KYancey on mon 27 mar 00
Hi all, I was wondering if anyone would be willing to share some
techniques on how to achieve those beautiful vibrant red copper matt or
those luminous blue matt surfaces on raku pottery. So far I've been
using Mark's Copper Matt from the Branfman Book. Frit 3110 10%, Copper
carb 90%, Iron Oxide 5%. I fire in a fiber lined oil drum in oxidation
to cone 11. Place it in post reduction for about 15 to 30 minutes. So
far I've achieved a muddy, dark purple, some bright greens (nice) and
very pretty flashing. However, I would like to see if I can produce an
attractive, more uniform, red or blue. Any advise will be much
appreciated. Thank you Ken
Cantello Studios on tue 28 mar 00
+++++++++++++++++++++++++
+++ Raku Gold ^06 +++
+++++++++++++++++++++++++
Firing type: Raku
Glaze type: Raku (Copper matt)
Color: copper flash
Surface: Matt
Transparency: Opaque
Crystals: None
Bubbles: None
Flow: None
Flaws: Crawls\when thick
Durability: Good
Testing: good one
Date: 02/16/00
Gerstley borate 62.64 62.6%
Nepheline syenite 13.19 13.2%
Bone ash 20.88 20.9% Hazard!
Frit 3124 3.3 3.3%
-------- ------
100 100 %
Copper carbonate 6.59 6.6% Hazard!
Cobalt carbonate 1.65 1.6% Hazard!
Manganese dioxide 2.2 2.2% Hazard!
Notes:
You must flash the pot quickly with in 10 to 15 sec. after its been
in the can. Then leave be, to cool slow for 25 min.
Material Hazards:
Bone ash - skin irritant
Copper carbonate - poisonous - fumes can be toxic above c/8
Cobalt carbonate - irritant
Manganese dioxide - poisonous
Cost: $ 2.92 per kg glaze
$ 0.29 per 100 g batch
===========================
Chemical Analysis
===========================
This glaze contains unexpected oxides: SiO2
Na2O 0.04 Al2O3 0.05 P2O5 0.10
K2O 0.01 B2O3 0.72
CaO 0.81
MnO 0.04
CoO 0.02
CuO 0.08
Alumina:Silica ratio is 1.00 : 4.68
Neutral:Acid ratio is 1.00 : 0.12
Alkali:Neutral:Acid ratio is 1.00 : 0.78 : 0.10
Na2O 1.6% Al2O3 3.8% P2O5 9.5%
K2O 0.8% B2O3 34.8%
CaO 31.2%
MnO 1.9%
CoO 1.1%
CuO 4.6%
This glaze also contains:
SiO2 10.6%
Loss On Ignition: 16.1%
Expansion coefficient: 84.8 x 10e-7 per degree C
Oxides causing abnormal expansion effects: B2O3
Surface Tension index: 2.5
Materials in glaze:
Gerstley borate provides B2O3 and CaO.
Nepheline syenite provides SiO2, Al2O3, Na2O, and K2O
Bone ash provides CaO and P2O5. Usually used as an opacifier.
Frit 3124 supplies SiO2, Al2O3, CaO, B2O3, Na2O, and a trace of K2O..
Copper carbonate provides CuO. Used as a colorant.
Cobalt carbonate provides CoO. Used as a colorant, acts as flux.
Manganese dioxide provides MnO. Used as colorant.
Oxides in glaze:
Na2O is a strong alkaline flux.
K2O is a strong alkaline flux.
CaO is a high-temperature flux.
MnO is a colorant (black, brown, and purple).
CoO is a colorant (blues and purples).
CuO is a colorant (greens, blue-greens, reds, and copper lusters).
Al2O3 increases viscosity, prevents crystallization, and adds durability.
B2O3 is both a glass-former and a flux over a wide temperature range.
P2O5 is a glass-forming oxide and opacifier.
SiO2 is the primary glass-former in glazes.
