Steve Slatin on wed 19 jul 06
Hank --
I like your thoughts very much, but wonder at the thought that it requires
Strontium or Barium to develop a green. My concerns have two bases,
one more theoretical -- copper oxide has a 'natural' green color that we
would expect to develop in many glazes even absent Sr or Ba, and the
other one practical -- my strongest green glaze has very little Sr and
no Ba at all.
Unity on the glaze (above the line only) is as follows --
Recipe Name: Jill's Grassy Matte
Cone: 6-8 Color: Green
Firing: Oxidation Surface: Glossy
Unity Oxide
.255 Na2O
.065 K2O
.082 MgO
.595 CaO
.003 SrO
1.000 Total
.409 Al2O3
.276 B2O3
.02 Fe2O3
2.55 SiO2
.001 TiO2
0 P2O5
6.2 Ratio
73.4 Exp
The Sr in this glaze comes from Gillespie Borate; years ago we made it with Gerstley Borate and I no longer have a piece in the glaze but I believe it was always a very strong green. (I just bought a bag of Gerstley, and may experiment with a batch with -- allegedly -- no Sr at all.)
Best wishes -- Steve Slatin
Hank Murrow wrote:
Oh my God, Marianne;
I have been waiting for this question for years! Well, it all depends
upon what you are looking for in a glaze. For example, if you are
looking for green from copper, there must be some barium or strontium
in the glaze, and probably some talc for the magnesia, and a mix of
potassium and sodium feldspars (your G200 and Neph Sye). And you will
likely need small amounts of zinc, whiting, gerstley Borate and clay.
Add 2.5% copper carbonate for the color. Copper just won't likely make
that lovely green color unless it is in a base such as I have
described. Now for copper blues, you will want that G200 spar
again(perhaps 60%), with lots (30%) of barium, and some clay (kaolin,
so the color will be pure) and zinc (I find that zinc helps to promote
the oxidized form of the copper). Say, 5% each. throw in 3_4% copper
carbonate and you are on your way. Even copper yellow is not
unreachable if you can fire to cone 10 Oxidation. Start with Neph Sye
at 75%, and add 5% each of Dolomite and Whiting, another 5% kaolin, 2%
zinc (see above), and round it out with 8% silica. Finally add 1.5%
copper carb for the elusive color. Must be on a very white body and not
too thick, and not too thin....touchy thing this copper yellow.
So you can see how as the base changes, the color response from copper
will change. Now throw in the atmosphere in the kiln.......all those
glazes are likely to go livery or red, depending on how melty they
are........ no greens or blues, let alone yellow.
If you were looking for a durable surface for dinnerware, your search
would concentrate on whiting, potassium feldspar, kaolin, and silica,
perhaps some talc as well. Wollastonite would be a good addition. What
you are looking for will drive your choices.
I know you are probably asking by now, "But Hank, how do you know what
makes these colors/changes/surfaces?" My answer is, "the collective
experience/theorizing/speculation of generations of potters and
chemists, some of whom have written their results down........ leavened
(since you have a gift for metaphor) with my own considerable
experience trying to achieve these colors and others."
And that's the Truth, as I see it.
Cheers, Hank
www.murrow.biz/hank
---------------------------------
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marianne kuiper milks on wed 19 jul 06
OK. Have a good laugh.
I took Glaze Calculation at Alfred last year from Bill Carty. Learned a TON.
Read. Studied the manual.
Took a glaze class (GlazeMaster) from John.
Lili has answered MANY, many questions.
But there is still one very basic one I do not understand and it is driving me (more) crazy.
I understand the lists of various chemicals used, basic categories, to make a glaze. I can even figure out the balance needed once I see the ingredients. BUT...
HOW does one know WHICH ingredients?
Let's say that colomn/type A has 1,2,3,4 or 5 (whiting, silica, whatever)
How do I know whether to choose 1,2 or 4?
Why does each recipe not have the same basic 3 or 4 ingredients and add others from then on (not counting the colorants) in order to "fill the requirements" for a stable glaze?
I see that, to make cookies, I need flower, butter, sugar, baking powder, flavoring. But I could use margarine, eggs, brown sugar or Pillsbury flower instead of Gold Medal. choc. flavoring instead of almond.
BUT WHY? What tells me to use one instead of the other?
Why use G200 instead of whatever?
I know there are 20/20/20/20/20 glazes. But that is not my point. I want to know about the other basic combinations. WHY.
I would really, really appreciate explanations. I cannot find this answer in my books, unless I am overlooking something.
