Chess Denman on wed 18 aug 99
I have been trying to get in to raku recently. I have built my raku kiln and
am making my first batch of stuff for firing. However I am very confused
about reduction.
I have been reading Ian Byers book to try to get a handle on things and some
glaze recipies. He talks about colour responses of some glazes in oxidation
and reduction eg "Reduction rather than oxidaton will also affect the colour
of many glazes........." but he also talks about post firing reduction with
hay or sawdust etc. But when he talks about copper matt surfaces it isn't
clear if he means the surfaces to be reduced while firing as well as being
flamed afterwards.
Do people reduce while firing raku glazes (by closing the flue I guess) or
only afterwards.
chess
Marvin Flowerman on thu 19 aug 99
Chess:
Yes, generally during the last few (5-10) minutes of firing I close the flue,
see a 5 inch or so tongue of flame coming out of the peep hole, and then
close down the gas feed, open the kiln and remove the pieces to the post
reduction buckets in which I have placed a good quantity(two or three hand
fulls) of dried leaves and hardwood shavings.
I have seen some references to a reduction period before the glaze melts but
have not tried that procedure yet; sounds like a type of body reduction.
Good luck!
Marvin Flowerman (marvpots@aol.com)
Bruce Girrell on thu 19 aug 99
> Do people reduce while firing raku glazes (by closing the flue I guess) or
> only afterwards.
Chess,
I can't answer regarding the copper matte, but as far as the above question
goes, I can say very definitely that oxygen control during the firing is
important.
For reference, see a vase that Lynne and I made on one of Faye Cassman's
Clayart pages:
http://clay.justnet.com/gallery/bgirrell.htm
The glaze on this vase is Tom Buck's Red Lustre #8 and the red color was
developed during firing by keeping the kiln in reduction. The very same
glaze, same clay body, same thickness, same underglaze produces a khaki
green when fired in oxidation. When the pot come out of the kiln, the basic
color is set. Post fire reduction then alters the basic color, adding
flashes of copper, reds, blues, yellows, and iridescence.
Some glazes, such as white and cobalt blue, just don't care too much whether
the kiln is in oxidation or reduction during firing. Copper is the rainbow
magician. It can do just about anything depending on when and how much
oxygen you give it or take away. The big trick is trying to control it.
Lynne says that raku is kind of like opening Christmas presents - you can
hope, but you never know what you're going to get. Sometimes you get socks
and underwear; sometimes you get the toy you've been wanting all year.
Good luck. May Santa bring you many toys.
Bruce and Lynne Girrell
in Northern Michigan, where we say our first orange tree branch yesterday.
NOOOOooooo.... Fall can't be coming yet!
Kim Peterson on thu 19 aug 99
>From: Chess Denman
>Reply-To: Ceramic Arts Discussion List
>To: CLAYART@LSV.UKY.EDU
>Subject: very basic raku question
>Date: Wed, 18 Aug 1999 12:49:12 EDT
>
>----------------------------Original message----------------------------
>I have been trying to get in to raku recently. I have built my raku kiln
>and
>am making my first batch of stuff for firing. However I am very confused
>about reduction.
>
>I have been reading Ian Byers book to try to get a handle on things and
>some
>glaze recipies. He talks about colour responses of some glazes in oxidation
>and reduction eg "Reduction rather than oxidaton will also affect the
>colour
>of many glazes........." but he also talks about post firing reduction with
>hay or sawdust etc. But when he talks about copper matt surfaces it isn't
>clear if he means the surfaces to be reduced while firing as well as being
>flamed afterwards.
>
>Do people reduce while firing raku glazes (by closing the flue I guess) or
>only afterwards.
>
>chess
Chess,
The basic premise of Raku is to fire the "pot" until the glazes liquify,
remove them from the kiln, dump them into a "pit", and cjover the pit until
relatively cool.
Temp is about cone 012-08 at the end of the firing. Open the kiln. Remove
the piece with tongs... If you are going to reduce, the pit or barrel or
what ever closable container which won't burn (I've seen a reduction in a
paper box). If you want a heavy reduction cover it with sawdust or something
which gives a lot of smoke (therefore no oxygen). You can let it reduce
until cold.. or cool and dip into water. Wash with a scrubby.. even as
abrasive as a brillo pad (SOS pad). Enjoy.
Oxydation. Let the piece cool in the air. This may be effective with crackle
glazes.
Coppers... If you want a red.. Heavy reduction Don't let it tarnish!
If you want greens. oxydize.
Play with the stuff have fun. Don't be suprised if you get some cracks
Biggest thing. Have fun. Relax. Burn some clay.
Kim A Peterson
kimpeterson10@hotmail.com
_______________________________________________________________
Get Free Email and Do More On The Web. Visit http://www.msn.com
=?iso-8859-1?Q?Fran=E7oise?= Melville on thu 19 aug 99
Yes, Chess. When I want to achieve copper reds in raku firings, I
partially close the flue and reduce when I see the glaze is melting. More
often than not, I still put the pot in the reduction can.
Francoise
Indalo Pottery
http://members.tripod.com/~indalopottery
Harvey Sadow on thu 19 aug 99
Chess,
I have often fired copper matte surfaces in as little as 3 minutes. No
time for reduction in the kiln at that speed. Generally, I do not fire
them for more than 10-15 muinutes and I never reduce them inside the
kiln. Anyone who has taken a raku workshop with me can attest to this
fact. I will fire about as fast as the kiln can go and I put the pieces
in at 800-1200 deg. F. Much more important is how the piece is removed,
reduced and cooled after the firing. Application is also important. I
was just demonstrating that in a class raku firing last night.
Harvey Sadow
Mike Gordon on fri 20 aug 99
Hi Harvey,
That speed is pretty amazing! What kind of clay do you use? I raku fer
around 30-45 min . - fear of blowing things up. Mike
| |
|
