wayneinkeywest on wed 14 jan 04
Ok, now I'm (more) confused.
I've been rummaging through the Archives,=20
getting lost, running down dead ends,=20
split and multiple threads and switchbacks,=20
compiling recipes and their additions,=20
modifications, and the arguments for=20
and against each of them. (Some of you are=20
QUITE adamant!) I've researched
the "best" replacement(s) for Gerstley Borate,
found the substitution equations for barium
vs strontium...gone crazy trying to decipher
the compositions of frits (some of which are
no longer with us)...all the fun stuff you kind folk
have all been through since around 1996=20
and before. (The archives start in '96 I believe.)
First:
Some of the recipes I would like to try
refer to "iron oxide" Ok, simple enough.
Sometimes RED iron oxide, sometimes
BLACK, sometimes YELLOW.
In a recipe calling for simply "iron oxide"
do I (willy-nilly) select a color based on
what would be closest to the color of the
glaze I'm trying for? Did the colors
come about recently, and there was only
ONE available previously? For all my
(lack of) experience with glaze, I do
recall that oxide of iron is usually BROWN
(it's called rust in other trades.)
Second question:
Same deal with Kaolins. GlazeMaster lists
a plethora of Kaolins; some recipes specify
only "kaolin".
Use whatever is hanging around? Go for a specific
type as is used in most other recipes (EPK)?
Match a kaolin to my particular clay body
(in my case Grolleg)?
Go ahead and laugh...the clay gods take=20
great delight in torturing newbies
and we do deserve it sometimes :>)
Would one of you be kind enough to=20
point me in the right direction before I start
to "test, test, test"
TIA
Wayne "I don't know it all yet" Seidl
Paul Herman on wed 14 jan 04
Hi Wayne,
Though not a guru, I'd use red Iron. Firing renders them all the same,
though black is a little higher Iron content. Black and yellow aren't
new.
For use in glazes, Kaolins are so similar you could use EPK or whatever
you have.
Happy mixing,
Paul Herman
Great Basin Pottery
423-725 Scott Road
Doyle, California 96109 US
potter@psln.com
----------
>From: wayneinkeywest
> First:
> Some of the recipes I would like to try
> refer to "iron oxide" Ok, simple enough.
> Sometimes RED iron oxide, sometimes
> BLACK, sometimes YELLOW.
> In a recipe calling for simply "iron oxide"
> do I (willy-nilly) select a color based on
> what would be closest to the color of the
> glaze I'm trying for? Did the colors
> come about recently, and there was only
> ONE available previously? For all my
> (lack of) experience with glaze, I do
> recall that oxide of iron is usually BROWN
> (it's called rust in other trades.)
>
> Second question:
> Same deal with Kaolins. GlazeMaster lists
> a plethora of Kaolins; some recipes specify
> only "kaolin".
> Use whatever is hanging around? Go for a specific
> type as is used in most other recipes (EPK)?
> Match a kaolin to my particular clay body
> (in my case Grolleg)?
>
> Go ahead and laugh...the clay gods take
> great delight in torturing newbies
> and we do deserve it sometimes :>)
>
> Would one of you be kind enough to
> point me in the right direction before I start
> to "test, test, test"
> TIA
> Wayne "I don't know it all yet" Seidl
william schran on thu 15 jan 04
Wayne wrote:>In a recipe calling for simply "iron oxide"
do I (willy-nilly) select a color based on
what would be closest to the color of the
glaze I'm trying for?<
>Go for a specific
type as is used in most other recipes (EPK)?
Match a kaolin to my particular clay body
(in my case Grolleg)?<
Any glaze calling for iron oxide without any more specifics - stick
with red iron oxide.
Any glaze calling for kaolin without any more specifics - stick with EPK*
* buy it by the full bag (50lb.), take out some and calcine it (fire
to bisque in open bowl).
Bill
Krista Peterson on thu 15 jan 04
>In a recipe calling for simply "iron oxide"
>do I (willy-nilly) select a color based on
>what would be closest to the color of the
>glaze I'm trying for?
