Autumn Downey on mon 15 jul 02
Thanks, Tony. I think this may help with a few glazes that are being
problematic. Is EPK best used for white and clear glazes then? Or why
would one use it? It seems more common in recipes than ball clay these days.
Autumn
At 06:55 PM 2002-07-15 -0700, you wrote:
>Autumn,
>
>Yes, ball clay sticks much better. Try substituing the kaolin with ball
>clay with 25% increments. You probably could substitute the kaolin with ball
>clay without affecting your glaze very much other than it shrinking better
>with you claybody.
>
>Thank you.
>
>Tony Ferguson
>Stoneware, Porcelain, Raku
>www.aquariusartgallery.com
>218-727-6339
>315 N. Lake Ave
>Apt 312
>Duluth, MN 55806
>
>
>
>----- Original Message -----
>From: "Autumn Downey"
>To:
>Sent: Monday, July 15, 2002 3:34 PM
>Subject: Ball clay vs EPK
>
>
>> Have been dealing with some glazes that don't adhere too well; they tend
>to
>> crack in drying and often crawl in firing.
>>
>> They do have a fair amount of EPK in them. A trip through the archives
>> suggests that ball clay is being favoured for good glaze adherance these
>> days. Is this a correct reading?
>>
>> Otherwise I have been trying to get the characteristics right through
>> flocculants or deflocculants and sometimes both!
>>
>> Thanks for any info.
>>
>> Autumn Downey
>> Yellowknife, NWT
>>
>>
>____________________________________________________________________________
>__
>> 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.
>>
>
>___________________________________________________________________________
___
>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.
>
>
Autumn Downey on mon 15 jul 02
Have been dealing with some glazes that don't adhere too well; they tend to
crack in drying and often crawl in firing.
They do have a fair amount of EPK in them. A trip through the archives
suggests that ball clay is being favoured for good glaze adherance these
days. Is this a correct reading?
Otherwise I have been trying to get the characteristics right through
flocculants or deflocculants and sometimes both!
Thanks for any info.
Autumn Downey
Yellowknife, NWT
Tony Ferguson on mon 15 jul 02
Autumn,
Yes, ball clay sticks much better. Try substituing the kaolin with ball
clay with 25% increments. You probably could substitute the kaolin with ball
clay without affecting your glaze very much other than it shrinking better
with you claybody.
Thank you.
Tony Ferguson
Stoneware, Porcelain, Raku
www.aquariusartgallery.com
218-727-6339
315 N. Lake Ave
Apt 312
Duluth, MN 55806
----- Original Message -----
From: "Autumn Downey"
To:
Sent: Monday, July 15, 2002 3:34 PM
Subject: Ball clay vs EPK
> Have been dealing with some glazes that don't adhere too well; they tend
to
> crack in drying and often crawl in firing.
>
> They do have a fair amount of EPK in them. A trip through the archives
> suggests that ball clay is being favoured for good glaze adherance these
> days. Is this a correct reading?
>
> Otherwise I have been trying to get the characteristics right through
> flocculants or deflocculants and sometimes both!
>
> Thanks for any info.
>
> Autumn Downey
> Yellowknife, NWT
>
>
____________________________________________________________________________
__
> 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.
>
Bacia Edelman on mon 15 jul 02
Autumn:
First, let me assure you that I am not a glaze guru.
However, when that problem has happened to my work,
I have tried assorted remedies. I think
calcining the EPK in a bisque kiln and using up to
half of the required clay in calcined form worked for me.
Good luck.
Bacia
At 04:34 PM 07/15/2002 -0600, you wrote:
>Have been dealing with some glazes that don't adhere too well; they tend to
>crack in drying and often crawl in firing.
>
>They do have a fair amount of EPK in them. A trip through the archives
>suggests that ball clay is being favoured for good glaze adherance these
>days. Is this a correct reading?
>
>Otherwise I have been trying to get the characteristics right through
>flocculants or deflocculants and sometimes both!
