Bob Hanlin on mon 16 sep 96
Folk:
I need a good rutile blue glaze. I fire at cone 10 reduction. I work
primarily in copper red. I uses some other glazes also but want to expand
my glaze colors to include some rutile blues. Can anyone help?
Thanks
Bob Hanlin
3504 N. Tulsa
Oklahoma City, OK 73112
e-mail bhanlin@ionet.net
Bob H in OKC
e-mail bhanlin@ionet.net
Paul on fri 25 oct 02
I am still gathering info about how others fire their rutile blue glazes.
Mine are coming out white most of the time. I plan to slow the firing down
and soak longer, but in the mean time i would very much like to hear some
success stories with this type of glaze:
Dolomite 15.8
Custer Spar 30.0
Whiting 11.1
EPK 16.8
Flint 26.3
Rutile 8.0
I fire to cone 11 in a rather heavy reduction, in about 9 hours. I wonder
why there are volumes of info about copper reds which give me very little
trouble anymore, yet the rutile blue remains a mystery. One person told me
he has been making his living for 30 years off rutile blues but still does
not know exactly what makes it turn blue, aside from the fact that a
specific firing schedule involving a soak seems to help.
Any info would be greatly appreciated. Thanks!
Paul B
June Perry on fri 25 oct 02
You didn't say how early you begin reduction. I used a C10 rutile blue glaze
for years (Moonlight), and I always reduced very early -- 1550F or even
earlier at times. I used both iron bearing stonewares and porcelain. The
heavier the reduction, the darker the blue was the case with Moonlite.
Do you use an oxyprobe? If not, maybe you can borrow one to make sure that
you are getting the reduction you think you're getting.
My firings were usually 12 -15 hrs sometimes even less, and sometimes with
very little soaking, so my guess, based on my own experience would be that it
wouldn't be the lack of soaking that is preventing the blue.
Are you applying the glaze thick enough?
Some glazes begin their melt very early, and maybe you just need earlier
reduction.
Regards,
June Perry
http://www.angelfire.com/art2/shambhalapottery/index.html
Craig Martell on sat 26 oct 02
Hi Rooteel Enthusiasts:
We had a discussion about the nature of these glazes sometime
back. Trouble is, I can't remember if this was on Clayart, or Ian Currie's
glaze list. You might look at the archives for this info.
I think that these glazes develop color by an optical effect rather than by
taking the color into solution. In other words, it's a light refracting
effect that causes the blue. If you can acquire a copy of Ian Currie's
first book, Stoneware Glazes, A Systematic Approach, there is some good
information about "the Chun Blue Effect" which applies to rutile blues. I
actually think that rutile blue glazes are chuns that gain some enhancement
from the rutile. Chuns require a certain amount of undissolved material,
usually silica, of a certain particle size to refract the light and produce
the chun blue. Some phosphorous will enhance this as well. The Chun
effect is also dependent on an iron bearing body or perhaps porcelain with
an iron slip. Ergo, given that rutile carries both iron and titanium, this
material may very well enhance and amplify the effect of a chun. Titanium
is an opacifier which could supply some of the undissovled particles
necessary for light bending and the iron could enhance this effect by doing
what it does.
I would also think that magnesia materials could negate the blue by
crystallizing during cooling thereby inhibiting the passage of light thru
the glaze. Dolomite and talc for example could be eliminated or decreased
if the blue is not appearing. The cooling rate would be a factor too as a
slower cool would allow more crystallization in the glaze.
These are tricky glazes to make and fire but when you get one in the bag,
they are very nice. If I were wanting to make rutile blues, I would
approach this by doing some Currie biaxial grids to find a point where the
light bending is about right. I found a very nice chun base using the
biaxial grid and I don't think I would have thought of this particular
blend and % of materials without doing what I did.
regards, Craig Martell Hopewell, Oregon
Rick Hugel on sat 26 oct 02
Don't know it this will help, but here is my experience with the glaze. It
is a bit of a frustrating glaze. I found out very quickly that using it on
a fine particle clay with very little to no iron in it just doesn't work.
The results will always be white UNLESS the pot has finger grooves or is
altered in a way that allows the glaze to pool in valleys and crevices
where it will turn blue. And even this is chancy. So I just don't use the
glaze on anything but sandy heavy iron bearing clay and these pots are
usually vases which have been altered in some way. The results always show
off the glaze at its best. As for firing, I don't do anything special.
Pots with this glaze are mixed in with everything else and fired in my
usual reduction method: 13 hours, 1280 degrees centigrade oscillating
between reduction, neutral,heavy reduction,neutral beginning from 900
degrees centigrade. Between 700 degrees to 800 I stretch out the firing
time to 3 hours with about half the time spent at the 800 mark. This is
done between neutral and very light reduction, sometimes slipping to
oxidization. I have never used cones. I always go by the color of the
flame in either the peep hole or the flue. I wish you luck because it is a
really beautiful glaze.
Rick
>I am still gathering info about how others fire their rutile blue glazes.
