David Hendley on wed 11 nov 09
Here's my take: whatever it takes to fire a good copper red
will also produce good rutile blues.
I use the same base glaze for both. When the red comes out
anemic, the blue is likewise washed out. When the red is a
deep beautiful red, the rutile blues are deep and rich as well.
So - early reduction and slow cooling in the 1500-2000 degree
range is what works for me.
The amount of rutile is critical. Run a line blend over several
firings to determine the optimum amount for your situation.
Too much rutile will produce a 'white, almost semi-matt glaze'.
David Hendley
david@farmpots.com
http://www.farmpots.com
----- Original Message -----
>i have tried several very common rutile blue glazes over the years in my 7=
0
> cubic foot kiln. I use one of them all the time but it is combined with
> two
> other glazes and looks pretty nice that way. By itself it is basically a
> white, almost semi-matt glaze.
> The same glaze, with the same firing schedule in a smaller kiln (about
> 40-50 cu ft) where i used to work came out a very nice, glossy and
> variegated blue.
> One time i even accelerated the cooling by leaving the burner ports open
> and keeping the blowers on for a while and the glaze came out just like i=
n
> the smaller kiln. But that kind of cooling cycle didn't work well for my
> other glazes so i will never use it again.
steve graber on thu 12 nov 09
i use two rutile commercial glazes from aardvark (or laguna clay).=3DA0 the=
y =3D
each come out STUNNING when added over a Tenmoku glaze.=3DA0 i swear it's t=
ha=3D
t base of iron that really makes the glazes stunning!=3D0A=3D0Ai have used =
in a=3D
refurbished hard brick kiln with cloth insulation cover.=3DA0 it cooled so=
f=3D
ast i could do two cone 10 fires in a day.=3DA0 NICE blues or=3DA0reds.=3DA=
0 (jen=3D
sen blue, jensen red glazes)=3D0A=3DA0Steve Graber, Graber's Pottery, Inc=
=3D0ACla=3D
remont, California USA=3D0AThe Steve Tool - for awesome texture on pots! =
=3D0Aw=3D
ww.graberspottery.com steve@graberspottery.com =3D0A=3D0A=3D0AOn Laguna Cla=
y's we=3D
bsite=3D0Ahttp://www.lagunaclay.com/blogs/ =3D0A=3D0A=3D0A=3D0A----- Origin=
al Message=3D
----=3D0A> From: Paul Borian =3D0A> To: Clayart@LS=
V.CE=3D
RAMICS.ORG=3D0A> Sent: Wed, November 11, 2009 7:45:07 PM=3D0A> Subject: Rut=
ile =3D
blue in slow cooling kilns?=3D0A> =3D0A> i have tried several very common r=
util=3D
e blue glazes over the years in my 70=3D0A> cubic foot kiln. I use one of t=
he=3D
m all the time but it is combined with two=3D0A> other glazes and looks pre=
tt=3D
y nice that way. By itself it is basically a=3D0A> white, almost semi-matt =
gl=3D
aze.=3D0A> The same glaze, with the same firing schedule in a smaller kiln =
(a=3D
bout=3D0A> 40-50 cu ft) where i used to work came out a very nice, glossy a=
nd=3D
=3D0A> variegated blue.=3D0A> One time i even accelerated the cooling by le=
avin=3D
g the burner ports open=3D0A> and keeping the blowers on for a while and th=
e =3D
glaze came out just like in=3D0A> the smaller kiln. But that kind of coolin=
g =3D
cycle didn't work well for my=3D0A> other glazes so i will never use it aga=
in=3D
.=3D0A> =3D0A> i have varied the glaze formula a little over the years but =
stil=3D
l it does=3D0A> not come out blue by itself.=3D0A> just wondering if anyone=
els=3D
e out there with a similar size kiln can get a=3D0A> classic rutile blue to=
c=3D
ome out? and if so, how? I am not referring to=3D0A> the "woo blue" type th=
at=3D
has iron and rutile (they don't come out very nice=3D0A> either though) bu=
t =3D
just the ones that rely totally on rutile.=3D0A> =3D0A> BTW one time i fire=
d th=3D
e exact same glaze i use in an old electric kiln=3D0A> coverted to gas, fir=
ed=3D
and cooled very fast to about cone 12 and the glaze=3D0A> came out the bes=
t =3D
i have ever seen it - very glossy with all kinds of=3D0A> light/dark blue t=
in=3D
ts. So i know that a faster cooling works for it. What i=3D0A> have never f=
ig=3D
ured out is, can the glaze be adjusted so that it does not=3D0A> need a fas=
t =3D
cooling?=3D0A> =3D0A> here is the formula:=3D0A> dolomite 15.8=3D0A> g200 3=
0=3D0A> wh=3D
iting 11.1=3D0A> epk 16.8=3D0A> silica 26.3=3D0A> rutile 8=3D0A> =3D0A> tha=
nks,=3D0A> P=3D
aul=3D0A=3D0A=3D0A=3D0A
Paul Borian on thu 12 nov 09
i have tried several very common rutile blue glazes over the years in my 70
cubic foot kiln. I use one of them all the time but it is combined with two
other glazes and looks pretty nice that way. By itself it is basically a
white, almost semi-matt glaze.
The same glaze, with the same firing schedule in a smaller kiln (about
40-50 cu ft) where i used to work came out a very nice, glossy and
variegated blue.
One time i even accelerated the cooling by leaving the burner ports open
and keeping the blowers on for a while and the glaze came out just like in
the smaller kiln. But that kind of cooling cycle didn't work well for my
other glazes so i will never use it again.
i have varied the glaze formula a little over the years but still it does
not come out blue by itself.
just wondering if anyone else out there with a similar size kiln can get a
classic rutile blue to come out? and if so, how? I am not referring to
the "woo blue" type that has iron and rutile (they don't come out very nice
either though) but just the ones that rely totally on rutile.
BTW one time i fired the exact same glaze i use in an old electric kiln
coverted to gas, fired and cooled very fast to about cone 12 and the glaze
came out the best i have ever seen it - very glossy with all kinds of
light/dark blue tints. So i know that a faster cooling works for it. What i
have never figured out is, can the glaze be adjusted so that it does not
need a fast cooling?
here is the formula:
dolomite 15.8
g200 30
whiting 11.1
epk 16.8
silica 26.3
rutile 8
thanks,
Paul
Bruce Girrell on thu 12 nov 09
Steve Graber wrote:
i use two rutile commercial glazes. they each come out STUNNING when added=
=3D
over a Tenmoku glaze. i swear it's that base of iron that really makes th=
=3D
e glazes stunning!
Steve -
After a series of experiments involving 13 different rutile blue formulatio=
=3D
ns and all possible combinations of glaze A over glaze B within that group,=
=3D
I came to the same conclusion. What seemed to work best for us was a non-i=
=3D
ron rutile blue (for example, Pete Pinnell's Cash Blue) over an iron-bearin=
=3D
g rutile blue (Woo Blue, for example). But another iron glaze as a base doe=
=3D
s well also. We have often used a rutile blue over a black teadust glaze an=
=3D
d it does well.
Part of it may simply be the darker background. Just as lower quality opals=
=3D
can be improved dramatically by adding a black backing (a "doublet"), it s=
=3D
eems that the opalescence of rutile blues is aided by a darker backing.
Bruce Girrell=3D
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