>
>Thanks for any info.
>
>Autumn Downey
>Yellowknife, NWT
>
>___________________________________________________________________________
___
>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.
>
Ababi on tue 16 jul 02
I pay 1/5 more to use EPK. This is not the point. the point is (so I think).
The clays : ball clay kaolin as well as the red clays contribute to the good suspension
of the glaze. You can try it this way, make any glaze use 50 feldspar and 50 frit frit
and apply it. Does it stick to the claybody well?
How is the slurry after a week? Hard rock!
This a demonstrating glaze is cone 0
DEMONSTRATION GLAZE1
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Cone deg.C. -
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
FRIT 3124 50.00
Custer feldspar 50.00
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Seger Weight%
KNO 0.438 12.75%
CaO 0.562 12.57%
Al2O3 0.426 17.29%
B2O3 0.436 12.09%
SiO2 1.893 45.31%
K2O 0.151 5.68%
Na2O 0.286 7.07%
Al:Si 4.44
Expan. 9.71
ST 324.97
It is a bad glaze but it is just to explain how any clay can improve it .
DEMONSTRATION GLAZE 2
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Cone deg.C. -
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
FRIT 3134 41.00
EPK Kaolin 27.00
FRIT 3110 27.00
Alumina Hydrate 4.00
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
Seger Weight%
KNO 0.445 9.70%
CaO 0.553 10.63%
MgO 0.002 0.03%
Al2O3 0.432 15.07%
P2O5 0.001 0.07%
B2O3 0.455 10.84%
SiO2 2.602 53.56%
TiO2 0.004 0.11%
K2O 0.024 0.76%
Na2O 0.421 8.94%
Al:Si 6.03
Expan. 8.82
ST 323.92
I did not work hard to make these two glazes identical. The point is :
Up to 30% clay is very good for the suspension.
Above 30% use calcined clay. I add some to the bisque firing and keep it in a different
shelf than the regular clay.
When do I use uncalcined clay were it has more than 30%? Crater glazes
Yours forever
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910/
---------- Original Message ----------
>Thanks, Tony. I think this may help with a few glazes that are being
>problematic. Is EPK best used for white and clear glazes then? Or why
>would one use it? It seems more common in recipes than ball clay these days.
>Autumn
>At 06:55 PM 2002-07-15 -0700, you wrote:
>>Autumn,
>>
>>Yes, ball clay sticks much better. Try substituing the kaolin with ball
>>clay with 25% increments. You probably could substitute the kaolin with ball
>>clay without affecting your glaze very much other than it shrinking better
>>with you claybody.
>>
>>Thank you.
>>
>>Tony Ferguson
>>Stoneware, Porcelain, Raku
>>www.aquariusartgallery.com
>>218-727-6339
>>315 N. Lake Ave
>>Apt 312
>>Duluth, MN 55806
>>
>>
>>
>>----- Original Message -----
>>From: "Autumn Downey"
>>To:
>>Sent: Monday, July 15, 2002 3:34 PM
>>Subject: Ball clay vs EPK
>>
>>
>>> Have been dealing with some glazes that don't adhere too well; they tend
>>to
>>> crack in drying and often crawl in firing.
>>>
>>> They do have a fair amount of EPK in them. A trip through the archives
>>> suggests that ball clay is being favoured for good glaze adherance these
>>> days. Is this a correct reading?
>>>
>>> Otherwise I have been trying to get the characteristics right through
>>> flocculants or deflocculants and sometimes both!
>>>
>>> Thanks for any info.
>>>
>>> Autumn Downey
>>> Yellowknife, NWT
>>>
>>>
>>____________________________________________________________________________
>>__
>>> 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.
>>>
>>
>>___________________________________________________________________________
>___
>>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.
>>
>>
>______________________________________________________________________________
>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.
Ron Roy on wed 17 jul 02
Hi Autumn,
Best to do this with calculation software - Ball clays have less alumina in
them than kaolins - so you need more Ball clay to get the same amount of
alumina.
