nancee meeker on sun 2 jun 96
Can anyone suggest ways to "fix or repair" Raku glazes made with gerstley
borate?
I have always screened the glazes several times to sort of un-gel them so
that they can be poured, but several now seem to have too much water in
them (none on top), so that when one dips or pours the glaze several
things seem to happen. The glazes----- don't dry for ages -----go on too
thin-------or crack into "alligator" fissures when dry. I would really
like to not have to throw them all out and start over............TIA.
Nancee Meeker Studio and Gallery
169 Kelly St.
Rhinecliff, NY 12574
tel 914-876-3119
fax 914-876-3118
meeker@nextstep.net
Scott Finney on tue 4 jun 96
I've found that 50% gerstley borate and 50% nephline synite is a
wonderful raku glaze base. Rather than screening the mixture, I use
a blender and use directly. Try it you'll probably like it.
regards,
Scott
Burtt on sat 13 feb 99
Three tries and I'm stumped. I am working with a glaze called Blue
Hawaiian Raku, which I got from CM. So, I'm hoping others are familiar
with it. Out of three tries, it has worked for me only once and then I
got a nice pot with copper flashings in a dark blue background. The two
other times, I get a dark black/blue ugly covering with tiny crackling
throughout and very little copper.
I am trying to do this raku in an electric kiln. The first two tries
I fired to cone 04. Then I reduce in a trash can filled with newspaper
strips. A friend a fellow potter looked at the crackled mess and said I
was firing two high, so Friday I fired to cone 06. Failure again.
This is really my first efforts at raku in an electric kiln. Are
there special tricks that I am missing? It takes my kiln about an hour
and a half to reach 06; is that a problem with the raku process?
If I had not had the one success, I would blame the glaze. BTW, it is
a simple glaze: 80 percent Gerstley and 20 percent bone ash; then Tin
Oxide, 1.3; copper carb, 5.0; and cobalt oxide, 2.5.
Any help will be greatly appreciated.
Steve Burtt...
PurpleLama@aol.com on sun 14 feb 99
Hi,
I don't know whether I have used the glaze recipe that you are using. My notes
are buried in storage right now. However, when I lived back in Baltimore (up
until 7 weeks ago), I, too, did raku in an electric kiln (a small one). I
would have to check my notes, but I think that an hour and a half to get to
cone 06 sounds about right. Rather than using a cone after my first load, I
just eye-balled the glazes (wearing goggles) and pulled the pieces when the
glaze looked about right. I made sure that one of the pieces in each load had
a clear glaze on it and that is what I used to determine when it was time to
pull the pieces. I reduced in trash cans filled with shredded paper (from my
office). I also lined the rim of the trash cans with wet newspaper to better
seal them. I found that I got better copper flashing when I pulled the pieces
quickly from the kiln and put them in the trash cans. Usually I did the whole
process by myself. I saved the pieces with the clear glaze for last. I found
that they cracked and smoked better after they had been exposed to more air.
Shula
who lives in sunny LA but spent the day in San Diego so that my lab could play
at the beach. She had a wonderful time and so did I.
Burtt on mon 15 feb 99
Hi Shula,
Thanks so much for your reply to my raku problem. I think I have
isolated my problem. I was under the mistaken impression that the flames
made better copper flashings, so I was playing with the pot in the
flames for several minutes before ever closing it up in reduction. From
your's and other replies, I find that the pot needs to go quickly to the
reduction chamber.
I have not refired yet, but I am sure I will get a much different
result this time.
Again, thanks for your help.
Steve Burtt
Ocean Springs, Mississippi...on the Gulf Coast.
Tracey Duivestein on sun 31 dec 06
Dear Clayarters
I have been reading the Clayart forum for several months now and am =
still amazed at all the valuable information available and all the =
advice fellow potters are willing to dispense.