>Mine are coming out white most of the time. I plan to slow the firing down
>and soak longer, but in the mean time i would very much like to hear some
>success stories with this type of glaze:
>
>Dolomite 15.8
>Custer Spar 30.0
>Whiting 11.1
>EPK 16.8
>Flint 26.3
>Rutile 8.0
>
>I fire to cone 11 in a rather heavy reduction, in about 9 hours. I wonder
>why there are volumes of info about copper reds which give me very little
>trouble anymore, yet the rutile blue remains a mystery. One person told me
>he has been making his living for 30 years off rutile blues but still does
>not know exactly what makes it turn blue, aside from the fact that a
>specific firing schedule involving a soak seems to help.
>Any info would be greatly appreciated. Thanks!
>Paul B
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
>melpots@pclink.com.
iandol on sun 27 oct 02
Dear Paul,
You suggest <<...yet the rutile blue remains a mystery.>>
It is possible that this phenomenon has already been explained by K. =
Koumanin through proposing the formation of a lower oxide or possibly a =
Titanium ion with three positive charges (Ti^3+). See "Ceramic Research =
Institute, Moscow. Paper No 8, 1927.
There is a suggestion in the literature also that the blue colouration =
is ephemeral. To achieve a persistent blue colour it seems that it is =
necessary to cool under reducing conditions otherwise the hue reverts to =
a grey violet. My suggestion would be to maintain a reducing atmosphere =
until ware cools below the glass transition temperature.
Experience tells me that the Violet colour is physical rather than =
chemical in nature. Someone recently mentioned Greg Daly and his Base =
Glaze F (p 14. Glazes and Glazing Techniques.) With 15% Titanium =
Dioxide, fired to Cone 10 this gave a violet effect which was almost =
invisible close up but intense when viewed from a distance.
Perhaps the answers to questions about the colours imparted by Titanium =
Dioxide, the minerals Rutile and Ilmenite will be found in a deeper =
understanding of the relationships between Ti and O2. Nor should we =
ignore the potential influence of trace elements in the natural =
minerals.
Best regards,
Ivor Lewis.
June Perry on sun 27 oct 02
Ivor, my experience with a fast cooling, Geil fiber kiln has shown that you
don't need a reduction cooling to get good rutile blues.
I think you need to avoid a too thin application of the glaze, start
reduction early and maintain reduction throughout. Iron bearing stoneware can
also aid in the color; but as one poster mentioned, they have seen great
rutile blues on white bodies, as have I.
My standard rutile glaze, Moonlight that many US potters use, in reduction
ranges from a pale lilacy blue to a deep purplish blue on the same body,
depending on the amount of reduction -- all naturally fast cooled in the
fiber kiln with no firing down.
I also think that some low temp melting fluxes like Zinc oxide, which is in
the Moonlight base (1.9%), and boron, which is also in the Moonlight glaze
(14.3 Colemanite), can help the early melt and along with the early
reduction can aid in giving good rutile blues. The moonlight also has a low
clay content (4.8 EPK), with the rest of the alumina satisfied in the
Cornwall stone (63.8%), with 7.6 whiting and 7.6 silica completing the base
recipe.
I think the work that Craig has done using the Ian Currie method is a great
idea.
I have been fascinated and frustrated with chuns for years! LOL They are
beautiful glazes that seem to look their best right before they head south to
the kiln shelf! :-)
Regards,
June Perry
http://www.angelfire.com/art2/shambhalapottery/index.html
Lesley Alexander on tue 29 oct 02
With all this talk of reduction, I'm wondering why I got a muddy grey
with my rutile glaze when I fired it wih a shino firing. Was it the
particular version of rutile blue, or is there a general caution about
not firing it too reduced? Lesley
June Perry on wed 30 oct 02
Lesley, it could be the formula, or the formula on your claybody. Some rutile
blues look great on white bodies and darker, greyish on others. Some are
great on iron bearing bodies, but washed out on a white body.
It could be that the thickness of the glaze is the culprit. If too thin, you
can get that grey, flat look.
It's probably best to find a recipe that is more tolerant of the many
variables of application, choice of clay body and firing technique.
Regards,
June Perry
http://www.angelfire.com/art2/shambhalapottery/index.html
Lisa-Marie Serafin on wed 30 oct 02
Lesley,
I found that if I placed a piece with a blue rutile glaze higher up in the
kiln it became (ugh) beige! The best location in a reduction firing for me
was to put the rutile pieces at the bottom or very near to the bottom where
reduction was lighter. We fired in a 14 cu ft Geil gas kiln to cone 9.
Lisa-Marie Serafin
Maker of Fine Functional Pottery
Lac la Blanche, PQ
----- Original Message -----
From: "Lesley Alexander"
To:
Sent: Tuesday, October 29, 2002 4:18 PM
Subject: Rutile Blue Glazes
> With all this talk of reduction, I'm wondering why I got a muddy grey
> with my rutile glaze when I fired it wih a shino firing. Was it the
> particular version of rutile blue, or is there a general caution about
> not firing it too reduced? Lesley
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
>
| |
|
