David Hendley on thu 30 dec 99
By trail and error, I have worked out cone formulations
that work for ME (read this as a big disclaimer; be sure
to rigorously test your homemade cones for accuracy
before you depend on them).
I made my mold for the cones by using Orton cones
to make a plaster gang mold for 6 cones. Do this by
laying the cones on a smooth flat surface, surrounding
them with a 1 X 4 'fence' and pouring in a few inches
of plaster.
My cones were sacrificed in the process. Perhaps you
could bisque-fire the cones first so they could be
used after being cast around.
Interestingly, in "The Potter's Alternative", by Harry
Davis, he says NOT to make a pyrometric cone mold
this way. He suggests sheet metal molds.
To make my cones, I mix up a recipe to plastic-clay
consistency, slightly over-fill each space in the mold,
and then tamp down and remove the excess with a
putty knife. It's important that you don't remove too
much material; an undersized cone will bend at a lower
work-heat point.
Since the recipes don't have much clay in them, they
mixtures are pretty short, but still fine to work with.
I used ball clay, with it's inherent impurities, to
improve the workability, so this throws my formulas
a little off from the theoretical cone formulas.
A 100 gram batch makes LOTS of cones.
CONE 10
Custer feldspar 17
Whiting 7
OM#4 ball clay 37
flint 31
(this adds up to 92)
CaO .67
MgO .03
K2O .21
Na2O .08
Fe2O3 .02
TiO2 .08
Al2O3 1.26
SiO2 10.02
CONE 8 1/2
I like this cone because it gives me a little earlier
warning than cone 9 for my cone 10 firings.
Custer feldspar 22.5
whiting 9
OM#4 ball clay 29
flint 39.5
(100 total)
CaO .69
MgO .02
K2O .21
Na2O .08
Fe2O3 .02
TiO2 .05
Al2O3 .90
SiO 8.96
--
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com/
John Britt on sun 2 jan 00
David Green wrote the best book I have ever read on cones and it is a
must read for those interested in Glaze chemistry! "Handbook of Pottery
Glazes" ISBN: 0-8230-2181-5 I believe it is out of print although it
is available through inter-library loan. (precursor to the internet) He
has devoted the first 60 pages to cones. Although the first 38 pages
are the most outstanding. He discusses Seger's paper in 1886 and the
theory that he used. It is a must read!
The discussion of the thinking process itself makes it important. He
began by choosing materials that were in use in the
porcelain industry on a large scale. (i.e. feldspar, whiting, silica
and kaolin.) He tried to use the purest ingredients , Zettlitz Kaolin,
Norwegian quartz, etc.. You can read it for yourself.
The making of cones is not really a concern for me. It is the knowledge
gained in the process that is important. Orton and other cone
manufacturers provide a product of amazing consistency, accuracy and
at a price that is unbeatable. The time you would spend thinking about
making cones
would far exceed the price they charge and that is not even counting,
making the molds, making the cones or the material cost, etc.
The first cone Seger made was cone 4 and he called
it "4" because of the amount of Silica. K20 -0.3, Ca0-0.7 Al203-0.5
and
silica 4.0. From cone 5 upwards the ratio of silica to alumina was
fixed at 1:10 , i.e. Al203-0.5 Si20-5.0 for cone 5 or Al203-0.6 Si02
-6.0 for cone 6 etc. (The flux column remains the same 0.3 K20 and 0.7
Ca0)
The illustrative part is the Silica/Alumina ratio. And when you
understand this, Ian Currie's "Stoneware Glazes" is much more
readable.
So using Insight, I formulated several cone recipes directly from
Seger's
theory, only using current materials. (Green gives recipes that Seger
used but since the materials are unavailable they are not very
accurate.)
For example Cone 9
Custer Feldspar-23.06g
EPK - 20.45g
Whiting - 9.66g
Silica (200m)- 46.82g
The Al/Si ratio is 0.9/9.0
Or cone 8:
Custer Feldspar-22.21g
EPK - 16.65g
Whiting - 9.30g
Silica (200m)-38.84g
The Al/Si ratio is 0.8/8.0.
These are fairly accurate although I have not tested them expensively.