Ball clays hace (always) more silica then kaolins so you need to take some
silica out of the glaze to compensate.
Send me the recipe and tell me what kaolin you are using and what ball
clays you have to sub in. I'll recommend the best ball clay to use and tell
you how much.
If anyone needs to know how to do this let me know and I will do an
explanation for you. Just let me know what ball clays you have and if it's
alright to do it here on ClayArt.
RR
>Have been dealing with some glazes that don't adhere too well; they tend to
>crack in drying and often crawl in firing.
>
>They do have a fair amount of EPK in them. A trip through the archives
>suggests that ball clay is being favoured for good glaze adherance these
>days. Is this a correct reading?
>
>Otherwise I have been trying to get the characteristics right through
>flocculants or deflocculants and sometimes both!
>
>Thanks for any info.
>
>Autumn Downey
>Yellowknife, NWT
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on wed 17 jul 02
Why do so many glazes call for Kaolin? All Kaolins are pretty much the same
from a chemical point of view - they all have about the same amount of
alumina and silica. The main differences are how much TiO2 and Fe2O3 they
bring to the mix.
On the other hand Ball clays vary widely.
So it is safer to assume you are getting the "right" formula if kaolin is
specified. If you publish a glaze with ball clay in it and wanted it to
travel better you would specify the ball clay and include the analysis -
then anyone could use any ball clay they had the analysis for and calculate
any changes necessary.
It's one of the reasons we published the analysis for all the materials for
all our glazes in Mastering Cone 6 Glazes.
RR
>Thanks, Tony. I think this may help with a few glazes that are being
>problematic. Is EPK best used for white and clear glazes then? Or why
>would one use it? It seems more common in recipes than ball clay these days.
>
>Autumn
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ned Ludd on wed 17 jul 02
Hi Ron
Your lucid explanation of the EPK - Ball Clay substitution issue is right on.
When you write:
>I'll recommend the best ball clay to use and tell
>you how much.
Please tell us more about those ball clay differences - which and
why? I'm intrigued. It's not like our main textbooks have anything to
say on this point.
Any reason OM-4 wouldn't cut it in a substitution? I've noticed that
for most American potters, Ball Clay = OM-4: it's practically a
definition.
Should we think twice about that, and how?
Thank you, Ron. Have a great summer!
best,
Ned
>Hi Autumn,
>
>Best to do this with calculation software - Ball clays have less alumina in
>them than kaolins - so you need more Ball clay to get the same amount of
>alumina.
>Ball clays hace (always) more silica then kaolins so you need to take some
>silica out of the glaze to compensate.
>
>Send me the recipe and tell me what kaolin you are using and what ball
>clays you have to sub in. I'll recommend the best ball clay to use and tell
>you how much.
>
>If anyone needs to know how to do this let me know and I will do an
>explanation for you. Just let me know what ball clays you have and if it's
>alright to do it here on ClayArt.
>
>RR
>
>>Have been dealing with some glazes that don't adhere too well; they tend to
>>crack in drying and often crawl in firing.
>>
>>They do have a fair amount of EPK in them. A trip through the archives
>>suggests that ball clay is being favoured for good glaze adherance these
> >days. Is this a correct reading?
> >Autumn Downey
> >Yellowknife, NWT
Autumn Downey on wed 17 jul 02
Hi Ron,
Thank you for replying.
Actually the glaze is your black #3, as follows, with bentonite. We did
drop the bentonite here at the Guild and I think that helps. I still have
a batch in my studio in Saskatchewan with it though, so hope I can keep my
information straight - as I tend to get confused between the two places!!
CUSTER FELDSPAR 22
WHITING 4
TALC 5
FRIT 3134 26
epk kaolin 17
FLINT 26
BENTONITE 2
IRON OXIDE RED 9
COBALT CARBONATE 2
Tom Buck wrote me that red iron is quite variable and may be the problem.