I realize I can buy glazes or use other people's recipes. But I want to know why, whether I ever use the information or not.
Thank you!!!
Marianne.
---------------------------------
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Wayne Seidl on wed 19 jul 06
Marianne:
No one is laughing, dear.
I asked the same question a few years ago. One of the gurus on the list
told me it was "quite simple". (Please excuse the simplistic =
explanation:)
The reason the ingredients vary is because the clay BODY on which the =
glaze
will be used varies. Some bodies may have an abundance of silica, for
example, and the glaze will be able to take some from the body in its
bonding and/or glass forming process. The same goes for most of the =
other
ingredients. There must be a "match" between the glaze and the body, in
order to eliminate the worst of the problems, such as crazing or =
shivering,
etc. The glaze gurus can fill in the (huge) knowledge gaps I'm leaving =
here.
On some clay bodies for example, you might have to use a Kona spar in =
the
glaze, where on others a Kona would exacerbate a problem. "It all =
depends"
on what is _in_ the spar being used _in relation_ to the ingredients in =
the
body, and vice versa. =20
That's why the motto has long been: test, test, test.
What works for me and mine won't solve the problems of you and yours.
What tells you which to use is the testing. Make 100g batches of glaze
using each of the types, or resolve to stick to one only, and adapt
everything else to fit.
Sorry if that sounds condescending. Not meant. It starts with a formula =
or
recipe, goes to a calculation program, and all comes down to trial and =
error
.
Hope it helps,
Wayne Seidl
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of marianne =
kuiper
milks
Sent: Wednesday, July 19, 2006 1:15 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: But I STILL don't get it! (glaze questios)
OK. Have a good laugh.
I took Glaze Calculation at Alfred last year from Bill Carty. Learned a
TON.
Read. Studied the manual.
Took a glaze class (GlazeMaster) from John.
Lili has answered MANY, many questions.
But there is still one very basic one I do not understand and it is =
driving
me (more) crazy.
I understand the lists of various chemicals used, basic categories, to =
make
a glaze. I can even figure out the balance needed once I see the
ingredients. BUT...
HOW does one know WHICH ingredients?
Let's say that colomn/type A has 1,2,3,4 or 5 (whiting, silica, =
whatever)
How do I know whether to choose 1,2 or 4?
Why does each recipe not have the same basic 3 or 4 ingredients and add
others from then on (not counting the colorants) in order to "fill the
requirements" for a stable glaze?
I see that, to make cookies, I need flower, butter, sugar, baking =
powder,
flavoring. But I could use margarine, eggs, brown sugar or Pillsbury =
flower
instead of Gold Medal. choc. flavoring instead of almond.
BUT WHY? What tells me to use one instead of the other?
Why use G200 instead of whatever?
I know there are 20/20/20/20/20 glazes. But that is not my point. I =
want to
know about the other basic combinations. WHY.
I would really, really appreciate explanations. I cannot find this =
answer
in my books, unless I am overlooking something.
I realize I can buy glazes or use other people's recipes. But I want to
know why, whether I ever use the information or not.
Thank you!!!
Marianne.
Elizabeth Priddy on wed 19 jul 06
I see that, to make cookies, I need flower, butter,
sugar, baking
powder, flavoring. But I could use margarine, eggs,
brown sugar or
Pillsbury flower instead of Gold Medal. choc.
flavoring instead of almond.
BUT WHY?
_____________________
Because cake flour, soy plour, unbleached flour,
self-rising flour and whole wheat flour, while all
being flour, will each behave slightly differently in
a recipe. You would certainly not use whole wheat
flour to make a delicate cake due to the particle
size, and the inclusion of husk bits.
Like Gerstley Borate that was dug up and ground versus
synthetic Gerstley substitute, each manufacturer has
its own formula, but it is all Gerstley by name.
Anyone can tell you that the micro-ingredients matter
as well as the "grind" or milling of the components.
Even the hardness or softness of your water will make
a difference.
Look to the archive on gerstley substitutions and you
will see WHY. The rest of your answer is work for
you.
Elizabeth Priddy
Beaufort, NC - USA
http://www.elizabethpriddy.com
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Hank Murrow on wed 19 jul 06
On Jul 19, 2006, at 10:14 AM, marianne kuiper milks wrote:
> OK. Have a good laugh.
> I took Glaze Calculation at Alfred last year from Bill Carty. Learned
> a TON.
> Read. Studied the manual. Took a glaze class (GlazeMaster) from John.
> Lili has answered MANY, many questions.