I have done several raku firings in a group setting, and have just =
started on my own, experimenting with new glazes, reduction times, =
methods, etc. Three new glazes have just peeled or powdered off my work =
when the kiln reaches 500 C, despite using different clay bodies, =
changing glaze thickness (from thin cream to water) and firing regimes =
(fast, slow, moderate - in a gas kiln). The three glazes are Revised =
Molly Blanding, Lubbcock Red Black Blue and Rainbow, and the only common =
factor in all 3 is Colemanite (60%, 70% & 40% respectively). Is South =
African Colemanite very different to the US one, and does anyone have =
any suggestions to rescue these glazes. =20
Unfortunately I have not been able to source Gerstly Borate in South =
Africa, so my glaze selection tends to be fairly limited as I am not yet =
very comfortable with substitutions. Also, can someone help me the =
breakdown of South African Frits ( FSB 757, FSB 656, F510 & Glazecor =
20306G L/L, 1601G L/Bisilicate & 3180).
Many thanks in advance from a very hot & humid Durban and may 2007 be =
the best yet
Tracey Duivestein
tracey@premieronline.co.za
Marcia Selsor on sun 31 dec 06
On Dec 31, 2006, at 2:15 AM, Tracey Duivestein wrote:
> Dear Clayarters
>
> I have been reading the Clayart forum for several months now and am
> still amazed at all the valuable information available and all the
> advice fellow potters are willing to dispense.
>
> I have done several raku firings in a group setting, and have just
> started on my own, experimenting with new glazes, reduction times,
> methods, etc. Three new glazes have just peeled or powdered off my
> work when the kiln reaches 500 C, despite using different clay
> bodies, changing glaze thickness (from thin cream to water) and
> firing regimes (fast, slow, moderate - in a gas kiln). The three
> glazes are Revised Molly Blanding, Lubbcock Red Black Blue and
> Rainbow, and the only common factor in all 3 is Colemanite (60%,
> 70% & 40% respectively). Is South African Colemanite very
> different to the US one, and does anyone have any suggestions to
> rescue these glazes.
>
> Unfortunately I have not been able to source Gerstly Borate in
> South Africa, so my glaze selection tends to be fairly limited as I
> am not yet very comfortable with substitutions. Also, can someone
> help me the breakdown of South African Frits ( FSB 757, FSB 656,
> F510 & Glazecor 20306G L/L, 1601G L/Bisilicate & 3180).
>
> Many thanks in advance from a very hot & humid Durban and may 2007
> be the best yet
>
> Tracey Duivestein
> tracey@premieronline.co.za
>
Tracey,
I had two plaques have their glaze crawl right off ot them This is
after hundres of pieces with the same glaze. I think I had sanded the
surface smooth with a diamond pad. I think the residue caused the
crawling in that case. Other than that, I don't know. I have taught
many raku workshops and never seen that happen. I use a sprayed on
glaze with gerstley borate.
Marcia Selsor
http://marciaselsor.com
Wally on mon 1 jan 07
Hello Tracey,
I would suggest to completely abandon the use of colemanite or
borocalcite in raku glazes at such high percentage.
Both minerals contain chemical-bound water that decomposes around
500-600=B0 Celcius, and tends to pulverise the glaze, if the balance
with other glazecomponents gets too high.
Done a lot of experiments with these minerals in my earlier efforts to
find an equivalent for gerstley borate, and saw all test-samples
really crushing up, disintegrating and decomposing, clearly visible
through the peephole, as from 500=B0 Celcius upwards.
Even when the colemanite and borocalcite were calcined beforehand, the
results were about the same.
One solution for you would be to get some gerstley borate shipped by
post from the US.....
I know the freight charges are quite expensive, but it is really worth
it, considering that you don't really need that much dry glazematerial
for a single glazelayer, and the cost of materials in regard to the
cost of one's workhours is allmost neglectable.
I don't know about South African frits or minerals, but a good
starting point for experiments to formulate a smooth dependable
rakuglaze could be 75% hi-alkaline low-firing frit, and 25% of fine
low-fire feldspar, preferably nepheline syenite.
