Fredrick Paget on mon 12 mar 07
>Hi Clayarters,
>I inherited a box of glaze chemicals that are about 20 years old and need
>help since I this is my first attempt at making my own glaze. Any help
>with any of these questions will be much appreciated.
>
>1. Cornwall Stone- What do I use it for? I have not seen a single recipe
>that calls for this. Can this be a substitute for any other ingredient?
>2. Never seen the following either. What can I do with these?
>Magnesium Carbonate:
>Potassium Dichromate:
>Jordan clay:
>
>3. Custer and G200 are both potash feldspars, so can I exchange them in
>recipes, and Kona feldspar is a soda feldspar so this is different than
>potash feldspars?
>4. Some recipes call for Bone ash. I have volcanic ash, soda ash, pumice,
>wood ash, but no Bone ash. Can I use these other ashes as a sub?
>5. Yellow Ochre: I have heard that this can be substituted for RIO in ^6
>oxidation? Is this true?
>6. I assume whiting is the same as English Whiting, yes?
>
>Thank you in advance! Vaishali.
I just heard that Cornwall stone was mined out . That is the mine
is empty. Hang on to it, It is valuable. It is a sort of feldspar
with clay minerals in it. It is used in some glazes and porcelain
clay bodies.
Magnesium carbonate is not used much but is a glaze ingredient.
Potassium Dichromate is water soluble and a carcinogen. It is
dangerously poison. Not currently used in ceramics although in the
past it was used with tin to make a pink color. Now days you can buy
this color in a Mason stain that is insoluble and much safer. Also
used in photography in the gum bichromate process so it has some
value to practitioners of ancient alternative photographic
techniques. Ammonium bichromate is preferable there however.
Jordan clay sounds like it may be a slip clay used in glazes but I
am not sure.
I believe you are ok substituting G200 for Custer in most cases.
Sticklers will want to use glaze calculation software to fine tune
the formula. You are right on Kona it is different and that makes a
difference in some cases.
Bone ash has a lot of Phosphorus in it and none of those others do
Soda ash is not ash at all but is an impure sodium carbonate.
Volcanic ash and pumice are almost the same thing. The formula
varies from source to source.
Wood ash is mostly calcium hydroxide and other stuff depending on
the kind of wood. Used in true ash glazes, A subject in its self.
Whiting is calcium carbonate, Same as marble, limestone and sea
shells. Don't know about English Whiting.
This is all off the top of my head so 100 percent accuracy not
guaranteed. If you want that hold on until the gurus come back from
NCECA ( which I had to skip this year).
Also there is a book "Potter's Dictionary"by Hammer and Hammer that
will have the true story on most of these chemicals.
Fred
--
Twin Dragon Studio
Mill Valley, CA, USA
Vaishali Wagh on tue 13 mar 07
Hi Clayarters,
I inherited a box of glaze chemicals that are about 20 years old and need
help since I this is my first attempt at making my own glaze. Any help
with any of these questions will be much appreciated.
1. Cornwall Stone- What do I use it for? I have not seen a single recipe
that calls for this. Can this be a substitute for any other ingredient?
2. Never seen the following either. What can I do with these?
Magnesium Carbonate:
Potassium Dichromate:
Jordan clay:
3. Custer and G200 are both potash feldspars, so can I exchange them in
recipes, and Kona feldspar is a soda feldspar so this is different than
potash feldspars?
4. Some recipes call for Bone ash. I have volcanic ash, soda ash, pumice,
wood ash, but no Bone ash. Can I use these other ashes as a sub?
5. Yellow Ochre: I have heard that this can be substituted for RIO in ^6
oxidation? Is this true?
6. I assume whiting is the same as English Whiting, yes?
Thank you in advance! Vaishali.
Chris Trabka on tue 13 mar 07
Vaishali,
There are two books that can help you understand glazes and glaze
chemicals:
The Complete Guide to High-Fire Glazes: by John Britt.
Mastering Cone 6 Glazes: by John Hesselberth & Ron Roy.
The books will guide you to many other books on glazes and glaze chemicals.
Chris
>Hi Clayarters,
>I inherited a box of glaze chemicals that are about 20 years old and need
>help since I this is my first attempt at making my own glaze. Any help
>with any of these questions will be much appreciated.
>
>1. Cornwall Stone- What do I use it for? I have not seen a single recipe
>that calls for this. Can this be a substitute for any other ingredient?
>2. Never seen the following either. What can I do with these?
>Magnesium Carbonate:
>Potassium Dichromate:
>Jordan clay:
>
>3. Custer and G200 are both potash feldspars, so can I exchange them in
>recipes, and Kona feldspar is a soda feldspar so this is different than
>potash feldspars?
>4. Some recipes call for Bone ash. I have volcanic ash, soda ash, pumice,
>wood ash, but no Bone ash. Can I use these other ashes as a sub?
>5. Yellow Ochre: I have heard that this can be substituted for RIO in ^6
>oxidation? Is this true?
>6. I assume whiting is the same as English Whiting, yes?
>
>Thank you in advance! Vaishali.
