Chris Schafale on thu 6 may 99
For those who are interested, here are a couple of
"works-in-progress" glazes to try, and a glaze development story to
go with them. First the story (scroll down now if you just want the
recipes):
Last fall, in my new-to-glaze-chemistry innocence, I
decided to try my hand at getting an iron red glaze for cone 6
oxidation. I gathered recipes, searched the archives, and mixed up
about 8 different glazes, with names like "Tomato Red", "Ketchup
Red", etc. I fired them fast, fired them slow, fired them with long
cooling periods, fired them again to bisque temperatures. All of
them turned out various shades of brown, with, at most, hints of red.
A couple of them I liked as brown, so I set them aside for further
testing. The rest, with a sigh, I dumped into one bucket, and
labelled it "Iron Mystery Glaze".
One day I decided to do fire a test of "Iron Mystery" just
for fun. It came out brown, but with intriguing amounts of red
crystals sprinkled over the surface, and with a surprisingly nice
gloss texture (all the component glazes were matt). I refired the
test to 04, and voila -- red! Cool, but wouldn't it be nice if it
came out red on the first try...
In the meantime, I had developed a red glaze of my own, which I
posted under the name "Chris Red" -- it's red all right, but kind of
a dull, dry matt surface. Wouldn't it be nice if it had some of the
gloss of the "Iron Mystery Glaze"....
Line blend time. And to cut to the chase, the 60-40 and 80-20 blends
of "Iron Mystery" and "Chris Red" tested out really quite nice. IMCR
6040 is a deep rust to burgundy color, depending on the light, and
the texture is a lovely caressable satin matt. IMCR 80-20 has a bit
more rusty-orangey tone and breaks goldish-brown to black, surface is
more glossy. This is on various tan to brown stoneware clays -- I
haven't tried them on white clays.
I've been firing them along with loads of Floating Blue, so really
cone 5 rather than cone 6, and without really any extended cooling
(though I do turn off the vent once cooling has begun). If anyone
wants it, I'll gladly supply the exact firing schedule I'm using. So
far, in my kiln, the red color has been totally reliable, with no
instances of pieces coming out brown if fired in cooler or hotter
areas of the kiln. Also, at least with IMCR 6040 (which I've used
a lot more), the color has not been too sensitive to thickness -- if
it's really, really thick, it might go slightly gold, but mostly
thicker areas are just a bit more matt. I have a sense that IMCR
8020 (which I just mixed a larger batch of and started using) might
be more sensitive (and give more variety over texture, etc.)
So, in hopes that some of you will try them out and let me know what
happens, here are the recipes. You will notice that the amounts are
weird, and that there are lots of ingredients -- this is the result
of mixing 7 different glazes together and then trying to figure out
what's in the bucket. I suspect that the recipes could be
simplified, but I haven't had time to do that testing yet, and I
couldn't wait to share the early results. I have not done complete
durability testing, but preliminary results look good. Haven't sent
it off to Alfred for testing either, but the good news is, there's
nothing bad in here to leach out! As always, test, test, test, your
mileage may vary, etc. Happy glazing, and please do post results.
I'd love to know if these will hold up with other people's kilns,
materials, etc.
Chris Schafale
__________________________________
IMCR 6040 (Burgundy Satin)
==============================
EPK KAOLIN.......... 4.25
KT 1-4 BALL CLAY.... 5.90
SILICA.............. 31.60
GERSTLEY BORATE .. 16.00
G 200 FELDSPAR...... 4.50
CUSTER FELDSPAR..... 2.00
F-4 FELDSPAR........ 11.50
TALC................ 9.00
DOLOMITE............ 7.75
WHITING............. 0.90
BONE ASH............ 6.60
SPANISH RED IRON OX. 13.00
========
113.00
CaO 0.50* 10.51%
MgO 0.38* 5.76%
K2O 0.04* 1.51%
Na2O 0.08* 1.88%
TiO2 0.00 0.12%
Al2O3 0.21 7.89%
B2O3 0.21 5.51%
P2O5 0.06 3.37%
SiO2 2.79 63.12%
Fe2O3 0.01 0.33%
Si:Al 13.57
SiB:Al 14.60
Expan 5.87
IMCR 8020 (Glossy Rust)
================
EPK KAOLIN.......... 6.00
KT 1-4 BALL CLAY.... 4.00
SILICA.............. 31.00
GERSTLEY BORATE .. 17.50
G 200 FELDSPAR...... 2.50
CUSTER FELDSPAR..... 3.00
F-4 FELDSPAR........ 15.50
TALC................ 8.00
DOLOMITE............ 6.50
WHITING............. 1.00
BONE ASH............ 5.00
*IRON OXIDE RED...... 13.00
========
113.00
CaO 0.49* 9.53%
MgO 0.36* 5.12%
K2O 0.05* 1.58%
Na2O 0.10* 2.21%
TiO2 0.00 0.10%
Al2O3 0.25 8.73%
B2O3 0.25 6.02%
P2O5 0.05 2.56%
SiO2 3.04 63.81%
Fe2O3 0.01 0.35%
Si:Al 12.40
SiB:Al 13.41
Expan 5.95
Light One Candle Pottery
Fuquay-Varina, NC
candle@intrex.net
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