Terrance Lazaroff on fri 29 jun 01
Jeff;
The question you pose is going to be very difficult for anyone to answer
with certainty.
You should start to ask your self a set of questions when this happens. They
could be:
Am I using the same claybody as before;
did I bisque to the same temp/cone as before;
did I bisque in the same atmosphere as before;
did I use the same glaze that was prepared for previous firings;
when was the last time the glaze mixture was used;
was there any chance of contamination if it was a previous mixture;
did I check the glaze recipe to ensure it was copied correctly;
did I measure separately all my ingredients and recheck the weights before
mixing;
did I use the same amount of water in the mix as before and did I check the
density;
did I apply the glaze the same as before;
did the raku kiln fire the same as before, more oxidation, more reduction,
faster heat rise;
was the piece wet going into the kiln;
and, was the piece glazed at least 24 hours prior to firing?
All of these questions will help you determine what is going wrong.
Answering a question must begin with a question.
Terrance
BobWicks@AOL.COM on fri 29 jun 01
Jeff:
After you did your first bisque fire, did you protect your projects from dust
in the room? This often times does just what you describe. I might suggest
that you do another fire being certain that the bisque ware is not being
contaminated from room dust or dirt.
Robert Wicks, Prof Emeritus
Ravenson on fri 29 jun 01
Hi everyone I need a little help. For years I been using a Raku =
glaze called Blue silver. This is a nice little accent glaze that goes =
from a blue color to a metallic silver or ever metallic gold if it gets =
lots of reduction. Last night a friends and I did 4 or 5 loads of raku =
and in every one the blue sliver peeled off the pots, it did not do it =
to all the pots or even in all the places on the same pots, but in most =
places it did. You could look in the top of the kiln as it was going =
up and watch the glaze peeling off. In all the time I have used this =
glaze This is the first time I have ever seen it peel I have seen In run =
off but never peel. So the question does anyone have any idea why =
this happened and how to fix it. Here is the Glaze
BLUE SILVER RAKU GLAZE
Frit 3269 42.5
Frit 3134 27.4
Lithium Carb 9.8
EPK 6.3
Silica 14.0
Bentonite 2.0
add
silver nitrate 2.1
Soda Ash 1 Gram
Cobalt carb 1.1
CMC=20
now for some notes: this is the glaze exactly how I got it from my =
instructor. He very often left out the EPK,Bentonite, CMC,and the soda =
ash, he said that in his experience they did not seem to do much.
I have mixed this glaze in the past and used everything except the =
CMC(I did Not Have any On hand). That is what I did this last time also =
no CMC but Every thing else. I e-mailed my instructor and he said to =
try adding 3 grams of soda ash per 1000gr batch and to see it that =
helps, and to ask everyone on the list about it. Does anyone know what =
the soda ash is doing in this glaze and how it is going to stop the =
peeling or have any other ideas of how to stop the peeling.
Thank You=20
Jeff James
Ray Found on sat 30 jun 01
i'had this happen once when I put a glaze on thick and did not let it dry
completly before hitting the kiln, same thing, just watch it peel off in
little scales. I would think that letting it dry would do the trick, and
maybe add a few more % bentonite, it has always helped stick stuff down for
me.
Ray Found
PS- despaite al the reccomendations i hear to never add dry bemtonite to a
wet glaze, i have found that if I have the electric drill in there mixing,
and put the bentonite in slow, like dust it in, there is no problem.
Richard Jeffery on sat 30 jun 01
Terrance is right of course...
whilst you're working out how to do all of that, here's my experience, which
may or may not relate to yours -
I often use a silver nitrate glaze as a highlight. I have experienced
problems such as you describe when the glaze (both underlying and accent)
was not as dry as I would like (need to deliver...), and I fired too fast
(new fibre top hat kiln I had just built, before I worked out where the
brakes were). Like you, I could see the accent glaze peeling off. - this
had been made by the way by mixing, as usual, dissolved silver nitrate into
a commercial transparent raku glaze, so I don't think the glaze composition
was a factor for me.
Hope this helps
Richard
Bournemouth UK
www.TheEleventhHour.co.uk
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]On
Behalf Of Terrance Lazaroff
Sent: 30 June 2001 01:59
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Raku Glaze help
Jeff;
The question you pose is going to be very difficult for anyone to answer
with certainty.
You should start to ask your self a set of questions when this happens. They
could be:
Am I using the same claybody as before;
did I bisque to the same temp/cone as before;
did I bisque in the same atmosphere as before;
did I use the same glaze that was prepared for previous firings;
when was the last time the glaze mixture was used;
was there any chance of contamination if it was a previous mixture;
did I check the glaze recipe to ensure it was copied correctly;
did I measure separately all my ingredients and recheck the weights before
mixing;
did I use the same amount of water in the mix as before and did I check the
density;
did I apply the glaze the same as before;
did the raku kiln fire the same as before, more oxidation, more reduction,
faster heat rise;
was the piece wet going into the kiln;
and, was the piece glazed at least 24 hours prior to firing?
All of these questions will help you determine what is going wrong.
Answering a question must begin with a question.
Terrance
____________________________________________________________________________
__
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.