Wally.
Schoten, Belgium
www.wallyasselberghs.be
--- In clayart@yahoogroups.com, Tracey Duivestein wrote:
>
> Dear Clayarters
>
> I have been reading the Clayart forum for several months now and am
still amazed at all the valuable information available and all the
advice fellow potters are willing to dispense.
>
> I have done several raku firings in a group setting, and have just
started on my own, experimenting with new glazes, reduction times,
methods, etc. Three new glazes have just peeled or powdered off my
work when the kiln reaches 500 C, despite using different clay bodies,
changing glaze thickness (from thin cream to water) and firing regimes
(fast, slow, moderate - in a gas kiln). The three glazes are Revised
Molly Blanding, Lubbcock Red Black Blue and R yainbow, and the only
common factor in all 3 is Colemanite (60%, 70% & 40% respectively).
Is South African Colemanite very different to the US one, and does
anyone have any suggestions to rescue these glazes.
>
> Unfortunately I have not been able to source Gerstly Borate in South
Africa, so my glaze selection tends to be fairly limited as I am not
yet very comfortable with substitutions. Also, can someone help me
the breakdown of South African Frits ( FSB 757, FSB 656, F510 &
Glazecor 20306G L/L, 1601G L/Bisilicate & 3180).
>
> Many thanks in advance from a very hot & humid Durban and may 2007
be the best yet
>
> Tracey Duivestein
> tracey@...
>
>
___________________________________________________________________________=
___
> Send postings to clayart@...
>
> 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@...
>
John Britt on mon 1 jan 07
Tracey,
Try this :
RAKU BLUE
Ferro 3134 27.40
Pemco P-25 42.50
Silica 14.00
Lithium Carbonate 9.80
EPK Kaolin 6.30
Copper Carbonate 4.50
You will have to find local frits and substitute. Keep it loose and just
try what you have. You will find a solution without gerstely borate.
Hope it helps,
John Britt
www.johnbrittpotteryc.om
Alisa Liskin Clausen on tue 2 jan 07
On Mon, 1 Jan 2007 21:32:17 -0500, John Britt wrote:
>Tracey,
>
>Try this :
>
>RAKU BLUE
>
>Ferro 3134 27.40
>Pemco P-25 42.50
>Silica 14.00
>Lithium Carbonate 9.80
>EPK Kaolin 6.30
>
>Copper Carbonate 4.50
>
>You will have to find local frits and substitute. Keep it loose and just
>try what you have. You will find a solution without gerstely borate.
>
>Hope it helps,
>
>John Britt
>www.johnbrittpotteryc.om
>
When I moved from NJ, America to Aabenraa, Denmark (say that with a
herring in your throat!) I thought that I could not make any glazes
without the Gerstley Borate I grew up on.
That is what initially prompted the glaze testing in me.
However, the best lesson I have learned is: ta dah,
learn and use your local materials. Wally is a great Raku artist. With
due repect, I would not yearn for any materials that need to be shipped
from remote parts of the world.
I am sure you have high boron frits in S.A. I know you do, because Tony
Matens, another Durbaneser, makes some nice glazes. Do you know her? She
has long left the list, but her friend Joan checks in occasionally. I
remember the carosoul by the sea in Durban. Hot, hot, hot!
Anyway, I would also leave Colominte alone. I used it a lot to try to get
it to sub. for G.B. All of my tests over 20% were not good. In Raku, you
only need a melt at low temp. So, you can make loads of glazes with 100 %
high Boron Frit. I add 10% Kaolin to give it a little more teeth and 10
Barium because I think the color response from Cu. and Fe is better with
the Barium.
But in fact, 100% high Boron frit is a Raku glaze. You will not see it
pop off the pot with an average application thickness, but you may, as
said, might want to stiffen it up with a little bit of clay.
