Is this possible? I would think
the fact that one is reduction and the other oxidation would make this
impossible, retaining the same color characteristics that is. One text
mentions to change it from a batch formula to a molecular unity formula. I
am at a loss to know where to find the molecular weights for the elements in
the glaze formula. Any suggestions?
The formula (recipe) is
Nepheline syenite 61.49
Ball Clay 3.9
Tin Oxide 2.93
Copper Carb. 1.42
jay s. gertz
Paul Lewing on thu 31 mar 05
on 3/31/05 2:17 PM, Jay Gertz at jgertz@BULLDOG.UNCA.EDU wrote:
> I would like to take my favorite cone 10 reduction glaze and try and lower
> it to a cone 5-6 oxidation, retaining it's color, which breaks from a brick
> red (where thin) to a gray (where thick). Is this possible?
In a word, no. There is, as you say, the problem of going from reduction to
oxidation. And if there's one color that is supremely difficult to get in
mid-range oxidation, it's a bright iron red.
The other problem is with the base glaze. The general procedure when
lowering the firing temperature of a glaze is to keep the flux balance
exactly the same, while lowering both the alumina and the silica,
maintaining the same Si:Al ratio as in the original. The problem with
almost all highfire glazes, and this one more than most, is that there's
hardly any alumina or silica to start with. You could take it all out (and
in the case of this glaze all you could do would be leave out the ball clay,
which would make it settle like a rock with all that neph sy) and it
wouldn't be enough. You'd have to add significant amounts of secondary flux
or boron just to get it to melt, and then it wouldn't be the same glaze,
Paul Lewing, Seattle
Angela Davis on thu 31 mar 05
Use a glaze program to convert your recipe, I use
Glazemaster. A free trial program can be downloaded at John Hesselberth's
site at the following link. Very intuitive.
Who wishes she knew more about what to do once the
molecular weights are figured.
----- Original Message -----
From: "Jay Gertz"
Sent: Thursday, March 31, 2005 5:17 PM
Subject: Kottler's Cone 10 to Cone 5-6
> mentions to change it from a batch formula to a molecular unity formula.
> am at a loss to know where to find the molecular weights for the elements
> the glaze formula. Any suggestions?