Malone & Dean McRaine on sat 18 oct 97
Aloha all;
Hawaii is particularly hard on copper matt type glazes, they oxidize quickly
here. Even stainless steel rusts. If they're going to oxidize they do it
pretty quickly here so it's a good proving ground. I haven't found any
coating that I liked or that was very permanent. I think that if your glazes
are oxidizing it's because they haven't been melted well enough. I suggest
you try two things, apply your glaze thicker, and soak the glaze, much as
you would a high fire glaze to make sure you get a good melt. Just getting
a good visual of a melted glaze for 5 minutes may not be enough. I have raw
glazed raku pots, bisqued them to ^06 with a 1/2 hr soak, and then done a
regular raku firing/reduction and gotten much more durable results. The
glaze goes into the raku fire pre-melted. Another way is to fire a lot
hotter, like to ^1 or 2. This will also get a more complete melt especially
in copper matts. You might also try adding a little silica to your glaze to
fuse it a little more.
Let me know if this helps I'm still working on this problem myself.
Dean from hot & sunny Kauai.
Geoffrey Barst on sun 28 aug 05
Some tips on achieving the brilliant colors available with copper matt in
raku would be appreciated. The unglazed portion of the pot I want to be
black so will have to reduce it for a time to achieve that. I have been
getting copper colored effects but not the brilliant blues & reds I
desire. Is it necessary to re-oxidise while the pot is still hot? How much
reduction is necessary? Does one freeze the effect still by plunging into
water? How does the thickness of application affect the final color? Can
re-heating areas with a blowtorch or re-firing the pot rehabilitate a
mediocre finish?
I know there is a lot of trial & error involved but someone out there has
got it right more often than not. Help would be appreciated.
Geoff Barst
Robert W. Anderson on sun 28 aug 05
Geoff,
Try applying your copper matt very thin (like water).
Fire to 1900 F. Put two brown paper bags
together...a couple lightly balled up newspaper
pages in the bottom of the double bag. Place in
your reduction barrel...your hot raku piece goes in the
sack...let the fire lick your pot for 3-5 seconds before
covering the chamber. Reduce 15-20 min...plunge in
water. Try it again. Good luck.
Bob
----- Original Message -----
From: "Geoffrey Barst"
To:
Sent: Sunday, August 28, 2005 10:14 AM
Subject: Copper matt raku
> Some tips on achieving the brilliant colors available with copper matt in
> raku would be appreciated. The unglazed portion of the pot I want to be
> black so will have to reduce it for a time to achieve that. I have been
> getting copper colored effects but not the brilliant blues & reds I
> desire. Is it necessary to re-oxidise while the pot is still hot? How much
> reduction is necessary? Does one freeze the effect still by plunging into
> water? How does the thickness of application affect the final color? Can
> re-heating areas with a blowtorch or re-firing the pot rehabilitate a
> mediocre finish?
>
> I know there is a lot of trial & error involved but someone out there has
> got it right more often than not. Help would be appreciated.
>
> Geoff Barst
>
>
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Millard Balfrery on sun 28 aug 05
Geoffery,
I've been expermentin' with various raku clay bodies and glazes. Mix the
white #14 miami clay w/ #15 black to make a red/pink body. So far I've only made
three successfull firings. I rebuilt an old professionally designed homemade LP
gas fired catanery arched downdraft front loading 10 cu ft kiln. It is
massive compared to the size of the firing chamber. It takes about 3 hours to get to
06. I fired some pieces in my friend's 15 cu ft natural gas updraft kiln with
good results.
At the local high school I took the nighttime ceramic class to polish my
throwing skills and to use thier raku kiln- a simple updraft cylinder of expanded
metal lined with a lightweight ceramic fiber blanket. The teacher is young,
but exceptionally talanted and a good communicator. The glazed bisque ware was
fired to 1850 F using a cheapo digital pyrometer. At night the ware goes thru a
series of color changes. red, red-orange, orange, orange-yellow, and
yellow-white at 1850F. Using the MSMD method I guage the temperature at yellow-white
as I lack a pyrometer, Monkey See Monkey Do!
It appears to me using a copper based glaze from Axner Supply, "Gatorskin",
that the most important factors are to fully reach 06, to seal the reducing
chamber tightly with wet newspaper, have newspapers wrapped and wet, ready to go
so you're not fumbling when the pots are ready. I used newspaper on some
reductions, others I used sawdust, leaves, wet corn shuckin's, and sargasum
seaweed. Got almost the same results on all except more violet with the seaweed. On a
couple pots I glazed with Mayco Crackle white and beige- drop dead gorgeous!
On others I put down two layers of a turquoise on a flat area and gatorskined
over- a very nice effect
Keep good notes, you think you can remember what sequence, thickness,
combonation of glazes you used- but you Will forget.
