Corinne Null on fri 9 jan 98
Many thanks for all the helpful responses on this thread. I've decided
that it's OK to use Dolomite and Talc and Rutile, and that I might do well
to stay away from Whiting and Magnesium Carbonate if I'm having pinholing
problems because of outgassing at high temps. (Have I got that right?) Tom
Buck was the walking encyclopedia on this one!
David Hendley pointed out the aspect of the amount of processing being a
large part of the expense of the purer ingredients. Louis Katz and Leslie
Norton observed that the more intimately involved ingredients behave better.
So, this puts me into another frame of mind. Can I make a list ingredients
that are "trouble, with a capital T" (and I don't mean for toxicity, I mean
for flaws)? So far I've got:
Whiting
Magnesium Carbonate
sometimes - neph sy - crazing
Anything else?
Can I make another list of "variable but useful" ingredients?
Gerstley Borate
Dolomite
Cornwall Stone
Somehow I thought the lists would be longer.
And, I still can't figure on the Bone Ash. Natural English or Synthetic?
Please correct my thinking again if I'm STILL out in left field! I keep
peeling away at this glaze onion, in hopes that maybe someday I'll GET IT!
Thanks again.
Corinne Null
Bedford, NH
cnull@MCIONE.com
David Hendley on sat 10 jan 98
>So, this puts me into another frame of mind. Can I make a list ingredients
>that are "trouble, with a capital T" (and I don't mean for toxicity, I mean
_____________________________________________
Connie, you can't make a list like that.
(Well, you can if you want to, but it won't do you any good).
There are too many variables.
And differing opinions.
A couple of examples:
1) I use whiting in every glaze I mix.
Every one. 100%.
And here you have it on your 'Trouble with a Capital T' list.
When I first set up my shop I bought 100 lbs.
of wollanstonite and I haven't opened the bag.
I've never had any problems that I can trace back
to whiting, so why use the wollanstonite at 3 times the price?
But, I know for a fact that other people like to use
wollanstonite rather than whiting to avoid outgassing problems.
This is because, I'm sure, they have had problems with whiting
in their particular application.
2) I also like gerstley borate and use it a lot.
In fact, I can't tell that my supply has varied through the years.
Others on the Clayart list are very vocal about
their absolute dislike for the stuff, giving it the name
'ghastly borate'.
Again, a bad experience or two will change your opinion
of a glaze material.
3) I would never even consider using Cornwall Stone,
because it makes no sense to me to ship rock powder
across the ocean when we have plenty here already.
But again, I'm sure there are knowledgeable glaze
formulators and good potters who think Cornwall Stone is great
and if I lived in Cornwall I probably would, too .
Any material, I suspect, used improperly, such as in too great a
quanity will cause problems for you.
David Hendley
>So, this puts me into another frame of mind. Can I make a list ingredients
>that are "trouble, with a capital T" (and I don't mean for toxicity, I mean
>for flaws)? So far I've got:
> Whiting
> Magnesium Carbonate
> sometimes - neph sy - crazing
> Anything else?
>
>
>Can I make another list of "variable but useful" ingredients?
> Gerstley Borate
> Dolomite
> Cornwall Stone
>
>Somehow I thought the lists would be longer.
>
>And, I still can't figure on the Bone Ash. Natural English or Synthetic?
>
>Please correct my thinking again if I'm STILL out in left field! I keep
>peeling away at this glaze onion, in hopes that maybe someday I'll GET IT!
>
>Thanks again.
>
>Corinne Null
>Bedford, NH
David Hendley
Maydelle, Texas
See David Hendley's Pottery Page at
http://www.sosis.com/hendley/david/
shelford on sun 11 jan 98
Corinne -
Re: >Can I make a list ingredients
>that are "trouble, with a capital T" (and I don't mean for toxicity, I mean
>for flaws)? So far I've got:
> Whiting
> Magnesium Carbonate
> sometimes - neph sy - crazing
> Anything else?
Hang on, here. I don't think anyone meant you to write off those
ingredients. They can be troublesome in some circumstances, no doubt, but a
lot of great glazes use them without problems. The big thing in glazes is
not the individual ingredients, it's what they do in combination. Seems to
me, the time to worry about them is when you've tested, and had problems.
How you done much testing yourself? When you consider that it is very rare
for the same glaze to turn out the same for any two potters, it makes sense
to test all these things in your own studio, in your own kiln, if you want
to understand what they will do, or not do, for you. Have you got a good
text or two on glazes, so you know what you are looking for when you test?
This applies to your other list as well.
