Craig Martell on sun 26 mar 06
Jorge was asking:
>I try to make clear that Im trying to understand Why it turned RED,to
>replicate the firing
Hello Jorge:
I've refired iron glazes to 1988 F (cone 03) in the electric several
times. I use a couple of dark tenmoku glazes that are fired to cone 10
reduction and where the glaze is thinner I see red develop. On the other
parts of the pot where the glaze is applied thicker the color is usually a
yellow/green after the refire. So, I think maybe the red that you achieved
before was because of a thinner application of glaze.
regards and buena suerte, Craig Martell Hopewell, Oregon
Jorge Nabel on sun 26 mar 06
Clayarters, I already sent this post, but was advised to re send it
after NCECA-
I need some advice coming from experience.
After a Currie grid , we developed a bunch of Iron Saturate ^6 glazes
Electric (ox)
They range from caramel to metalic grey,to black. You know, the standard.
We refired some of them to bisque (1000C)and those closer to corner C
turned yellow.
Some changed from black to brown. But, in the only one firing we have
no records of,
when refired they turned a gorgeous RED. Of course it never happened again.
Since this happened, some months ago, I have read archives, hammer, some
other books
concernig iron cristals,etc,but couldnt duplicate the red.
Corner C is Nepheline, high alkaline frit and 20%dolomite. plus 15%RIO
Someone says it depends on fast first firing with enough heat, others
say go slowly up,
and so on.
I began to learn some chemistry in order to understand. But so far, no
clue.
Anyone has experienced this?
I try to make clear that Im trying to understand Why it turned RED,to
replicate the firing
Thanks, Jorge en Buenos Aires
Donna Kat on wed 29 mar 06
I quote from www.digitalfire.com because I can no longer get the link to work.
"Iron Red GB Glazes
Gerstley borate was used widely in bright red and maroon high iron glazes.
These contained as much as 25% iron oxide and many had more than 50% GB. The
red colors can be quite stunning (red is a very difficult color in
ceramics). Needless to say, they were very messy to work with. These glazes
are temperamental also, they have to be the right thickness (they run easily
and bubble/blister if applied too thickly, color does not develop if they
are too thin). Although it seems logical that they not be fired too quickly
to give the crystals time to grow, one respondent with 18 years of iron red
experience said this: "cone six firings require a medium fast fire to
maximum temperature in a vented kiln and the same for cooling. Venting
assures adequate oxidation. If maximum temperature is not reached or the
elements are going and it takes a much longer time to reach temperature the
color will be brown".
This is a glaze we use that works well when the firing is ramped to cool
slowly at about 1400. It also demands that Special Iron Oxide be used (if
any other iron oxide is used it is brown). This glaze tends to be redder on
the inside (where cooling is slower) than on the outside."
Toby's Red
earthy red
satin gloss opaque
6
small
segar
rich and lovely but uses gerstley
Gerstley Borate--1999 3200
Flint 3000
Feldspar--Kona F4 2000
Talc 1400
Kaolin--EPK 500
Iron Oxide--Red 1515
| |
|
