Milton Markey on mon 12 mar 01
In a message dated 3/12/2001,Martin writes:
> So dear Clayarters, ALWAYS list the formulae of glazes, NOT the Recipes,
> which are, frankly, useless unless you live virtually next door to the
> poster of that glaze and get your RMs from the same shop at the same time.
>
Hi Martin!
I'm not certain what you're requesting. There seems to be a lot of different
ways of expressing the contents of a glaze. Most of us are familiar with the
percentage format(ie, 10% whiting, 40% borax, etc), and then there is the
format that gives one the matrix that's calculated (usually done with a
computer glaze calculation program), and several other forms of contents
expression.
Could you post an example of exactly what you'd like to see posted, as a
reply to a glaze request? I'll gladly honor your request in the future, once
I get an idea of what is requested. Perhaps providing the percentage format,
followed by your suggested format will be helpful to compare the two. I'm
certain you have a glaze "formulae" that you're willing to provide as an
example.
Thanks for giving us a "heads up" with your concern.
Milton NakedClay@AOL.COM
Yucca Valley, CA
Getting warmer, and the sky is clear. Desert flowers are sure to appear in a
few weeks. I'll be issuing "fragrant flower miles" to visitors!
Martin Howard on mon 12 mar 01
Thank you David Hendley for posting:-
current analysis. Every boxcar load of material has an analysis
specifically for that batch.>
The batches in each county, each country differ, depending on where it came
from, which seam, which part of a seam, what the miners and factories did
with it etc etc.
The analysis is most important, essential to us all. Some stupid suppliers
of RMs don't understand this and still hide the analysis away from
purchasers as if it should be secret.
Therefore it is important to stop assuming that Whiting is Whiting full
stop. Frits with a definite number and name from the same supplier may well
be the same, but even those companies are now seeing the light and letting
go of the analysis. But it's been a hard won fight.
So dear Clayarters, ALWAYS list the formulae of glazes, NOT the Recipes,
which are, frankly, useless unless you live virtually next door to the
poster of that glaze and get your RMs from the same shop at the same time.
Martin Howard
Webb's Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
England
martin@webbscottage.co.uk
www.webbscottage.co.uk now available to all. Have fun! I list some recipes
there, but will change them all to formulae on request:-)
vince pitelka on tue 13 mar 01
Martin -
I'm sorry, but your request that glazes be presented as formulae rather than
as recipes is not practical or reasonable. Providing the formula will not
allow the individual potter to reproduce the same glaze at all, because the
formula does not include trace materials which are critical to the glaze.
As you know, many glaze materials contain extensive amounts of trace
materials which do not appear at all in the unity formula. The recipe is
absolutely critical in order to reproduce the same glaze, if that is the
intention. If you live elsewhere in the world, and have to use other
materials, then you must adapt the recipe to your materials. And in most
cases, many people who post recipes will be happy to send you the glaze
formula off-list. When possible, it is great if people can post both the
recipe and the formula, but to ask for the formula only does not seem
appropriate.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
http://www.craftcenter.tntech.edu/
Cindy Strnad on tue 13 mar 01
Posting formulae would be nice, of course.
But to be honest, if I have to go and dig out all my materials sheets and
alter my data tables and the whole nine yards before I can share a glaze, I
probably won't post any glazes at all. I do appreciate the glazes others
have posted here, with or without formulae. If they don't work for me, I may
play with them a bit and make them work, or not. Doing the whole formula
thing just isn't going to work for me.
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
earthenv@gwtc.net
http://www.earthenvesselssd.com
Louis Katz on tue 13 mar 01
Unfortunately neither method is the be all and end all. Just try to substitute for
say Gertsley Borate. Even with the analysis you can't get the glazes to look the
same. Albany substitutes, the soluble soda ash in a shino recipe, all of these
when presented as molecular formula leave something to be desired. My suggestion
would be to list them both ways if possible. If not, do what you can do.
Martin Howard on tue 13 mar 01
Milton asks for an example of what I mean. So here goes:-
RM RECIPE AMOUNT
Standard White Earthenware 21.03
Flint / Quartz 21.19
FR002 Std. Borax 30.2
High AlkalineFR005 7.61
Standard Red Clay 3.86
Cat Litter 7.55
Iron Oxide (Red) 1.9
Granite Dust 15.1
Pet Ash 10.46
Total 118.9
Now for the Formula of the same glaze
SEGER % WT.