And the bone ash - well, try a glaze you know, with both kinds. I haven't
noticed a lot of difference between the only bit of natural bone ash I've
been able to test, and the synthetic, but that probably depends on the
sensitivity of the particular glaze too.
The info you get on this list can fantastically useful and educational, but
it doesn't let you off the testing part. The gods that oversee pottery are
an odd bunch - a lot of puritans, and a lot of clowns. You have to get in
good with both sides...
BTW, have you seen those nifty little field microscopes with a light built
in, that let you look at a glaze REAL closely? I'm not sure it tells you a
huge amount, but it sure shows up something of the structure of the glaze,
and minor crazing, and all the crystals and stuff. I consider it one of
those toys that brightens the otherwise unbelievably tedious business of
glaze testing.
- Veronica
___________________________________________
Veronica Shelford
e-mail: shelford@island.net
s-mail: P.O. Box 6-15
Thetis Island, BC V0R 2Y0
Tel: (250) 246-1509
Louis Katz on mon 12 jan 98
Things are seldom what they seem....
Whiting a.k.a. calcium carbonate is done outgassing by 2000 if it is
relatively pure. I have never seen a pinholing problem that I attributed to
this in cone ten glazes. Of course I may not have been looking.
In terms of safety, if it wasn't for the impurities you could consume a
considerable amout of calcium carbonate daily and call it a food
suppliment. Although I would not suggest not wearing a respirator when
using it, if pure it is probably one of the safer materials in our studios
to inhale.
All ingredients are trouble, and all are blessings; today I sound like a
Taoist.
The uses of Magnesium Carbonate are more limited, but when a small amount
of flocculation in a glaze is needed it can do wonders. Why live without
it?
When more magnesium is needed Dolomite does the trick unless you don't want
the Calcium along with it. Talc takes care of this unless you are already
long on silica.
In terms of bone ash I think you have it right, get Natural English or
Synthetic. Don't make it yourself, the process stinks. If you do get
synthetic Bone ash find out what it actually is, not what it tis supposed
to look like.
Some of the most interesting things are complicated.
If you are looking for a list of chemicals to buy, get some recipes that
you find interesting, figure out how much you need to mix at least 1000
grams of each and buy the materials you need for them. Then when you have
done a little testing by materials in larger quantities.
Louis Katz
Ron Roy on mon 12 jan 98
I too use whiting and have no trouble - but I fire at cone 10 - as does
David - at least cone 10. It may be a problem at lower temps however. Some
say the CO2 creates bubbles in clear glazes at cone 6 in boron glazes and a
replacement with wolastonite helps solve the problem - maybe - I'm not
convinced about that. I do know that trying to cut down on ignition loss
buy substituting dolomite would not work - the loss in ignition for Whiting
is around 45% - that's CO2 up the chimney - the loss for dolomite is about
the same.
I don't know how to figurer this out but - if you are paying 10 cents a
pound for whiting - and all that bought and paid for CO2 is lost what are
you really paying for whiting? Wolastonite has a loss of about 2.0.
I can say that I am sure that getting your MgO from Talc or Dolomite is the
cheaper way and you will avoid those nasty crawling problems - unless of
course you want them. The Loss for Magnesium carb is arounf 52%.
>1) I use whiting in every glaze I mix.
>Every one. 100%.
>And here you have it on your 'Trouble with a Capital T' list.
>When I first set up my shop I bought 100 lbs.
>of wollanstonite and I haven't opened the bag.
>I've never had any problems that I can trace back
>to whiting, so why use the wollanstonite at 3 times the price?
>But, I know for a fact that other people like to use
>wollanstonite rather than whiting to avoid outgassing problems.
>This is because, I'm sure, they have had problems with whiting
>in their particular application.
>David Hendley
Ron Roy
93 Pegasus Trail
Scarborough,Canada
M1G 3N8
Evenings, call 416 439 2621
Fax, 416 438 7849
Studio: 416-752-7862.
Email ronroy@astral.magic.ca
Home page http://digitalfire.com/education/people/ronroy.htm
DONPREY on mon 12 jan 98
Veronica,
Thanks for mentioning the field microscope. I have a bit of money to spend on
tools or toys, but I couldn't think what is was I needed/wanted. Now I
remember! It's a field microscope. I borrowed one from a friend years ago
and found it very useful (if only to satisfy curiosity). I'll bet my
granddaughter will also find it interesting. Thanks. (also liked you
comments on glaze/material testing)
Don Prey in Oregon
Leslie Norton on tue 13 jan 98
Corinne,
There is really nothing wrong with using Whiting, Magnesium Carbonate or
Neph Sy. It all comes down to combinations and what combination works for
you. There are lots of glazes made with these ingredients that work great.
