David Hendley on thu 11 may 06
I had great success with copper reds in my Cinco de Mayo
firing. Everything that had any copper in it was red through
and through.
I have about decided that very early reduction is the key. I
started reducing before I even had a dull red atmosphere.
This makes 2 firings in a row that seem to suggest this.
Here (below) is my red glaze. I formulated it to contain no
barium, strontium, or zinc, and it is well balanced for a
copper red (they are often low in alumina and sometimes
silica as well).
See my October 1999 Ceramics Monthly article for all the
specifics. This glaze will not run, as many copper reds are
prone to do. I fire to cone 10, with the tip of the cone
touching the shelf, but not melted flat.
See my website for some pictures from this firing:
www.farmpots.com/sale.htm
Simply Red, cone 10 reduction
Custer feldspar 45
Gerstley Borate 9
Whiting 12
Talc 6
Bentonite
EPK kaolin 3
Flint 22.5
Tin oxide 2
Copper carbonate .8
Unity formula
*CaO .54
*MgO .19
*K2O .16
*Na2O 10
B2O3 .12
AL2O3 .32
SiO2 3.42
Expansion 7.27
David Hendley
Maydelle, Texas
david(at)farmpots(dot)com
"EXTRUDE IT! Getting the Most From
Your Clay Extruder" available at
http://www.farmpots.com
Mark Issenberg on thu 11 may 06
Howdy David,, i have a question about the red firings.. Do you open your
kiln after cone 10 or do you close it up tight?
Im my Alpine i like to open my damper for 15 minutes before i close the kiln
down.. Im hoping that it lets any bubbles in my glaze to heal
Mark
David Hendley on fri 12 may 06
> Howdy David,, i have a question about the red firings.. Do you open your
> kiln after cone 10 or do you close it up tight?
> Im my Alpine i like to open my damper for 15 minutes before i close the
> kiln
> down.. Im hoping that it lets any bubbles in my glaze to heal
This is somewhat of a dilemma, Mark. I believe (can't prove
it, but it's what I think) that crash cooling for several hundred
degrees helps in the development of nice bright copper reds.
But.....it is not good for just about everything else. It is hard
on the kiln and the kiln furniture. It can encourage pinholing,
and I think it hinders the development of nice mat glaze surfaces.
So, I leave the kiln open for a few minutes while I work on the
coal beds in the fireboxes, then I close it up -- Cover on the top
of the stack and fireboxes closed.
In about 3 or 4 hours, I come back and close it up even tighter,
for the all important 1800 to 1400 degree cool down, with
little snakes of clay in cracks between the door bricks and
around the gaps in my damper.
David Hendley
Maydelle, Texas
david(at)farmpots(dot)com
"EXTRUDE IT! Getting the Most From
Your Clay Extruder" available at
http://www.farmpots.com
William & Susan Schran User on fri 12 may 06
Hey Dave - Assume the bentonite is 2.5?
-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu
On 5/11/06 5:54 PM, "David Hendley" wrote:
> Simply Red, cone 10 reduction
>
> Custer feldspar 45
> Gerstley Borate 9
> Whiting 12
> Talc 6
> Bentonite
> EPK kaolin 3
> Flint 22.5
> Tin oxide 2
> Copper carbonate .8
Bruce Girrell on fri 12 may 06
And that was on what type of clay, David?
That pink stuff that shows in a few places in your Serving Bowl - That's
what I get everywhere.
Bruce Girrell
in cool, windy northern Michigan
having yet to obtain a consistent copper red
even with Simply Red
Dan Dermer on fri 12 may 06
I think that getting good, consistent copper reds requires lots of variables
controlled, just like other types of glazes.
For reds:
- glaze thickness: a thicker application of glaze on white stoneware or
porcelain clay body makes a better red. thin spots in pots can mean less
glaze is applied which may mean less red. To be sure of a nice thick coat
on any pot, dip the first layer of copper red, then spray on the second
coat. I use two different copper red formulas for the two coats, which
helps get a deeper, more interesting red color.
- strong, early reduction (.75-78 on the oxy probe) starting at cone 011 or
010, held for around an hour. then start lightening up reduction bit by bit
as the kiln temp climbs. alternate between heavier and lighter reduction on
the way to cone 10.
- after shutting of the gas at the end of the firing, leave the damper open
for a minute or two, letting oxygen fill the kiln as it crash cools for a
little while. brighter reds, and glossier surfaces from the influx of
oxygen and crash cooling, respectively. Then seal up tight until your
re-lighting procedure...
- re-light the kiln at 1825-1850, and bring temp back up to 1900 or so over
the course of 30-45 minutes time (at most), then shut off again. The longer
cool-down and soak gives more surface crystals (in all glazes) and hare's
fure depth to the reds! yummy! Don't soak for too long, tho, as the
surface may get liverish or muddied, in my experience.