K2O 0.074 2.927
Na2O 0.159 4.150
CaO 0.728 17.195
MgO 0.038 0.638
ZnO 0.002 0.073
1.000 24.98
Al2O3 0.191 8.204
B2O3 0.186 5.499
Fe2O3 0.043 2.917
0.420 16.62
SiO2 2.196 55.603
TiO2 0.005 0.156
P2O5 0.043 2.593
ZrO2 0.001 0.042
2.245 58.39
Rather erratic columns, but it should show the difference.
Martin Howard
Webb's Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
England
martin@webbscottage.co.uk
www.webbscottage.co.uk
David Hewitt on tue 13 mar 01
I couldn't agree more with these views about the variability of supplies
from different sources and the need for an analysis to go with a recipe.
The analysis, of course needs to based on what was actually in the
recipe, not a generic analysis or one not up-to-date. There is virtue in
seeing the recipe if only to know the original type of material used to
source each oxide in the analysis.
'Transporting' recipes across the world has many pitfalls, but this type
of information and a glaze calculation program are the tools for getting
the best results.
In message , Martin Howard writes
>Thank you David Hendley for posting:-
>>current analysis. Every boxcar load of material has an analysis
>specifically for that batch.>
>
>So dear Clayarters, ALWAYS list the formulae of glazes, NOT the Recipes,
>which are, frankly, useless unless you live virtually next door to the
>poster of that glaze and get your RMs from the same shop at the same time=
>=2E
>
>Martin Howard
>Webb's Cottage Pottery
>Woolpits Road, Great Saling
>BRAINTREE, Essex CM7 5DZ
>England
>
--
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
Wade Blocker on tue 13 mar 01
I agree Cindy. If formulas were posted rather than recipes, I would not be
able to use them. Mia in springlike ABQ
Tom Buck on wed 14 mar 01
Cindy (and Martin H):
While we all should strive to provide both the Batch Recipe and
the Seger Formula, it is often difficult for potters who have yet to
undertake, as I do, glaze calculations as a matter of routine.
As has been noted here (eg, mel just last week), glazes do not
travel well. Ones posted in a book or on Clayart rely on the alert potter
to match both claybody and the glaze raw materials. When continents
separate us, and indeed when 1000 km separate us, it is difficult for that
matching to occur.
I urge Cindy to seek a method of doing glaze calcuation when it
seems appropriate, and thereby add the Seger Forumla to a recipe she posts
on Clayart.
But others, including Martin, should not expect everything to be
handed on a platter. You have to do some digging. There are some websites
(eg, Matrix in New Zealand) that are generous enough to provide a very
lengthy list of raw materials and their analyses. So, if you have a
glzcalc program you can determine the Seger Formula yourself, and then
work backwards using your own raw materials.
Tied into this is some superb glaze calculation programs
now available at prices equivalent to the selling price of a mid-sized
teapot.
My view after 10 years of doing glzcalc is that this skill is just
another of the many skills that the modern studio potter has to learn.
bye for now. peace. Tom B.
Tom Buck ) tel: 905-389-2339
(westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street,
Hamilton ON L8T 3E1 Canada
Martin Howard on wed 14 mar 01
Cindy's position is appreciated. I am not trying to be difficult or make
anyone change.
I just want us to be clear about this. Recipes only travel IF both sides to
the discussion have the same RMs with the same formulae.
Those with other RMS would probably love to convert the Recipes into
formulae and back to recipes using their own RMs. They cannot because they
do not have the analyses of your RMs.
Some of you use very pure RMs which, throughout probably the USA you can
rely on. So those recipes travel better in that area. Outside, they don't.
I use odd things, like cat litter, willow ash, granite dust, pet ash, ricoh
developer, etc so I am out of the otherwise wonderful discussions about
glazes, even if they were at my cones 1-3.
I wonder if the wizards of our computer glaze programs could tackle this
question and make it easier for us to pass on the formulae rather than the
recipes.
Martin Howard
Webb's Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
England
martin@webbscottage.co.uk
http://www.webbscottage.co.uk
Martin Howard on wed 14 mar 01
Vince you are certainly right, speaking in the USA for Americans.
But my point is that the glaze discussed in the list are 99% of no interest
to me, BECAUSE
1 I cannot get even close to copying the result without a formula of the
glaze or
2 obtain those raw materials mentioned in the recipe, or
3 if I did get those RMs it is most likely that they would not be from
the same mine, country or batch.