My sense of this is that it doesn't form a very good bond with the pot and
a little bang to the glaze or a drip cannot be touched up without a bare
spot resulting in the firing.
It's not alot of EPK, so maybe the high amount of silica and frit are the
reason that it doesn't adhere well - along with the iron?? I really think
local water makes alot of difference too.
I'd quite like to try some ball clay along with kaolin to see if it makes a
better bond. According to Tom, the glaze does not give problems elsewhere,
so maybe we just need to tweak it for here.
It's good to have a black glaze that we're not afraid to use on dinnerware.
We got your (and John's) book for the Guild and as you've likely heard from
other quarters, the slate blue is a really big hit!! Brought it home
yesterday to read through.
Thanks for your help.
Autumn
It'At 01:09 AM 2002-07-17 -0400, you wrote:
>Hi Autumn,
>
>Best to do this with calculation software - Ball clays have less alumina in
>them than kaolins - so you need more Ball clay to get the same amount of
>alumina.
>Ball clays hace (always) more silica then kaolins so you need to take some
>silica out of the glaze to compensate.
>
>Send me the recipe and tell me what kaolin you are using and what ball
>clays you have to sub in. I'll recommend the best ball clay to use and tell
>you how much.
>
>If anyone needs to know how to do this let me know and I will do an
>explanation for you. Just let me know what ball clays you have and if it's
>alright to do it here on ClayArt.
>
>RR
>
>>Have been dealing with some glazes that don't adhere too well; they tend to
>>crack in drying and often crawl in firing.
>>
>>They do have a fair amount of EPK in them. A trip through the archives
>>suggests that ball clay is being favoured for good glaze adherance these
>>days. Is this a correct reading?
>>
>>Otherwise I have been trying to get the characteristics right through
>>flocculants or deflocculants and sometimes both!
>>
>>Thanks for any info.
>>
>>Autumn Downey
>>Yellowknife, NWT
>
>Ron Roy
>RR#4
>15084 Little Lake Road
>Brighton, Ontario
>Canada
>K0K 1H0
>Phone: 613-475-9544
>Fax: 613-475-3513
>
>___________________________________________________________________________
___
>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.
>
>
Ababi on wed 17 jul 02
Hello Ned.
You have to read/buy a good materials book, there are several of them.
As I am a glaze addict not a glaze guru I shall explain you in simple way. Perhaps
Steven Branfman SBRANFPOTS@AOL.COM will offer you a list of books.
So How it go. When the earth was created there were mountains full with feldspar.
Than was wind and rain and time and sun, some of the rocks crumbled into white
clay, kaolin.
Again rain winter summer, the clay is taken to travel in the rivers, some iron is added,
some animals products, similar to kaolin, yet "dirtier" some more iron, as well as the
rotten plants, animals fish low quality beer ,all are improving the plasticity of the
kaolin that got new name:
BALL CLAY
The rest is in the books
Ababi Sharon
Glaze addict
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://members4.clubphoto.com/ababi306910/
---------- Original Message ----------
>Hi Ron
>
>Please tell us more about those ball clay differences - which and
>why?
>best,
>Ned
David Hewitt on thu 18 jul 02
Ball clays vary considerably, particularly in the amount of silica they
contain and they are always a lot higher in silica than with EPK or
China clay ( as we would use in the UK). To just talk of replacing EPK
with a Ball clay is not precise enough. Which one are you proposing to
use? In all cases you would need to make some change to the recipe. A
glaze program is the answer to achieving this.
As some examples of the variation in analyses of Ball clays, I have
included some examples on my web site under Pottery Techniques /
Transporting Recipes.
http://www.dhpot.demon.co.uk
David
--
David Hewitt
David Hewitt Pottery ,
7 Fairfield Road, Caerleon, Newport,
South Wales, NP18 3DQ, UK. Tel:- +44 (0) 1633 420647
FAX:- +44 (0) 870 1617274
Web site http://www.dhpot.demon.co.uk
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