If you get pinholing, or crazing or what ever you can probably correct it
with some adjustment to the glaze. If that "magic" color is only created by
the presense of a certain ingredient, adjust the glaze to make it work,
don't throw out the glaze. These "T" ingredients are part of the glaze
vocabulary because they do work. Like I use to tell my students many years
ago, if something doesn't appear to be working correctly, adjust and
experiment, you might find something new and very exciting.
-Leslie
> -----Original Message-----
> From: Corinne Null [SMTP:cnull@mcione.com]
> Sent: Friday, January 09, 1998 2:16 PM
> To: Multiple recipients of list CLAYART
> Subject: chemicals
>
> ----------------------------Original message----------------------------
> Many thanks for all the helpful responses on this thread. I've decided
> that it's OK to use Dolomite and Talc and Rutile, and that I might do well
> to stay away from Whiting and Magnesium Carbonate if I'm having pinholing
> problems because of outgassing at high temps. (Have I got that right?)
> Tom
> Buck was the walking encyclopedia on this one!
>
> David Hendley pointed out the aspect of the amount of processing being a
> large part of the expense of the purer ingredients. Louis Katz and Leslie
> Norton observed that the more intimately involved ingredients behave
> better.
>
> So, this puts me into another frame of mind. Can I make a list
> ingredients
> that are "trouble, with a capital T" (and I don't mean for toxicity, I
> mean
> for flaws)? So far I've got:
> Whiting
> Magnesium Carbonate
> sometimes - neph sy - crazing
> Anything else?
>
>
> Can I make another list of "variable but useful" ingredients?
> Gerstley Borate
> Dolomite
> Cornwall Stone
>
> Somehow I thought the lists would be longer.
>
> And, I still can't figure on the Bone Ash. Natural English or Synthetic?
>
> Please correct my thinking again if I'm STILL out in left field! I keep
> peeling away at this glaze onion, in hopes that maybe someday I'll GET
> IT!
>
> Thanks again.
>
> Corinne Null
> Bedford, NH
>
> cnull@MCIONE.com
Greg Skipper on thu 15 jan 98
Hi:
Somebody tonight showed me some clay art glazed with oxide wash. It's
what I've been looking for! Can you use any oxide and how do you mix it
(? just add water)? Does it matter what strength?
Thanks
Greg
M. Carroll on sat 29 may 04
Have been potting for quite a few years but realize there is a giant gap =
in my knowledge of raw glaze materials. Especially reading some of the =
posts where substitutions are recommended or experiments are being =
launched. Feel a little like the joke about the city person who thinks =
milk comes from the supermarket because they've never seen the cow. =
Have mixed glazes of course according to recipes but need to go beyond. =
Is there any book you can recommend or does one have to take a =
chemistry course. All my art courses have been hands on ceramics. Thank =
you. Reply to home email is okay. M. Carroll
daniel on sun 30 may 04
Hi M,
> Is there any book you can recommend or does one have to take a chemistry course. All
> my art courses have been hands on ceramics.
Most books on glazes have some material on materials and what oxides they
source, some benefits, side effects and so on. I have found that I have a
number of books with repeated info or bits not found elsewhere, but you
might try :
Mimi Obstler's, Out of the Earth, Into the Fire. I'm just starting this
one, but I really like the approach and the data from the tests is great. It
is sub-titled "A Course in Ceramic Materials for the Studio Potter".
I have only touched the surface and am only beginning tests but its got a
ton of info in it.
Thanx
D
Belmont, California, USA
(ex terra australis)
Carol Tripp on sun 30 may 04
Dear M.
The very first "book" on glaze chemistry I read was on the internet. Go to
http://grafik.sdsu.edu/ceramicsweb//
find "Class Materials and Education"
read "about Class Materials-Please read"
Then click "Class Materials and Technical Handouts" and then prepare to
spend time reading and reading and reading again. It will sink in.
Best regards,
Carol
Dubai, UAE
part of what M. Carroll wrote:
Is there any book you can recommend or does one have to take a chemistry
course. All my art courses have been hands on ceramics. Thank you.
_________________________________________________________________
Tired of spam? Get advanced junk mail protection with MSN 8.
http://join.msn.com/?page=features/junkmail
Ivor and Olive Lewis on sun 30 may 04
Dear M. Carroll,
When I started out there were almost no books to be found. Then round
about 1979 I came across one of the best ever published and bought a
copy. Look for Emmanuel Cooper and Dereck Royle, "Glazes for the
Studio Potter" 1978 ISBN 0-7134-3291-8.
The book is divided into three basic sections; "Making the Glaze",
'Understanding the Glaze", "Using the Glaze". Plus appendices.