=======================
Cost Summary
=======================
Gerstley borate 62.6% $ 0.65 per kg glaze
Nepheline syenite 13.2% $ 0.06
Bone ash 20.9% $ 0.60
Frit 3124 3.3% $ 0.10
------ -------
100 % $ 1.40 per kg glaze
Copper carbonate 6.6% $ 0.65 per kg glaze
Cobalt carbonate 1.6% $ 0.80
Manganese dioxide 2.2% $ 0.06
-------
$ 1.51 per kg glaze
Total cost: $ 2.92 per kg glaze
$ 0.29 per 100 g batch (You Can E-Mail Me At
Tleecan@2xtreme.net) Chris
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.UKY.EDU]On Behalf
Of KYancey
Sent: Monday, March 27, 2000 12:04 PM
To: CLAYART@LSV.UKY.EDU
Subject: RAKU: Copper Matt Techniques
----------------------------Original message----------------------------
Hi all, I was wondering if anyone would be willing to share some
techniques on how to achieve those beautiful vibrant red copper matt or
those luminous blue matt surfaces on raku pottery. So far I've been
using Mark's Copper Matt from the Branfman Book. Frit 3110 10%, Copper
carb 90%, Iron Oxide 5%. I fire in a fiber lined oil drum in oxidation
to cone 11. Place it in post reduction for about 15 to 30 minutes. So
far I've achieved a muddy, dark purple, some bright greens (nice) and
very pretty flashing. However, I would like to see if I can produce an
attractive, more uniform, red or blue. Any advise will be much
appreciated. Thank you Ken
Susan Goldstein on tue 28 mar 00
In a message dated 03/27/2000 3:06:51 PM Eastern Standard Time,
kyancey1@tampabay.rr.com writes:
<< raku pottery. So far I've been
using Mark's Copper Matt from the Branfman Book. Frit 3110 10%, Copper
carb 90%, Iron Oxide 5%. I fire in a fiber lined oil drum in oxidation
to cone 11. >>
I never heard of firing raku to cone 11. Is this a mistake?
Susan
KYancey on wed 29 mar 00
Yes, thank you Susan, I mean to say cone 011. Sorry... Ken
Susan Goldstein wrote:
> ----------------------------Original message----------------------------
> In a message dated 03/27/2000 3:06:51 PM Eastern Standard Time,
> kyancey1@tampabay.rr.com writes:
>
> << raku pottery. So far I've been
> using Mark's Copper Matt from the Branfman Book. Frit 3110 10%, Copper
> carb 90%, Iron Oxide 5%. I fire in a fiber lined oil drum in oxidation
> to cone 11. >>
>
> I never heard of firing raku to cone 11. Is this a mistake?
>
> Susan
Susan Goldstein on wed 29 mar 00
When you say flash the pot I am assuming you mean to uncover it and let it
flame up. How long do you keep it this way before recovering?
Susan
Sharon31 on wed 29 mar 00
I use this glaze, I found in the collection of raku glazes preparedby
Dewitt Gimblet (dewitt@realtime.com). This specific glaze does not need
burnished piece!
Glaze name: Mr. King's Sculpture Raku
Cone: 07
Firing: Raku
Surface texture: Lichen
Color: Red to Green
Date: 07/19/98
Recipe: (Percent, Batch)
Frit 3110 100.00 100.00
-------- --------
Totals: 100.00 100.00
Also add:
Black copper oxide 400.00 400.00
Red iron oxide 25.00 25.00
Comments:
Comments: Glaze type: Raku (Reduction) Transparency: Opaque Visual texture:
very much mottled and variable Bubbles: Few Flow: Slight Durability:
Medium
Date: 03/31/97 Comments: Be aware of flaky underfired surface it can
often
give. *Variations: Try Cobalt in place of copper for an interesting
flaky blue
glaze. This glaze is almost bordering on a stain of sorts, and the
addition of a
boron source (e.g. Gerstley Borate) might make it more of a glaze per
se. I like
the odd, dry and aged look it gives large sculptural works. *How long
have you
been using this glaze? One year *Where is it used? Columbus Academy
ceramics dept. Cols. OH. *Where did this recipe come from? I formulated
it
myself (on accident) *What do you like most about this glaze?
aged/varied
surface texture. *Is this glaze reliable? Dependability varies in direct
proportion to the reliability of the person firing it. Overfire or
deeply underfire
and it's not so pretty. *Does this glaze tend to
craze/crawl/pinhole/etc.? Watch
out for flakes. *How do different firing temperatures/atmospheres affect
the
glaze? Tip: Reduce not only in postfire red., but also in the kiln
during last
twenty min of raku (close the damper, cut off primary air) *How does the
glaze
behave on different clay bodies? It likes groggy clay. Don't know too
much
about stoneware/high iron bodies for this glaze, though. NOT FOR USE ON
PORCELAIN (for whomever may raku Porcelain in the first place) *What
consistency should the glaze be for pouring/dipping? THICK *How thickly
should the glaze be applied to the pot? two to three thick, uneven,
coats is best.
*How does this glaze interact with other glazes? avoid much combination
with
glossy glazes. Good partner with copper matt. Try Post Pac Man from Jan.
'97
CM. *What is your kiln type and size? 3 cubic foot fiber and brick raku
top hat
kiln. Dual Venturi system. *How do you typically fire? One hour raku,
starting
at 3psi, and increasing at 1psi per 10 min until 9psi is reached. Ten to
twenty
min at end of firing is in med. red. Soak moderately at cone 06 or so.
*Do you
experience problems with the raw glaze? add bentonite to solve settling.
