Bob Johnson on sat 29 jan 11
I've been prowling the archives, but I don't see an answer to the two
questions below concerning copper reds. Can any of you glaze experts help
me?
1. If properly fired in reduction, will any copper glaze produce red
(or something in that part of the spectrum)? (I did see that iron tends to
make copper reds muddy.)
2. Has anyone experimented with wood ash in a copper red glaze?
Thanks!
Bob
Roseburg, Oregon
David Finkelnburg on sun 30 jan 11
Bob,
Copper reds are almost entirely achieved in the firing. Most
glossy glazes with 0.7 moles CaO and copper as a colorant have enough iron
to let the copper go to some shade of red if the copper is reduced before
the glaze melts and seals over.
Glazes intended as copper reds tend to give brighter reds, though.
Good glazing,
Dave Finkelnburg
http://www.mattanddavesclays.com
-----------------------------
Date: Sat, 29 Jan 2011 21:14:32 -0800
From: Bob Johnson
If properly fired in reduction, will any copper glaze produce red
(or something in that part of the spectrum)? (I did see that iron tends to
make copper reds muddy.)
Edouard Bastarache on sun 30 jan 11
"Has anyone experimented with wood ash in a copper red glaze?"
Check out this :
http://www.flickr.com/photos/potier/158073954/
I did that to try to mimick wood firing somehow
Gis,
Edouard Bastarache
Spertesperantisto
Sorel-Tracy
Quebec
http://www.flickr.com/photos/30058682@N00/
http://edouardbastarache.blogspot.com/
http://www.facebook.com/edouard.bastarache
http://bastaracheblogsarts.blogspot.com/
William & Susan Schran User on sun 30 jan 11
On 1/30/11 12:14 AM, "Bob Johnson" wrote:
> 1. If properly fired in reduction, will any copper glaze produce re=
d
> (or something in that part of the spectrum)? (I did see that iron tends t=
o
> make copper reds muddy.)
> 2. Has anyone experimented with wood ash in a copper red glaze?
Question #1 - Yes, but not reliably.
We have a dark transparent copper green that will turn red in spots if
reduced too heavy during early stages of firing.
Also used a copper turquoise mat that would also develop blushes of red.
Question #2 - No, haven't tested woodash in copper glazes.
Why not start with a copper red glaze and begin adding 5% increments of
woodash to test the effect. I would expect the glaze to become more fluid.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Lee on sun 30 jan 11
Bob,
You want low alkali low alumina for best copper reds.
Oxides - Cu2O
Copper is well-known for its ability to produce blood-red and fire-red
colors in steady reduction atmosphere firings where CuO is altered to
Cu2O. Bright red colors are usually achieved with very small amounts
of copper (i.e. 0.2-0.5%) in a low alumina base with at least .4 molar
equivalents of CaO and plenty of the alkalis. Tin oxide will enhance
color. Use of silicon carbide in oxidation (2%) can produce red.
--
=3DA0Lee Love in Minneapolis
http://mingeisota.blogspot.com/
=3DA0"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D9=
7that is, =3D
"The
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
Lee on mon 31 jan 11
On Mon, Jan 31, 2011 at 12:37 AM, David Finkelnburg
wrote:
> Bob,
> =3DA0 =3DA0Copper reds are almost entirely achieved in the firing. =3DA0M=
ost
> glossy glazes with 0.7 moles CaO and copper as a colorant have enough iro=
=3D
n
I posted this to Bob privately and am surprised that someone else hasn't
posted yet. I know this about copper because of trying to get copper gree=
=3D
ns in
reduction (you go with high alkali, higher alumina for green):
You want low alkali, low alumina for best copper reds.
Oxides - Cu2O
Copper is well-known for its ability to produce blood-red and fire-red
colors in steady reduction atmosphere firings where CuO is altered to
Cu2O. Bright red colors are usually achieved with very small amounts
of copper (i.e. 0.2-0.5%) in a low alumina base with at least .4 molar
equivalents of CaO and plenty of the alkalis. Tin oxide will enhance
color. Use of silicon carbide in oxidation (2%) can produce red.
--
=3DA0Lee Love in Minneapolis
http://mingeisota.blogspot.com/
=3DA0"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D9=
7that is, =3D
"The
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
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