Best regards, Alisa in Denmark
Steve Mills on tue 2 jan 07
Dear Tracey,
I absolutely agree with Wally; Colemanite is a beast of a material, and
no substitute for GB. However I wouldn't recommend you import any GB,
rather I would follow his suggestion of sourcing a locally obtainable
Hi-Alkaline Frit. For me this has been the most reliable basic Frit, up
against a plethora of seductive sounding recipes. My Basic is similar:
85 parts by weight Hi-Alk Frit with 15 parts China Clay (Kaolin) this
can be modified in so many ways by the addition of all sorts of other
materials and still gives excellent colour response with a maturing
temperature of +/- 1000oC=20
Steve=20
Bath
UK
> -----Original Message-----
> From: Wally [mailto:corneel51@YAHOO.COM]
> Sent: 01 January 2007 11:45 PM
> Subject: Re: Raku Glaze Problem
>=20
> Hello Tracey,
>=20
> I would suggest to completely abandon the use of colemanite or
> borocalcite in raku glazes at such high percentage.
> Both minerals contain chemical-bound water that decomposes around
> 500-600=B0 Celcius, and tends to pulverise the glaze, if the balance
> with other glazecomponents gets too high.
> Done a lot of experiments with these minerals in my earlier efforts to
> find an equivalent for gerstley borate, and saw all test-samples
> really crushing up, disintegrating and decomposing, clearly visible
> through the peephole, as from 500=B0 Celcius upwards.
> Even when the colemanite and borocalcite were calcined beforehand, the
> results were about the same.
>=20
> One solution for you would be to get some gerstley borate shipped by
> post from the US.....
> I know the freight charges are quite expensive, but it is really worth
> it, considering that you don't really need that much dry glazematerial
> for a single glazelayer, and the cost of materials in regard to the
> cost of one's workhours is allmost neglectable.
>=20
> I don't know about South African frits or minerals, but a good
> starting point for experiments to formulate a smooth dependable
> rakuglaze could be 75% hi-alkaline low-firing frit, and 25% of fine
> low-fire feldspar, preferably nepheline syenite.
>=20
> Wally.
> Schoten, Belgium
> www.wallyasselberghs.be
>=20
William & Susan Schran User on wed 3 jan 07
On 1/2/07 6:34 PM, "Steve Mills" wrote:
> My Basic is similar:
> 85 parts by weight Hi-Alk Frit with 15 parts China Clay (Kaolin) this
> can be modified in so many ways by the addition of all sorts of other
> materials and still gives excellent colour response with a maturing
> temperature of +/- 1000oC
We've found a high alkaline or high sodium frit (such as Ferro frit 3110)
works well in this application. We've also made adjustments by adding
lithium carbonate to lower the melting temperature, but no more than 5%.
Years ago when folks were seeking a substitute for gertsley borate, we tried
a Dal Tile frit #439. Very low melting point allowing up to 20% additions of
kaolin or ball clay for suspension and adhesion to the pot. Unfortunately we
discovered that the frit was soluble! I understood, after contacting Dal
Tile, that they would reformulate, but never heard back.
I think if one examines various frits and seeks one with a fairly low
melting point, thus allowing additions of clay and still melting at desired
raku temperatures, this could result in some interesting discoveries.
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Tracey Duivestein on thu 4 jan 07
Dear Wally
Thank you for taking the time to explain what is happening with my raku=20
glazes. You describe the effects so well - just watching it all puff off=
(&=20
ruin the kiln shelf) was something else. I will ditch those glazes & sta=
rt=20
afresh .
Again, thanks for your advice
Best wishes
Tracey
----- Original Message -----=20
From: "Wally"
To:
Sent: Tuesday, January 02, 2007 1:44 AM
Subject: Re: Raku Glaze Problem
Hello Tracey,
I would suggest to completely abandon the use of colemanite or
borocalcite in raku glazes at such high percentage.
Both minerals contain chemical-bound water that decomposes around
500-600=B0 Celcius, and tends to pulverise the glaze, if the balance
with other glazecomponents gets too high.