Now it is not perfect but it is good. The only problem is that it may
be out of print and some materials may be obsolete or unobtainable
where you are.
My suggestion would be get your hands on a copy (remember the rules
for out of print books! ) Read it slowly and adsorb the information.
If you run into bother come back to Clayart with well thought out
questions.
Best regards,Ivor Lewis. Redhill, South Australia
Potters Council Member
Diane Rae on mon 31 may 04
>>>>>>part of what M. Carroll wrote:
Is there any book you can recommend or does one have to take a
chemistry course. All my art courses have been hands on ceramics.
Thank you.<<<<<<<<<
M:
I had just sent Ron Roy a direct e-mail regarding his book, "Mastering
Cone 6 Glazes" when I read your post. I will cut and paste my e-mail
to him as well as his reply. Perhaps this book can help you out like it
has me!
>Dear Ron Roy,
>I've been meaning to write you ever since I purchased your
"Mastering Cone 6
>Glazes" about six months ago. I typically read books starting at the
back
>and leafing toward the front. Amazed I was to find a book mark at the
back
>of your book! After a few days of leafing around....I found that your
book
>is the FIRST (non fiction) book I've ever wanted to read from cover to
back.
>So, I figured you understood the back to front reading style and
offered
>this bookmark as a challenge to the *dyslexic* readers out there.
>
>I've loaned it to another local potter, but am ready to get it back. One
>should never become too complacent with the "comfortable"
glazes....I'm
>ready to start experimenting again.
>
>Thank you so much for your contributions to my potter's world.
RON ROY'S REPLY:
Dear Diane,
Thanks for a wonderful post - John and I are thrilled to get this kind of
message. We tried hard to write a book that would be understood by
anyone
who was not skilled in chemistry.
I am forwarding this to John - please keep us informed about your
progress.
Best regards and thanks for writing - RR
Diane Rae
Royal Thrown Pottery
Great Falls Montana where the wind never stops and there are no falls
left, just dams.
Hank Murrow on mon 31 may 04
Dear M. Carroll;
I have found Ian Currie's book "Revealing Glazes" to be a very
effective tool in bringing folks new to glaze formulation along
quickly. It may be ordered from Ian directly at:
http://www.ian.currie.to/index.html where you will also find a
description of the method and the book itself.
Cheers, Hank on the workshop trail in CT.
On May 29, 2004, at 6:19 PM, M. Carroll wrote:
> Have been potting for quite a few years but realize there is a giant
> gap in my knowledge of raw glaze materials. Especially reading some
> of the posts where substitutions are recommended or experiments are
> being launched. Feel a little like the joke about the city person who
> thinks milk comes from the supermarket because they've never seen the
> cow. Have mixed glazes of course according to recipes but need to go
> beyond. Is there any book you can recommend or does one have to take
> a chemistry course. All my art courses have been hands on ceramics.
> Thank you. Reply to home email is okay. M. Carroll
M. Carroll on mon 31 may 04
Have had wonderful feedback on books, websites, courses, articles on =
learning more
about the above. Interesting that the same titles kept coming up. Am =
becoming
Amazon's favorite customer. Thank you John, Paul, Daniel, Carol, Diane =
et al.
M. Carroll
Cynthia Bracker on tue 1 jun 04
I've been gone for the last few days and slowly getting through posts.
I have been watching this thread to see if someone mentions Ian's book.
I agree it is excellent. Besides purchasing from Ian directly (he is in
Australia) the book can be purchased from just about any major ceramic
supplier.
Cindy
Hank Murrow wrote:
> Dear M. Carroll;
>
> I have found Ian Currie's book "Revealing Glazes" to be a very
> effective tool in bringing folks new to glaze formulation along
> quickly. It may be ordered from Ian directly at:
> http://www.ian.currie.to/index.html where you will also find a
> description of the method and the book itself.
>
> Cheers, Hank on the workshop trail in CT.
>
> On May 29, 2004, at 6:19 PM, M. Carroll wrote:
>
>> Have been potting for quite a few years but realize there is a giant
>> gap in my knowledge of raw glaze materials. Especially reading some
>> of the posts where substitutions are recommended or experiments are
>> being launched. Feel a little like the joke about the city person who
>> thinks milk comes from the supermarket because they've never seen the
>> cow. Have mixed glazes of course according to recipes but need to go
>> beyond. Is there any book you can recommend or does one have to take
>> a chemistry course. All my art courses have been hands on ceramics.
>> Thank you. Reply to home email is okay. M. Carroll
>
>
> ______________________________________________________________________________
>
> 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.