> But there is still one very basic one I do not understand and it is
> driving me (more) crazy.
>
> HOW does one know WHICH ingredients?
> Why use G200 instead of whatever?
Oh my God, Marianne;
I have been waiting for this question for years! Well, it all depends
upon what you are looking for in a glaze. For example, if you are
looking for green from copper, there must be some barium or strontium
in the glaze, and probably some talc for the magnesia, and a mix of
potassium and sodium feldspars (your G200 and Neph Sye). And you will
likely need small amounts of zinc, whiting, gerstley Borate and clay.
Add 2.5% copper carbonate for the color. Copper just won't likely make
that lovely green color unless it is in a base such as I have
described. Now for copper blues, you will want that G200 spar
again(perhaps 60%), with lots (30%) of barium, and some clay (kaolin,
so the color will be pure) and zinc (I find that zinc helps to promote
the oxidized form of the copper). Say, 5% each. throw in 3_4% copper
carbonate and you are on your way. Even copper yellow is not
unreachable if you can fire to cone 10 Oxidation. Start with Neph Sye
at 75%, and add 5% each of Dolomite and Whiting, another 5% kaolin, 2%
zinc (see above), and round it out with 8% silica. Finally add 1.5%
copper carb for the elusive color. Must be on a very white body and not
too thick, and not too thin....touchy thing this copper yellow.
So you can see how as the base changes, the color response from copper
will change. Now throw in the atmosphere in the kiln.......all those
glazes are likely to go livery or red, depending on how melty they
are........ no greens or blues, let alone yellow.
If you were looking for a durable surface for dinnerware, your search
would concentrate on whiting, potassium feldspar, kaolin, and silica,
perhaps some talc as well. Wollastonite would be a good addition. What
you are looking for will drive your choices.
I know you are probably asking by now, "But Hank, how do you know what
makes these colors/changes/surfaces?" My answer is, "the collective
experience/theorizing/speculation of generations of potters and
chemists, some of whom have written their results down........ leavened
(since you have a gift for metaphor) with my own considerable
experience trying to achieve these colors and others."
And that's the Truth, as I see it.
Cheers, Hank
www.murrow.biz/hank
www.murrow.biz/hank
Daniel Semler on wed 19 jul 06
Hi Marianne,
I posted an example of trying to do this sort of thing - selecting
ingredients
and actually saying why. Check this archive entry and there is a link to my
website
.
But as Hank's post points out its about the iteractions between materials and
what they do in different sorts of glazes. Mimi Obstler's book Out of
the Earth
Into the Fire has an interesting take on this. Look at Robin Hopper's Ceramic
Spectrum for the colour angle. There are a ton of interactions. The book by
Richard Eppler and Mimi Obstler (Understanding Glazes) gives examples
of making
glazes and why you'd choose one material over another. This is what
gave me the
idea to do my glaze in the above post.
Sometimes it doesn't matter much. Sometimes its a big deal. Depends. In the
end, calculation or not, its about the materials and how they interact in a
particular environment - all of them - body, glaze, kiln atmosphere, cone
etc...
Thx
D
Hank Murrow on thu 20 jul 06
On Jul 19, 2006, at 10:30 PM, Steve Slatin wrote:
> Hank --
>
> I like your thoughts very much, but wonder at the thought that it
> requires
> Strontium or Barium to develop a green.
Dear Steve;
I was referring to a matt green from copper, not a gloss green, such as
the currently popular Oribe types, and all my glazes are at cone 10,
whether oxidation or reduction. This matt green has color varying from
light jade to deep turquoise, depending upon strength of the copper
addition and the flux constituents.
Cheers, Hank
www.murrow.biz/hank
Susan Coville on thu 20 jul 06
Hi Marianne,
I often wrestle with this same question! Over time , through experimentation and necessity (i.e. don't have enough spodumene left to finish this glaze mix and can't buy anymore! Substitute another mineral, adding litium carb, sorta works, but not quite.... etc.)
Each of the materials we use for our glazes/clays come from the ground. I was once told variations were a given in ceramic materials, since we don't have a large population and our materials are not as quality controlled as other industry needs. Hence, other impurities are in our raw materials.
And each of the list you suggested (1,2,3,4 or 5) each have what I call their own personality. Or impurities. And whether you choose 1, 3 + 5 or 1, 2 + 4 each will yield a different result merely due to the slight variations in each componets personality and how well 'they play together', or combine in the melt. We must not forget the variations in kilns and firing process and the atmosphere and etc and etc...