Done a lot of experiments with these minerals in my earlier efforts to
find an equivalent for gerstley borate, and saw all test-samples
really crushing up, disintegrating and decomposing, clearly visible
through the peephole, as from 500=B0 Celcius upwards.
Even when the colemanite and borocalcite were calcined beforehand, the
results were about the same.
One solution for you would be to get some gerstley borate shipped by
post from the US.....
I know the freight charges are quite expensive, but it is really worth
it, considering that you don't really need that much dry glazematerial
for a single glazelayer, and the cost of materials in regard to the
cost of one's workhours is allmost neglectable.
I don't know about South African frits or minerals, but a good
starting point for experiments to formulate a smooth dependable
rakuglaze could be 75% hi-alkaline low-firing frit, and 25% of fine
low-fire feldspar, preferably nepheline syenite.
Wally.
Schoten, Belgium
www.wallyasselberghs.be
--- In clayart@yahoogroups.com, Tracey Duivestein wrote:
>
> Dear Clayarters
>
> I have been reading the Clayart forum for several months now and am
still amazed at all the valuable information available and all the
advice fellow potters are willing to dispense.
>
> I have done several raku firings in a group setting, and have just
started on my own, experimenting with new glazes, reduction times,
methods, etc. Three new glazes have just peeled or powdered off my
work when the kiln reaches 500 C, despite using different clay bodies,
changing glaze thickness (from thin cream to water) and firing regimes
(fast, slow, moderate - in a gas kiln). The three glazes are Revised
Molly Blanding, Lubbcock Red Black Blue and R yainbow, and the only
common factor in all 3 is Colemanite (60%, 70% & 40% respectively).
Is South African Colemanite very different to the US one, and does
anyone have any suggestions to rescue these glazes.
>
> Unfortunately I have not been able to source Gerstly Borate in South
Africa, so my glaze selection tends to be fairly limited as I am not
yet very comfortable with substitutions. Also, can someone help me
the breakdown of South African Frits ( FSB 757, FSB 656, F510 &
Glazecor 20306G L/L, 1601G L/Bisilicate & 3180).
>
> Many thanks in advance from a very hot & humid Durban and may 2007
be the best yet
>
> Tracey Duivestein
> tracey@...
>
>
_________________________________________________________________________=
_____
> Send postings to clayart@...
>
> 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@...
>
_________________________________________________________________________=
_____
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=20
melpots@pclink.com.
--=20
No virus found in this incoming message.
Checked by AVG Free Edition.
Version: 7.5.432 / Virus Database: 268.16.1/611 - Release Date: 2006/12/3=
1=20
12:47 PM
Tracey Duivestein on thu 4 jan 07
Thanks to all the wonderful people who have replied to my problem of =
raku glazes powdering off at 500 C. As Colemanite seems to be the =
culprit, I will ditch those ones & start again. Just as well I only mix =
small batches for testing..
Importing Gerstly Borate is not an option at present - the exchange rate =
is high, let alone shipping costs, so I will do some serious =
experimenting with local frits.=20
Out with the thinking cap & raku kiln - just as well there is no rain =
forecast & it's very, very hot
Best wishes
Tracey Duivestein
tracey@premieronline.co.za
Julene on fri 5 jan 07
When using borate frits in raku glazes, does one
have more problems with glazes that are mixed and
allowed to sit around? Are the frits able to
absorb more water causing more puffing up? Should
these older glazes be thrown out?
As it is great firing weather here, I am once
again tuning in a new woodfired raku kiln. Great
learning experince for woodfiring. I just did a
load with a 50/50 ( Frit 3134 and Gillespie
Borate) glaze that was left from a couple years
ago when I was last firing the old raku kiln. The
puffing of the glaze was remarkable.
Julene, in Wisconsin, where it is said a cold
front is coming, but is the 20's really a cold
front?
| |
|
