victoria henriksen on fri 13 feb 04
hello all,
i have been doing raku for the past year or so and have been getting great results (thanks to so much helpful info that i found in the archives). Lately i have started making carved lanterns. I glaze the exterior with a matte, non flashing glaze, or i do the naked raku technique. The interior is glazed with a flashy glaze, so that when a candle is placed inside it illuminates all those marvelous metallic colours....the problem is that i am getting none of those flashy colours at all. I cant seem to be able to get any of the glazes to flash on the inside. I have tried 3 different glazes ( Tom Buck's revised copper sand, Bwiners silver, and a laguna commercial glaze called tutti Fruitti). I thought that maybe this was due to the fact that the lanterns would be cooler inside than out so i tried firing them hotter (i dont fire with a pyrometre, i just look at glaze and kiln colour), and then hotter with a 10 minute soak. But this didnt change anything.
Maybe the problem occurs in the reduction bins? does the glaze actually need contact with reduction material in order to flash? i usually use newspaper and glossy magazines with great results, but it would be difficult to get that inside the lantern.
If anyone has any suggestions i would be a happy girl...
thanks in advance
Victoria
---------------------------------
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daniel on sat 14 feb 04
Hi Victoria,
If you've only tried them on the inside and not often - you sound like you
have only recently tried some of these - have you been able to get better
effects with them on the outside of a piece ? It would be worth making sure
that you can sucessfully fire them this way, I think.
Given that's all ok then here are my guesses.
I rarely if ever glaze the inside of pieces but at one place I do raku a
lot of people try various things including this. I have noticed that the
glaze tends to be duller in such cases, I'm thinking of mattes here. I can't
recall much concerning lusters in this respect. I suspect that there is some
sort of problem with either getting enough reduction or slow cooling (due to
retention of heat in the enclosed form) allowing some oxidation to occur as
air leaks into the bins. Please note that this is a sort of vague feeling. I
have not really tried experiments here. Perhaps I should.
It is certainly not necessary to have the combustible touch the object to
get colour reactions. I personally try to avoid that on soft glazes like
lusters as I don't like the surface that can result.
So having offered a rather useless 2c, one question is, what does the glaze
look like on the inside ? Does it look oxidized or weakly reduced ? How does
it compare with an outside-glazed example ?
Thanx
D
Craig Dunn Clark on sat 14 feb 04
Victoria, unless you are firing your refractory slip- aka "naked raku"-
much higher than anyone that I have seen or read about then the glazes that
you have on the inside of the pieces will not likely mature. They will end
up rather dull after each firing.
If you fire the refractory slip up to the maturation point of many
different raku glazes you will most likely have a great deal of difficulty
removing the slip. Most folks who I have listened to say that they remove
the "naked raku" pieces around a dull red heat. This is what has worked for
me. I believe that this is where you may be having difficulties.
The glazes, when mature, do not need to be in direct contact with the
reduction material. Some folks go as far as to encase their pieces in
stainless steel mesh containers so that there is not any possiblity of this
happening. It is dependant upon what you are after.
In the post firing reduction phase it is the carbon in the atmoshpere of
the chamber reacting with the metallic oxides in your glazes that give you
all of the pretty colors. It has to do with carbons affinity for oxygen.
The different materials that you use for reduction have varying results
do to inherent differences in the materials that affect the rate at which
they combust. If you use thicker paper or coarser material they will not
burn as readily and will often leave a physical imprint in the glaze if
contact occurs. Atleast that is the case with the thicker glossy type glazes
to which you refer. In the case of the "alligators" or copper matts it is a
different ballgame. Not much of a glaze there inwhich to leave an
impression.
Try firing a smaller piece as you normally would. USe the manner with
which you have been successful. Along side it place a lattern type test
piece. Fire them both up together. Look for that nice bright orange glow in
the kiln and a reflection off the surface of the glossy glaze that you know
how to fire. WHen you open the kiln pull the glossy piece quickly and put it
into reduciton. Then follow it up into another can with the test latern.
Compare the pieces after the fact side by side. Chances are you will
have a gloss on the inside of the test lattern but have a really hard time
getting the slip off the outside.
Hope this helps
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
----- Original Message -----
From: "victoria henriksen"
To:
Sent: Friday, February 13, 2004 10:17 AM
Subject: raku question for you afficionado's
> hello all,
> i have been doing raku for the past year or so and have been getting great
results (thanks to so much helpful info that i found in the archives).
Lately i have started making carved lanterns. I glaze the exterior with a
matte, non flashing glaze, or i do the naked raku technique. The interior is
glazed with a flashy glaze, so that when a candle is placed inside it
illuminates all those marvelous metallic colours....the problem is that i am
getting none of those flashy colours at all. I cant seem to be able to get
any of the glazes to flash on the inside. I have tried 3 different glazes
( Tom Buck's revised copper sand, Bwiners silver, and a laguna commercial
glaze called tutti Fruitti). I thought that maybe this was due to the fact
that the lanterns would be cooler inside than out so i tried firing them
hotter (i dont fire with a pyrometre, i just look at glaze and kiln colour),
and then hotter with a 10 minute soak. But this didnt change anything.
> Maybe the problem occurs in the reduction bins? does the glaze actually
need contact with reduction material in order to flash? i usually use
newspaper and glossy magazines with great results, but it would be difficult
to get that inside the lantern.
> If anyone has any suggestions i would be a happy girl...
> thanks in advance
> Victoria
>
>
>
> ---------------------------------
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Wally on mon 16 feb 04
Craig,
I agree. Firing temperature of "naked raku" is quite critical, and
the most common cause of bad results....
As soon as the raku glaze starts "bubbling", or as I say appears
like the "orange-peel-look", temperature increase should be
stopped. Just candle for 5 or 10 minutes and withdraw to a
reduction environment.
Even when overfired, the "refractory slip" can still be removed...
Soaking 24 or 48 hours in water may help.
If not, a 12-hour retreat in your freezer is the ultimate solution.
Wally.
-- In clayart@yahoogroups.com, Craig Dunn Clark wrote:
> Victoria, unless you are firing your refractory slip-
aka "naked raku"-
> much higher than anyone that I have seen or read about then the
glazes that
> you have on the inside of the pieces will not likely mature. They
will end
> up rather dull after each firing.
> If you fire the refractory slip up to the maturation point of
many
> different raku glazes you will most likely have a great deal of
difficulty
> removing the slip. Most folks who I have listened to say that they
remove
> the "naked raku" pieces around a dull red heat. This is what has
worked for
> me. I believe that this is where you may be having difficulties.
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