In my experience, Red Iron Oxide is the most common iron oxide used so when a recipe says
just "iron oxide" I use red iron oxide. If the others are required they are usually specified.
Same thing with kaolin. EPK is the most common so when it is not specific I use EPK. Although
I don't think it's as important. I don't think you'll find that many differences between kaolins. When
I don't have any EPK around I'll use Helmer Kaolin(I think it has a touch more iron than EPK). And while we're
on the subject, same with ball clay. OM4 is the most common so if a recipe just says "ball clay" I use OM4.
Take care
Krista Peterson
John Hesselberth on thu 15 jan 04
On Wednesday, January 14, 2004, at 05:41 PM, wayneinkeywest wrote:
> In a recipe calling for simply "iron oxide"
> do I (willy-nilly) select a color based on
> what would be closest to the color of the
> glaze I'm trying for?
Hi Wayne,
I'm glad you got the part at the end (test, test, test) right. A lot of
us are a little sloppy when we write recipes down, but I would wager
most people mean red (RIO) when they just say iron oxide.
>
> Second question:
> Same deal with Kaolins. GlazeMaster lists
> a plethora of Kaolins; some recipes specify
> only "kaolin".
>
Again in the U.S and Canada most people use EPK as their standard
kaolin, but if you look at those compositions most are pretty similar.
So if you don't have EPK try Georgia or whatever and test, test, test.
It also depends on how much is in the recipe. If it is only 5-10% you
could probably substitute any kaolin. If it is 40%, well you might have
to be more cautious.
>
> Go ahead and laugh...the clay gods take
> great delight in torturing newbies
> and we do deserve it sometimes :>)
Well, they probably don't do this on purpose, but the open literature
is full of stuff like this. Lots of people have developed recipes over
the years. Some of them probably didn't even know what kind of kaolin
or whatever they were using, others were just more casual. Still others
may have realized it was such a small percentage it wouldn't really
make any difference. You will quickly get used to this kind of 'holes'
in the literature so don't get too uptight about it.
Regards,
John
>
> Would one of you be kind enough to
> point me in the right direction before I start
> to "test, test, test"
> TIA
> Wayne "I don't know it all yet" Seidl
>
> _______________________________________________________________________
> _______
> 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.
>
>
http://www.frogpondpottery.com
http://www.masteringglazes.com
Hank Murrow on fri 16 jan 04
On Jan 16, 2004, at 3:43 PM, karen gringhuis wrote:
> Whatever kaolin you chose, if the percentage hits
> around 20% or more, split it between your kaolin of
> choice and calcined kaolin. This is because kaolin
> shrinks when the glaze dries and thus can cause the
> glaze to peel off the pot. Calcined kaolin can
> alieviate this.
Karen is right again! Of course, that plastic kaolin can also create
marvellous crawl patterns in case your aesthetic embraces these. See
http://www.murrow.biz/hank/shino-pots.htm for examples, 26% in the
case of these.
Cheers, Hank in Eugene
David Hewitt on fri 16 jan 04
Wayne,
I very much sympathise with your problem. All too often the person
recording the recipe in the first place fails to be precise enough as to
what they have used. Also, all too few bother to give an analysis based
on their particular source of materials. You may not know in which part
of the world a recipe originated - except that if it includes Gerstley
Borate then North America if a fairly safe bet.
Others have indicated that in the absence of any further information
than just 'kaolin' then use EPK, but if you were looking at a UK recipe
the 'china clay' may have more silica than EPK and no CaO or Mgo.
Also I find that Ball clays vary very significantly and to just to
assume OM#4 could be a long way out.
You mention iron oxide, and I would agree that in the absence of
anything else assume that it is red iron oxide, but there is likely to
be a big difference between synthetic red iron and natural red iron
oxide. My supplier's synthetic red iron oxide contains 96% Fe2O3 and the
natural 75% Fe2O3 plus 13% SiO2 and 3% Al2O3. With Black Iron Oxide
there are even greater variables.