>
>
Linda M on wed 8 dec 04
I've been looking over my glaze recipes and I have two questions. Can
Feldspar F4 Soda be used in place of Kona F4 Feldspar and Custer Feldspar
in a recipe? Second question: Can Kentucky Ball Clay be used in place of
Tennessee Ball Clay in a recipe? Thank you for your answers in advance.
Linda Marcoux
David Hewitt on thu 9 dec 04
Linda,
As the name indicates, Feldspar F4 Soda is relatively high in Na2O
compared to potash feldspars such as Custer Feldspar were the K2O is
relatively higher. There are also other differences in respect of the
Al2O3 and SiO2 amounts. You would, therefore, find some difference if
you were to sub these two materials.
From what I can find on Kentucky and Tennessee Ball clays, they seem to
be very similar. May be others can confirm this or otherwise.
David
In message , Linda M writes
>I've been looking over my glaze recipes and I have two questions. Can
>Feldspar F4 Soda be used in place of Kona F4 Feldspar and Custer Feldspar
>in a recipe? Second question: Can Kentucky Ball Clay be used in place of
>Tennessee Ball Clay in a recipe? Thank you for your answers in advance.
>Linda Marcoux
--
David Hewitt
Web:- http://www.dhpot.demon.co.uk
william schran on thu 9 dec 04
Linda wrote:>Can Feldspar F4 Soda be used in place of Kona F4
Feldspar and Custer Feldspar
in a recipe? Second question: Can Kentucky Ball Clay be used in place of
Tennessee Ball Clay in a recipe?<
I generally substitute one soda feldspar for another 1 to 1, Minspar
for Kona F4 and have not seen a difference in the results. These are
soda feldspars. Custer is a potash feldspar, so you can't substitute
Custer for F4. You could substitute G200 feldspar for the Custer.
I use Kentucky OM4 ball clay for all glazes containing ball clay.
Subbing OM4 for Tennessee would probably be ok, but not having used
the Tennessee ball clay, I couldn't advise on the results.
Bill
Cynthia Bracker on thu 9 dec 04
I think that your reference to Feldspar F4 is the same as Kona F4. The
other main soda spar is NC-4. Custer and G-200 are potash feldspars.
G-200 is usually only used in glaze recipes, not clay bodies. Generally
you can sub one soda spar for another and one potash spar for another,
but subbing potash for soda or vice-versa will change the recipe quite a
bit.
Kentucky Ball Clay and Tennessee Ball clay are probably fine to be used
interchangeably. Remember, state lines were drawn by human beings.
What's in the ground doesn't know if it is in the state of TN or KY.
However, some mines have different percentages of impurities. For
example, OM-4 stands for Old Mine Number 4. It is located in Kentucky,
but the vein runs through Tennessee. SGP#1 is from a Tennessee Mine
"number 1" it has less iron and other impurities in it than OM-4.
KT1-4 stands for Kentucky-Tennessee Mines #1 & #4. It is essentially a
scoop of OM4 and a scoop of SGP. I think I'm just rambling at this
point though, so I'll stop. I hope I've at least answered your questions!
Cindy Bracker
Bracker's Good Earth Clays, Inc.
Linda M wrote:
>I've been looking over my glaze recipes and I have two questions. Can
>Feldspar F4 Soda be used in place of Kona F4 Feldspar and Custer Feldspar
>in a recipe? Second question: Can Kentucky Ball Clay be used in place of
>Tennessee Ball Clay in a recipe? Thank you for your answers in advance.
>Linda Marcoux
>
>______________________________________________________________________________
>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 fri 10 dec 04
Hi Linda,
You have the answer for the F4 spar - same stuff.
There are many Tennessee and Kentucky ball clays - if you tell me which
ones you have I can tell you which will be OK to sub one for the other -
some are quite different and if that is the case the recipe should be
adjusted - I can do that easy.
RR
>I've been looking over my glaze recipes and I have two questions. Can
>Feldspar F4 Soda be used in place of Kona F4 Feldspar and Custer Feldspar
>in a recipe? Second question: Can Kentucky Ball Clay be used in place of
>Tennessee Ball Clay in a recipe? Thank you for your answers in advance.
>Linda Marcoux
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Edouard Bastarache Inc. on fri 10 dec 04
Hello all,
J.Chappell in his book says that in the case of glazes
ball clays are interchangeable; but they are not in the
case of clays.
Later,
"Ils sont fous ces quebecois"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
Ron Roy on sat 11 dec 04
Not so - it depends on how much clay is in the recipe and how much the
glaze depends on the alumina/silica ratio.
RR
>J.Chappell in his book says that in the case of glazes
>ball clays are interchangeable; but they are not in the
>case of clays.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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