Clayhannie@AOL.COM on tue 18 may 04
Our Art Center has about 10 gallons of a couple of Raku glazes leftover from
last years Raku Day event. (We sell bisque, public glazes it and we fire it -
11th year)
They are not coming out as usual - not getting post reduction colors, even
though the firing, etc. is the same. Newly mixed glazes are OK. June 5 is the
day we need them
Is there anything we can do to salvage these? Or should we just make new
ones.
Copper Penny
Gerstley Borate 800
Cornwall Stone 200
Yellow ochre 80
Cu Oxide 20
Cobalt Ox. 10
Piepenberg Patina
Gerstley Borate 4 cups
Neph Syenite 3 cups
Bone Ash 2 cups
Copper Carb 1 cup
Also have the same problem with Hawaiian Blue, but I don't have the recipe
here at home.
Thanks,
Martha Griffith
clayhannie@aol.com
The Fine Line Creative Arts Center
St. Charles, IL 60175
Gary Ferguson on fri 21 may 04
I have found in general that Raku Glazes (esp ones with Gerstley Borate)
perform differently if they have been mixed with water and sit for a long
period of time. I now mix basically what I am going to use as one time.
I'm not sure there is anything you can really do - if you don't like how
they are performing now, I think I would cut my losses and mix up new
batches.
Gary Ferguson
Raku Clay Artist
Nampa, ID 83687
Raku Gallery at: http://www.garyrferguson.com
300+ Glaze Collection at: http://www.rakuglazes.com
Subscribe to Just Raku Newsletter at http://www.JustRaku.com
Just Raku Logowear at: http://www.cafepress.com/justraku
Got Raku? Wear it here: http://www.cafepress.com/gotraku
----- Original Message -----
From:
To:
Sent: Tuesday, May 18, 2004 7:20 AM
Subject: RAKU GLAZE HELP
> Our Art Center has about 10 gallons of a couple of Raku glazes leftover
from
> last years Raku Day event. (We sell bisque, public glazes it and we fire
it -
> 11th year)
> They are not coming out as usual - not getting post reduction colors, even
> though the firing, etc. is the same. Newly mixed glazes are OK. June 5 is
the
> day we need them
> Is there anything we can do to salvage these? Or should we just make new
> ones.
>
> Copper Penny
> Gerstley Borate 800
> Cornwall Stone 200
> Yellow ochre 80
> Cu Oxide 20
> Cobalt Ox. 10
>
> Piepenberg Patina
> Gerstley Borate 4 cups
> Neph Syenite 3 cups
> Bone Ash 2 cups
> Copper Carb 1 cup
>
> Also have the same problem with Hawaiian Blue, but I don't have the recipe
> here at home.
>
> Thanks,
> Martha Griffith
> clayhannie@aol.com
> The Fine Line Creative Arts Center
> St. Charles, IL 60175
>
>
____________________________________________________________________________
__
> 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.
Craig Dunn Clark on fri 21 may 04
Martha, I regularly use Pipenburs Alligator with about 1% cobalt carb in the
mix. I mix the glaze by mass. I have had five gallons or more on hand for
years. If the glaze has been setting awhile I will re-sieve it through both
a 50 and 80 mesh screen and then pour it back and forth between two buckets
ten times. Works consistently well for me. Same goes for a yellow crackle,
white crackle and a green crackle which will go opalescent at higher temp.
The last time I had difficulty getting the type of reduction that I was
after it was because the cans that I was using were past their, they leaked.
No proper seal/no decent reduction. Bought some new cans, used a sheet of
wet newspaper across the top right before closing the can and I can get that
bright copper penny look if I want.
Are you glazes maturing? If so then you may have the leakage problem or
perhaps the glazes have hardpanned and you just aren't getting them mixed up
well. Pour the glaze into a clean bucket and see if there is any muck in the
bottom of the old bucket. If there that is a potential candidate on which to
blame your glaze woes.
If you have a jiffy mixer, well worth purchasing if you don't, just pour a
little water over the top of any hard panned material and let the mixer do
the job. After that just pour it into the rest of the glaze, sieve twice,
mix by pouring, check your cans and you will hopefully have the reduction
effect that you are after.
Hope this helps
Craig Dunn Clark
619 East 11 1/2 st
Houston, Texas 77008
(713)861-2083
mudman@hal-pc.org
----- Original Message -----
From:
To:
Sent: Tuesday, May 18, 2004 8:20 AM
Subject: RAKU GLAZE HELP
> Our Art Center has about 10 gallons of a couple of Raku glazes leftover
from
> last years Raku Day event. (We sell bisque, public glazes it and we fire
it -
> 11th year)
> They are not coming out as usual - not getting post reduction colors, even
> though the firing, etc. is the same. Newly mixed glazes are OK. June 5 is
the
> day we need them
> Is there anything we can do to salvage these? Or should we just make new
> ones.
>
> Copper Penny
> Gerstley Borate 800
> Cornwall Stone 200
> Yellow ochre 80
> Cu Oxide 20
> Cobalt Ox. 10
>
> Piepenberg Patina
> Gerstley Borate 4 cups
> Neph Syenite 3 cups
> Bone Ash 2 cups
> Copper Carb 1 cup
>
> Also have the same problem with Hawaiian Blue, but I don't have the recipe
> here at home.
>
> Thanks,
> Martha Griffith
> clayhannie@aol.com
> The Fine Line Creative Arts Center
> St. Charles, IL 60175
>
>
____________________________________________________________________________
__
> 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.
| |
|