This whole question of 'Transporting' Recipes is, in my view, very
important, and I have tried to amplify on these arguments on my web site
under Pottery Techniques / 'Transporting' recipes and Raw Materials - Do
you know what you are buying.
http://www.dhpot.demon.co.uk
I don't know if this will help you with regard to your specific recipe,
but may I take this opportunity of trying to encourage the regular
inclusion of an analysis with every recipe. This does mean that one has
to have a glaze calculation program, but these do not cost much as is
also indicated on my web site.
Wishing you good testing,
David
In message , wayneinkeywest writes
>Ok, now I'm (more) confused.
>I've been rummaging through the Archives,
>getting lost, running down dead ends,
>split and multiple threads and switchbacks,
>compiling recipes and their additions,
>modifications, and the arguments for
>and against each of them. (Some of you are
>QUITE adamant!) I've researched
>the "best" replacement(s) for Gerstley Borate,
>found the substitution equations for barium
>vs strontium...gone crazy trying to decipher
>the compositions of frits (some of which are
>no longer with us)...all the fun stuff you kind folk
>have all been through since around 1996
>and before. (The archives start in '96 I believe.)
>First:
>Some of the recipes I would like to try
>refer to "iron oxide" Ok, simple enough.
>Sometimes RED iron oxide, sometimes
>BLACK, sometimes YELLOW.
>In a recipe calling for simply "iron oxide"
>do I (willy-nilly) select a color based on
>what would be closest to the color of the
>glaze I'm trying for? Did the colors
>come about recently, and there was only
>ONE available previously? For all my
>(lack of) experience with glaze, I do
>recall that oxide of iron is usually BROWN
>(it's called rust in other trades.)
>
>Second question:
>Same deal with Kaolins. GlazeMaster lists
>a plethora of Kaolins; some recipes specify
>only "kaolin".
>Use whatever is hanging around? Go for a specific
>type as is used in most other recipes (EPK)?
>Match a kaolin to my particular clay body
>(in my case Grolleg)?
>
>Go ahead and laugh...the clay gods take
>great delight in torturing newbies
>and we do deserve it sometimes :>)
>
>Would one of you be kind enough to
>point me in the right direction before I start
>to "test, test, test"
>TIA
>Wayne "I don't know it all yet" Seidl
--
David Hewitt
David Hewitt Pottery
South Wales UK
Web:- http://www.dhpot.demon.co.uk
karen gringhuis on fri 16 jan 04
Wayne -
Nobody "knows it all yet!" But as an Elder once said
to me "you're asking questions; that's good."
Whatever kaolin you chose, if the percentage hits
around 20% or more, split it between your kaolin of
choice and calcined kaolin. This is because kaolin
shrinks when the glaze dries and thus can cause the
glaze to peel off the pot. Calcined kaolin can
alieviate this.
=====
Karen Gringhuis
KG Pottery
Box 607 Alfred NY 14802
__________________________________
Do you Yahoo!?
Yahoo! Hotjobs: Enter the "Signing Bonus" Sweepstakes
http://hotjobs.sweepstakes.yahoo.com/signingbonus
iandol on sat 17 jan 04
Dear Wayne in Keywest,
Good questions. Shows you are searching for discrimination within the =
general knowledge available. Good way to get to some short cuts.
I will take your example of Kaolin. As a general ingredient in a clay =
body, one may be as good as another from the point of view of the =
elemental chemistry. But when it comes down to particle size this may =
have a profound effect on plasticity. So seek information about particle =
size and look at the fractional distribution graphs to enhance your =
knowledge and understanding of what is being.
Second point is when it is used as a glaze additive. In this situation =
it is the minor elements that are in the analysis which become =
influential. In particular residual Iron minerals and Titanium minerals =
and the balance between them can influence clarity and colour of certain =
glaze styles that have delicate hues
All the best with your search for enlightenment,
Ivor Lewis. Redhill, South Australia.
| |
|