As far as using a torch to 'rehabiltate' a less than satisfactory glaze, save
your time and effort and put them aside to reglaze/refire at a later date as
a torch will not reach high enuf temperatures. The high school teacher opened
the reduction bucket on some pieces to turn a piece while still in flux and
'even' it out, then would pick it up and quench it in a bucket of water. I find
that this water process is chipping a fair amount of pots, from the points on
the tongs! More pots to be reglazed.
I've been kicking around the idea of adding a oil drip to stretch the LP gas-
don't know if it's worth the trouble, might create more problems!
We dodged Katrina last Thursday as the weather guesser predicted she would
hit about 20 miles south on the Palm Beach/ Broward County line- hit 60 miles
south in Dade County instead. Looks as the people in the area around New Orleans
won't be so lucky. Say a prayer for them.
Ignorance can be a powerfull tool, if applied at the right time it usually
surpasses Knowledge.
Best Regards, Millard 'Mill' Balfrey
millcharlie@wmconnect.com
Leland Hall on sun 28 aug 05
What I am about to say, I think you will not find too helpful, yet I feel
compelled to share it with you.
Rober Pipenburg's perenial book "Raku" is to many the first word on the
subject of raku.
In this book he refers to the copper matt glazes as "beguiling". After
fooling around with them for years, I know why he said that.
I think you might have your best luck in your endeavor for the
elusive "brilliant" colors with plenty of open flames before reduction, and
then a short reduction. Some potters deliberately over reduce to straight
copper, them pull the ware, and watch untill the color they like apears,
then quench. I've even met folks with a formulae, so many minutes or
seconds of reduction (with their given reduction material), per ounce of
ware. I'm serious. Of course each reduction material gives different
results. As does the volume of material, as does ambient temp.
Look, there is no one way to achieve the result you ask about. When I
started my raku journey years ago, I asked questions like the ones you have
asked. Really, to little avail.
Your right, your going to have to experiment. And may I recomend as many
workshops as you can swing? Mr. Pipenburg is still doing the workshope
ciruit, and I can tell you it's an experience to be remembered. I'd
recomend his workshops, in fact strongly encourage it if your serious about
raku. He's a legend, and will retire eventually. (Damn!)
Best of luck, and enjoy the journey.
Leland Hall
Before The Wheel Enterprises
Raku Pottery and Sculpture
La Pine, Oregon,
Where I got bored with Copper Matt glazes many years ago, and really only
use them infrequently as accent these days.
On Sun, 28 Aug 2005 11:14:06 -0400, Geoffrey Barst
wrote:
>Some tips on achieving the brilliant colors available with copper matt in
>raku would be appreciated. The unglazed portion of the pot I want to be
>black so will have to reduce it for a time to achieve that. I have been
>getting copper colored effects but not the brilliant blues & reds I
>desire. Is it necessary to re-oxidise while the pot is still hot? How much
>reduction is necessary? Does one freeze the effect still by plunging into
>water? How does the thickness of application affect the final color? Can
>re-heating areas with a blowtorch or re-firing the pot rehabilitate a
>mediocre finish?
>
>I know there is a lot of trial & error involved but someone out there has
>got it right more often than not. Help would be appreciated.
>
>Geoff Barst
>
>___________________________________________________________________________
___
>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.
Marcia Selsor on mon 29 aug 05
I use copper matts all the time for the past 20 years. I find
Piepenburg to be correct that they are elusive as Leland (I think)
mentioned.
I get my best colors when firing in the winter at -20 degrees. But
that is really not fun. I fire my large slabs of 24" in light weight
fiber kilns (3)
about 45 minutes. Much faster and they crack. The kilns can go
faster. I found that the points on the tongs were cracking my slabs ,
so I went to a flat set for the slabs.
I lay them face down in straw and cover with a metal feed bucket. I
have 4. I like the pattern the straw gives the glaze surface.
I spray the dry alligator glaze and a copper sand recipe onto the
slab. For a black surface, I use a latex resist and peel it off after
spraying. If the coat of glaze is too thin, it isn't interesting. I
fire to 1850 F. I never use water on the slabs because they are too
big and they'd crack from uneven temps.
Not long ago someone said there can't be any moisture in the
reduction chamber. Today someone said they seal the chamber with wet
newspaper. I know Steve Brafman uses wet newspaper to seal the
reduction chamber. I don't. I guess it all depends.
Marcia Selsor in Montana
Leland Hall on mon 29 aug 05
Marcia nailed when she said "it all depends".
And the list of what it "all" depends on is almost infinate. Not quite,
but almost.
Facial expression may even be a factor. (just kidding) (maybe)
Seriously, from relative humidity to clay body, to how the planets are
lined up at the time. In my estimation, this is what makes raku so
thrilling.
Leland Hall
Before The Wheel Enterprises
Raku Pottery and Sculpture
Lapine, Oregon
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