If you want more recipes just let me know, although after reading
Green's book I am sure you will be able to formulate them yourself.
The remainder of Green's book is great too. He has great charts and
graphs on Rock materials, ash etc.
--
Thanks,
John Britt claydude@unicomp.net
Dys-Functional Pottery
Dallas, Texas
http://www.dysfunctionalpottery.com/claydude
http://www.silverhawk.com/ex99/britt/welcome.html
David Hendley on sun 2 jan 00
| David,
| Interresting. Just out of curiosity, do you dye them to tell them apart
at
| a glance?
| Have you also worked out any other recipes?
| Steve Dalton
I have never added dye to the cone recipes, although I
have thought about it, and think it is a good idea.
I tell them apart by making only one recipe a day,
and putting all the cones from each batch in a separate
labeled and dated box.
A few years ago, I worked on a recipe for cone 06, for
my bisque firings, but it needs some more refining, and
I haven't worked on it in a while.
This recipe works OK for a bisque firing, but I wouldn't
want to depend on it for a critical glaze firing.
These cones bend at the same time as a commercial
cone 06, but it happens a lot faster. When the commercial
cone is at 3 o'clock, this will still be straight up, then
10 minutes later, when the commercial cone is at 5 o'clock,
this one will be totally flat. Requires close monitoring!
Another drawback is that the recipe uses Gerstley borate,
which can, as we know, be variable. Next time, I would
use a frit instead.
CONE 06
Redart clay 48.5
Custer feldspar 9.0
Gerstley borate 28.0
whititng 10.5
CaO .65
MgO .07
K2O .11
Na2O .17
Fe2O3 .08
TiO2 .02
B2O3 .72
Al2O3 .31
SiO2 2.22
--
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com/
| >
| >----------------------------Original message----------------------------
| >By trail and error, I have worked out cone formulations
| >that work for ME (read this as a big disclaimer; be sure
| >to rigorously test your homemade cones for accuracy
| >before you depend on them).
| >
| >I made my mold for the cones by using Orton cones
| >to make a plaster gang mold for 6 cones. Do this by
| >laying the cones on a smooth flat surface, surrounding
| >them with a 1 X 4 'fence' and pouring in a few inches
| >of plaster.
| >My cones were sacrificed in the process. Perhaps you
| >could bisque-fire the cones first so they could be
| >used after being cast around.
| >Interestingly, in "The Potter's Alternative", by Harry
| >Davis, he says NOT to make a pyrometric cone mold
| >this way. He suggests sheet metal molds.
| >
| >To make my cones, I mix up a recipe to plastic-clay
| >consistency, slightly over-fill each space in the mold,
| >and then tamp down and remove the excess with a
| >putty knife. It's important that you don't remove too
| >much material; an undersized cone will bend at a lower
| >work-heat point.
| >Since the recipes don't have much clay in them, they
| >mixtures are pretty short, but still fine to work with.
| >I used ball clay, with it's inherent impurities, to
| >improve the workability, so this throws my formulas
| >a little off from the theoretical cone formulas.
| >A 100 gram batch makes LOTS of cones.
| >
| >
| >CONE 10
| >
| >Custer feldspar 17
| >Whiting 7
| >OM#4 ball clay 37
| >flint 31
| >(this adds up to 92)
| >
| >CaO .67
| >MgO .03
| >K2O .21
| >Na2O .08
| >Fe2O3 .02
| >TiO2 .08
| >Al2O3 1.26
| >SiO2 10.02
| >
| >
| >CONE 8 1/2
| >
| >I like this cone because it gives me a little earlier
| >warning than cone 9 for my cone 10 firings.
| >
| >Custer feldspar 22.5
| >whiting 9
| >OM#4 ball clay 29
| >flint 39.5
| >(100 total)
| >
| >CaO .69
| >MgO .02
| >K2O .21
| >Na2O .08
| >Fe2O3 .02
| >TiO2 .05
| >Al2O3 .90
| >SiO 8.96
| >
| >--
| >David Hendley
| >Maydelle, Texas
| >hendley@tyler.net
| >http://www.farmpots.com/
|
| |
|