Yes, the very minor quantities of minor elements can make all the difference
to a glaze, but a full formula (and that depends on the method of analysis
in the lab) at least allows us foreigners to get somewhere close to the
glaze being discussed.
But as I mentioned before, this is rather academic to me, because so few
others on the list fire at my cones (1-2). I was only trying to help expand
the reason why glazes do not travel well.
I hope others do not try the glazes I show in my web site without testing
first:-)
I was only showing there a methodology that could so easily be added onto
David Hewitt's Glaze Book, to help day to day mixing records in the pottery.
This whole discussion is also academic to those without a computer or a
glaze program. Accepted. The maths are lengthy and tedious.
Martin Howard
Webb's Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
England
martin@webbscottage.co.uk
http://www.webbscottage.co.uk
Lawrence Ewing on wed 14 mar 01
And here's Martin's rather exotic recipe reconstructed in Matrix using
materials we have available here in Dunedin, New Zealand. Of course if
Martins glaze is a real one which we were trying to reproduce we would come
up against all sorts of variables resulting from the physical differences
between his amazing list of materials and the ones we have used to get a
near chemical match. But at least with the unity formula as a starting
point we get a lot closer initially than we otherwise would. Then of course
I do not really know what the original fired glaze looked like so I have no
physical target to go for..... the variables are many!!!
Kind regards,
Lawrence Ewing
email: lewing@clear.net.nz
phone +64 03 472 8801
MATRIX GLAZE CALCULATION SOFTWARE:
http://www.Matrix2000.co.nz
GLAZETEACH:
http://www.Matrix2000.co.nz/GlazeTeach
RM RECIPE Cone ? (possibly in the O4 range)
----------------------------------------------------------
Formula Weight% Recipe
----------------------------------------------------------
KNO 0.2328 7.16% Ferro 3134 23.65
CaO 0.7272 17.79% Bone Ash 5.85
MgO 0.0380 0.67% Neph. Sye. P3332 26.27
ZnO 0.0020 0.07% Pittong Eckalite 4.04
Al2O3 0.1915 8.51% Dolomite 3.57
P2O5 0.0430 2.66% Wollastonite 17.11
B2O3 0.1858 5.64% Zinc Oxide 0.07
SiO2 2.1917 57.45% Silica 19.46
TiO2 0.0008 0.04%
K2O 0.0616 2.53%
Na2O 0.1711 4.63%
Al:Si 11.4421
Expan.10.9501
ST 287.398
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]On
Behalf Of Martin Howard
Sent: Wednesday, March 14, 2001 8:20 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: FORMULAE not RECIPES
Milton asks for an example of what I mean. So here goes:-
RM RECIPE AMOUNT
Standard White Earthenware 21.03
Flint / Quartz 21.19
FR002 Std. Borax 30.2
High AlkalineFR005 7.61
Standard Red Clay 3.86
Cat Litter 7.55
Iron Oxide (Red) 1.9
Granite Dust 15.1
Pet Ash 10.46
Total 118.9
Now for the Formula of the same glaze
SEGER % WT.
K2O 0.074 2.927
Na2O 0.159 4.150
CaO 0.728 17.195
MgO 0.038 0.638
ZnO 0.002 0.073
1.000 24.98
Al2O3 0.191 8.204
B2O3 0.186 5.499
Fe2O3 0.043 2.917
0.420 16.62
SiO2 2.196 55.603
TiO2 0.005 0.156
P2O5 0.043 2.593
ZrO2 0.001 0.042
2.245 58.39
Rather erratic columns, but it should show the difference.
Martin Howard
Webb's Cottage Pottery
Woolpits Road, Great Saling
BRAINTREE, Essex CM7 5DZ
England
martin@webbscottage.co.uk
www.webbscottage.co.uk
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Logan Oplinger on wed 21 mar 01
Please don't hit (delete) me!! &:^)
Actually, I think three (four?) types of data are needed here;
1. Analysis (source?) of material,
2. Formulae, &
3. Recipes.
Thus has been the need for glaze calculation programs in order to accomodate the travelling glaze.
Then there are the innumerable clays and firing regimens which alter glazes in subtle and profound ways.
Testing cannot be eliminated, but organized informtion can provide clues if not direct answers to keeping the mental & physical drudgery/stress to a minimum.
Logan Oplinger
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