>
>___________________________________________________________________________
___
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
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>
>Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
Edouard Bastarache Inc. on tue 13 mar 07
Jordan Clay :
This a high quality stoneware clay which is used
in clay bodies to produce cream to buff colored
bodies. (James Chappell, 1977)
Later,
Edouard Bastarache
Le Français Volant
The Flying Frenchman
Sorel-Tracy
Quebec
http://www.sorel-tracy.qc.ca/~edouardb/Welcome.html
http://perso.orange.fr/smart2000/livres.htm
http://www.pshcanada.com/Toxicology.htm
www.thepottersshop.blogspot.com
http://www.ceramique.com/cerambooks/rayons/technologie.php
http://www.flickr.com/photos/30058682@N00/
The Goodsons on tue 13 mar 07
Dear Vaishali,
Good evening! I am slowly reading the book, "Out of the Earth, and
into the Fire" by Mimi Obstler. Tonight I came across several of the
chemicals that you mentioned. This book tells about Cornwall Stone
and Jordan clay. The book tells that Jordan clay is no longer
available and that makes me think it might be valuable like the Cornwall
stone. On page 93 it reads "Jordan clay, a ball clay from Poplar,
Maryland ... Jordan was a plastic, fine grained ball clay with a high
silica content (68%)" There is a paragraph discussing the substitution
of gold art clay for Jordan clay. It also compares it to Foundry Hill
Creme and Kentucky Stone. The book tell that the Jordan clay produces
"beautiful, warm, red-orange smooth surface". It sounds really nice!
Good luck with all your chemicals,
Linda Goodson
Lincolnton, NC
> ______________________________________________________________________________
>
> 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.
>
claystevslat on wed 14 mar 07
Vaishali --
Potassium Dichromate is nasty stuff -- corrosive, poisonous,
carcinogenic, can be absorbed through the skin or through
inhalation -- find a recycler who'll take it off your hands.
Cornwall stone is used in many recipes, it's like a cousin to
our regular feldspars -- some Cornwall stone is a little purple and
has a bit of flourine in them; the ones that are whiter lack
the flourine and may have less potassium and sodium.
Magnesium Carbonate is very refractory -- if you want magnesium in a
glaze, it's probably easier to formulate a recipe with talc or
dolomite in it.
Kona does not substitute well for Custer or G-200 -- it's called a
soda feldspar because it has lots more sodium than the ones called
potash feldspar which have less sodium and more potassium. Sodium
gives better colors sometimes, but creates more fit problems at
cone 6 (seems to be less of a problem at 10.)
Bone ash is a unique material because it's rich in phosphorous.
The other ashes are not.
I hope some of this helps. When you're starting out, it's probably
best not to begin with substitutions -- find a recipe that you can
use with the materials you have or can acquire.
There are hundreds of recipes in the archives; something should hit -
- about 95% of all glazes call for silica, clay (ball clay or
kaolin) and feldspar or a frit. It doesn't take too many materials
to make a few good glazes and get started.
-- Steve Slatin
--- In clayart@yahoogroups.com, Vaishali Wagh
wrote:
>
> Hi Clayarters,
> I inherited a box of glaze chemicals that are about 20 years old
and need
> help since I this is my first attempt at making my own glaze.
Eleanora Eden on thu 15 mar 07
Hi Vaishali,
Bone ash used to be made from calcined bones. Now it is available
in a chemical approximation. I have bone ash also from an earlier era and
Ron Roy told me that it is not what is available now.
Here is an earlier post on the subject:
>Does anyone have a source for real calcined bone ash? Not the synthetic
>Tri-Calcium Phosphate.
Eleanora
>Hi Clayarters,
>I inherited a box of glaze chemicals that are about 20 years old and need
>help since I this is my first attempt at making my own glaze. Any help
>with any of these questions will be much appreciated.
>
>1. Cornwall Stone- What do I use it for? I have not seen a single recipe
>that calls for this. Can this be a substitute for any other ingredient?
>2. Never seen the following either. What can I do with these?
>Magnesium Carbonate:
>Potassium Dichromate:
>Jordan clay:
>
>3. Custer and G200 are both potash feldspars, so can I exchange them in
>recipes, and Kona feldspar is a soda feldspar so this is different than
>potash feldspars?
>4. Some recipes call for Bone ash. I have volcanic ash, soda ash, pumice,
>wood ash, but no Bone ash. Can I use these other ashes as a sub?
>5. Yellow Ochre: I have heard that this can be substituted for RIO in ^6
>oxidation? Is this true?
>6. I assume whiting is the same as English Whiting, yes?
>
>Thank you in advance! Vaishali.
>
>______________________________________________________________________________
>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.
--
Bellows Falls Vermont
www.eleanoraeden.com
Peter H. Pache on sun 18 mar 07
>>Does anyone have a source for real calcined bone ash? Not the synthetic
>>Tri-Calcium Phosphate.>>
It is still available in the US from:
http://ebonex.com/
I ordered a couple of bags last year --
Best--
Peter
NM
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John Hesselberth on mon 19 mar 07
If you are have a pet crematorium nearby, give them a call.
Regards,
John
>>> Does anyone have a source for real calcined bone ash? Not the
>>> synthetic
>>> Tri-Calcium Phosphate.>>
>
Thomas Malone on mon 19 mar 07
Hello,
Problem is that synthetic is different to traditional bone ash. For the
real stuff have a look at www.potterycrafts.co.uk (I think are the biggest
supplier to studio potters in the UK)
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