-Dan
www.higherfirestudios.com
David Hendley on fri 12 may 06
> And that was on what type of clay, David?
> That pink stuff that shows in a few places in your Serving Bowl - That's
> what I get everywhere.
Thanks for looking at the photos of my copper reds.
There really is no pink in any of these - I know what
you mean, but I didn't get any of it in this firing. It
must be light reflection that makes it appear pink.
I know that generally copper reds will tend to go pink
if they are underfired or have excess silica in the formula.
My "Simply Red" does tend to get some purple-ish
overtones. I think that is caused by the magnesium
and boron in the glaze.
I can live with this because both those elements are
low expansion oxides, which help to keep the glaze
from crazing.
The very brightest, reddest copper reds are overloaded
with potassium and/or sodium. They yield nice bright
colors, but they tend to run and craze. The popular
"Pete's Red" is in this category.
Simply Red is a glaze that even Ron Roy could use.
I use Blackjack stoneware clay. It is a fine-grained,
light brown clay which takes flame flashing nicely.
And, yes, I left the amount of bentonite out of the
recipe - sorry, it is 2.5, so the recipe adds up to 100.
>> Simply Red, cone 10 reduction
>>
>> Custer feldspar 45
>> Gerstley Borate 9
>> Whiting 12
>> Talc 6
>> Bentonite 2.5
>> EPK kaolin 3
>> Flint 22.5
>> Tin oxide 2
>> Copper carbonate .8
>
David Hendley
Maydelle, Texas
david(at)farmpots(dot)com
"EXTRUDE IT! Getting the Most From
Your Clay Extruder" available at
http://www.farmpots.com
BJ Clark | Stinking Desert Ceramics on fri 12 may 06
To all:
I use the following recipe from the archives.
Copper Red Cone 9-11 (from Walter Donald Kring)
Gerstley Borate 9.10
Whiting 14.27
Nepheline Syenite 44.26
Potash Feldspar 6.20
Kaolin 2.59
Flint 23.58
100.00%
Add:
Copper Carbonate 0.41%
Tin Oxide 1.04%
I use it on porcelian (mile hi jiki), b-mix, mile hi 48S (grey) and it come=
s
out red every time, on every part of the pot.
I use a downdraft kiln, home made, don't remember the cubic ft but it's 2
9in x 18in shelves.
Start reduction at 06, keep the same reduction the whole time, turn it off
at 10 touching the tip in the middle (hottest part of kiln).
no downfire, no crash cool, nothing crazy.
Comes out NICE every single time.
Here's a old pic of an old tea pot:
http://www.flickr.com/photos/robotdeathsquad/145258756/
My $.02
BJ Clark
Western Colorado
Just about to leave the house to coach my soccer team in their final game.
They all graduate from high school this weekend. Been a fun 4 years.
On 5/12/06, David Hendley wrote:
>
> > And that was on what type of clay, David?
> > That pink stuff that shows in a few places in your Serving Bowl - That'=
s
> > what I get everywhere.
>
> Thanks for looking at the photos of my copper reds.
> There really is no pink in any of these - I know what
> you mean, but I didn't get any of it in this firing. It
> must be light reflection that makes it appear pink.
> I know that generally copper reds will tend to go pink
> if they are underfired or have excess silica in the formula.
>
> My "Simply Red" does tend to get some purple-ish
> overtones. I think that is caused by the magnesium
> and boron in the glaze.
> I can live with this because both those elements are
> low expansion oxides, which help to keep the glaze
> from crazing.
> The very brightest, reddest copper reds are overloaded
> with potassium and/or sodium. They yield nice bright
> colors, but they tend to run and craze. The popular
> "Pete's Red" is in this category.
> Simply Red is a glaze that even Ron Roy could use.
>
> I use Blackjack stoneware clay. It is a fine-grained,
> light brown clay which takes flame flashing nicely.
> And, yes, I left the amount of bentonite out of the
> recipe - sorry, it is 2.5, so the recipe adds up to 100.
>
>
> >> Simply Red, cone 10 reduction
> >>
> >> Custer feldspar 45
> >> Gerstley Borate 9
> >> Whiting 12
> >> Talc 6
> >> Bentonite 2.5
> >> EPK kaolin 3
> >> Flint 22.5
> >> Tin oxide 2
> >> Copper carbonate .8
> >
>
>
>
> David Hendley
> Maydelle, Texas
> david(at)farmpots(dot)com
>
> "EXTRUDE IT! Getting the Most From
> Your Clay Extruder" available at
> http://www.farmpots.com
>
>
> _________________________________________________________________________=
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>
--=20
BJ Clark
Stinking Desert Ceramics
bjclark@stinkingdesert.com
www.stinkingdesert.com
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