I find it one of the most fascinating, enjoyable and oftimes frustrating part of the ceramics journey!
You could probably spend a great deal of time in study on this thermodynamic topic of the refractory materials/process and not completely exhaust the combinations or results!
I always rely on my intution a great deal when creating new glazes and do lots of testing, including when I get a brand new bag of material, just to see what has been mined this time.
Have fun ! Susan
marianne kuiper milks wrote:
OK. Have a good laugh.
I took Glaze Calculation at Alfred last year from Bill Carty. Learned a TON.
Read. Studied the manual.
Took a glaze class (GlazeMaster) from John.
Lili has answered MANY, many questions.
But there is still one very basic one I do not understand and it is driving me (more) crazy.
I understand the lists of various chemicals used, basic categories, to make a glaze. I can even figure out the balance needed once I see the ingredients. BUT...
HOW does one know WHICH ingredients?
Let's say that colomn/type A has 1,2,3,4 or 5 (whiting, silica, whatever)
How do I know whether to choose 1,2 or 4?
Why does each recipe not have the same basic 3 or 4 ingredients and add others from then on (not counting the colorants) in order to "fill the requirements" for a stable glaze?
I see that, to make cookies, I need flower, butter, sugar, baking powder, flavoring. But I could use margarine, eggs, brown sugar or Pillsbury flower instead of Gold Medal. choc. flavoring instead of almond.
BUT WHY? What tells me to use one instead of the other?
Why use G200 instead of whatever?
I know there are 20/20/20/20/20 glazes. But that is not my point. I want to know about the other basic combinations. WHY.
I would really, really appreciate explanations. I cannot find this answer in my books, unless I am overlooking something.
I realize I can buy glazes or use other people's recipes. But I want to know why, whether I ever use the information or not.
Thank you!!!
Marianne.
---------------------------------
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Ron Roy on thu 20 jul 06
Hi Marianne,
It will help if you have the analysis of some of the materials we use -
there are some in section F of our book for instance - many of the texts we
use have materials analysis - what is even more desirable are specific
analysis - from the mine - for each material.
If you are starting to make a glaze and you want to start with some Sodium
and potassium oxides - you will see if you look at the analysis of
materials - where those two are - in this case Feldspar, Neph Sy or frits.
You will probably decide to use the spars you have - they are mostly the
same anyway so unless you have a specific requirement (like a chun glaze)
just use what you have.
You will need some Calcium - most would use wollastonite or whiting - how
to choose?
Whiting is the most common source CaO - some say wollastonite is better
because there is hardly any LOI (loss on ignition) and it helps melting
because it's already combined with silica - but it costs more - and
sometimes you can't use all the SiO2 that comes with it.
You have glaze calculation software - why not do some experiments using
whiting in glaze and wollastonite in another - and find out if there is any
difference?
It is hard to generalize about this - you have to keep thinking - what cone
will I be firing to - maybe spar is not the best thing to use at cone 6 -
at least not the same amount as at cone 10 - because there is a lot of
alumina and silica that comes along with that KNaO.
I think it is safe to say most potters use the materials they can get from
their supplier. There are so many different materials these days we suffer
from the abundance.
If you can see the analysis of the materials you are thinking of using -
you will be able to make appropriate decisions.
In my glaze course book there are 3 pages of analysis - including frits and
clays - I can't imagine teaching the subject without that information.
RR
> I understand the lists of various chemicals used, basic categories, to
>make a glaze. I can even figure out the balance needed once I see the
>ingredients. BUT...
> HOW does one know WHICH ingredients?
> Let's say that colomn/type A has 1,2,3,4 or 5 (whiting, silica, whatever)
> How do I know whether to choose 1,2 or 4?
> Why does each recipe not have the same basic 3 or 4 ingredients and add
>others from then on (not counting the colorants) in order to "fill the
>requirements" for a stable glaze?
>
> I see that, to make cookies, I need flower, butter, sugar, baking powder,
>flavoring. But I could use margarine, eggs, brown sugar or Pillsbury
>flower instead of Gold Medal. choc. flavoring instead of almond.
> BUT WHY? What tells me to use one instead of the other?
> Why use G200 instead of whatever?
>
> I know there are 20/20/20/20/20 glazes. But that is not my point. I want
>to know about the other basic combinations. WHY.
> I would really, really appreciate explanations. I cannot find this answer
>in my books, unless I am overlooking something.
> I realize I can buy glazes or use other people's recipes. But I want to
>know why, whether I ever use the information or not.
>
> Thank you!!!
> Marianne.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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