Otherwise, best advice is to mix fresh and firs soon thereafter,
otherwise dry
cracking results. *Any other comments? I want my electric kiln to fire
in
reduction. *GlazeBase recipe* Submitted by: Kevin King (kingx61@ibm.net)
Ice Cream Flavor: Vanilla
I used once copper carbonate instead of the oxide in the some amounts, Or
another time added some cobalt ox. the way you spread salt on food to make
it variable.
In this opportunity to thank Mr. King for making this interesting glaze A
good solution for burnishing lazy like me!
Ababi
sharon@shoval.org.il
http://www.israelceramics.org/main.asp?what=gallery.htm
http://clay.justnet.com/cgallery/asharon.htm
----- Original Message -----
From: Susan Goldstein
To:
Sent: Tuesday, March 28, 2000 09:17
Subject: Re: RAKU: Copper Matt Techniques
> ----------------------------Original message----------------------------
> In a message dated 03/27/2000 3:06:51 PM Eastern Standard Time,
> kyancey1@tampabay.rr.com writes:
>
> << raku pottery. So far I've been
> using Mark's Copper Matt from the Branfman Book. Frit 3110 10%, Copper
> carb 90%, Iron Oxide 5%. I fire in a fiber lined oil drum in oxidation
> to cone 11. >>
>
> I never heard of firing raku to cone 11. Is this a mistake?
>
> Susan
Cantello Studios on thu 30 mar 00
Not very long at all, and look out for the fire. As you open up the can the
flames may jump up some from the can some 5 feet so please keep out of the
way. The way I like to do it is one pot at a time, pull one out place in can
with one layer of news paper lined around the inside of the can. Put the pot
in and cover with lid . Then I close the kiln lid up I do this all by my
self, It seams to be the right timing .I like to get the pot up to about
1880 or so that way you won't louse much heat before you flash it. That's
the reason I do one pot at a time If you try to take them all you louse to
much heat and your color will not be there. You must work hot and fast to
make this glaze do its thing, its good to time your self if you want to get
the best look each time. Another thing you must remember is that all copper
mat will change over time, this recipe seem to work very good, one very nice
pot set in my studio for 3 years, out of direct sun light of course and I
sold it last year for 300 bills it was a very nice pot. I made sure that the
buyer knew all about copper matt and raku but they loved it as did I so its
gone. I feel you must always be truthful with your buyers, keep them Happy
and they will love you forever. Good Luck Chris.
Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.UKY.EDU]On Behalf
Of Susan Goldstein
Sent: Wednesday, March 29, 2000 1:57 PM
To: CLAYART@LSV.UKY.EDU
Subject: Re: RAKU: Copper Matt Techniques
----------------------------Original message----------------------------
When you say flash the pot I am assuming you mean to uncover it and let it
flame up. How long do you keep it this way before recovering?
Susan
Marcia Selsor on fri 31 mar 00
I use "dry alligator" similar or same as Peipenburg's recipe.
Bone Ash 2 cups
Gerstley Borate 4 cups
Neph. Syenite 1 cup
Copper Carbonate 1 cup
I use it very lightly -sprayed on or in a wash applied by brush. If
thicker it gives its namesake scaley surface.
I fire to ^06 or 1850 degrees F. Place pieces in straw. I find cold days
produce better colors. Minus 20 I get great blues and golds.
A flash while cooling sometimes gives brighter color and sometimes goes
green. It's raku! If you don't get what you want, try again.
Marcia in Montana
>
--
Marcia Selsor
selsor@imt.net
http://www.imt.net/~mjbmls
http://www.imt.net/~mjbmls/spain99.html
http://www.silverhawk.com/ex99/selsor/welcome.html
Tom Buck on sun 2 apr 00
No, Chris, ALL copper matts will NOT change with time if they are properly
formulated. Please see my article on Matt Lustres...it was published in
UK's Ceramic Review No. 159, May/June 1996. It also is available for
download at http://www.digitalfire.com
(under my name).
If, however, you are discussing the so-called dry-matts (80%
copper carbonate plus some frit - most commonly 3134 - then this is a
"wash" not a glaze. Kind of hard to make an alumino-silicate melt when
there's practically no silica present. So, yes, this surface will be
changed by atmospheric conditions in a typical household.
Perhaps it is advisable to tell a buyer that such a dry matt MAY
change with time. Also, one could treat the surface with a thin coat of
spray lacquer and keep the pot away from direct sunlight and preferably
in a cool room, thus extending the "shelf-life".
til later. Peace. Tom B.
Tom Buck ) tel: 905-389-2339 (westend Lake Ontario,
province of Ontario, Canada). mailing address: 373 East 43rd Street,
Hamilton ON L8T 3E1 Canada
| |
|
