Greg Lamont on sun 17 aug 97
Hello all,
I'm hoping one or more of you fine clay gurus out there can help me
reformulate this clay body. It is the main clay body that ceramics students
at Iowa State use for general-purpose throwing and handbuilding and is
designed for cone 9-10 reduction.
I like the body very much and would like to keep using it, but I have begun
doing most of my firing at cone 5-6 oxidation. The body is not fully mature
at this temp. causing almost invisible crazing to occur. How might I alter
this body to lower its maturation point to cone 5-6? It fires to a very
light pinkish-buff color in oxidation. What might I add to darken it to a
light to medium brown?
50 lbs. Cedar Hts. Goldart stoneware clay
50 lbs. Hawthorne Bond fireclay (35 mesh)
50 lbs. KY OM#4 ball clay
5 lbs Silica sand (90 mesh)
10 lbs. Silica flour (325 mesh)
10 lbs. Custer feldspar
5 lbs. Redart
5 lbs. Grog (35 mesh)
5 lbs. Kyanite (100 mesh)
Your help is greatly appreciated,
Greg
Jonathan Kaplan on mon 18 aug 97
>----------------------------Original message----------------------------
> most of my firing at cone 5-6 oxidation. The body is not fully mature
>at this temp. causing almost invisible crazing to occur. How might I alter
>this body to lower its maturation point to cone 5-6? It fires to a very
>light pinkish-buff color in oxidation. What might I add to darken it to a
>light to medium brown?
>
>50 lbs. Cedar Hts. Goldart stoneware clay
>50 lbs. Hawthorne Bond fireclay (35 mesh)
>50 lbs. KY OM#4 ball clay
>5 lbs Silica sand (90 mesh)
>10 lbs. Silica flour (325 mesh)
>10 lbs. Custer feldspar
>5 lbs. Redart
>5 lbs. Grog (35 mesh)
>5 lbs. Kyanite (100 mesh)
>
>Your help is greatly appreciated,
>
>Greg
For starters, drop the kyanite. I would increase the spar and the fint, and
substitute pyrophyllite for a portion of the flint. Formulated on the basis
of 100 percent, the above body is
Original Cone 9-10
Goldart 26.3
Hawthorne 26.3
Old Mine 4 26.3
Silica Sand 2.6
Flint 5.3
Custer 5.3
Red Art 2.6
Grog 2.6
Kyanite 2.6
total batch 99.9
This is a body of 78.9 plastics and 21.1 (or so) non plastics
Basically, plastic bodies can be grouped as 70/30, 80/20 or some
permutation there of. Even 90/10 bodies can work, So can 100/0. Stay away
from 60/40, and 50/50 bodies are a good place to start for casting
compostions. In my experience, throwing/jiggering bodies work well in the
70/30 range, although remember that these are just my opinions and not
dogma.
New Body for cone 5-6
Goldart 14
Hawthorne
(use 50 mesh) 26
Old Mine 4 20
Red Art 10
Flint 10
Spar 15
Pyrophyllite 5
total batch 100
The Red Art with the flint and spar will help lower the maturing point of
the body. The increased percentage of Red Art will help darken the body.
Remember that this is only a starting point. Please test for shrink and
absorption before you mix. Also,if this works for you, send a bar to Orton
for a DTA test.
Add over the batch, what ever percentage grog you may want. The sand will
have some effect on the melt, but it does add tooth. If it were me, I would
eliminate both the sand and the grog, and substitute whatever percentage
you wish of Mulcoa, a calcine of constant compostion available in many mesh
sizes from CE Minerals.
Good Luck. Keep the list posted on what works for you.
Jonathan
Jonathan Kaplan http://www.craftweb.com/org/jkaplan/cdg.shtml
http://www.ceramicsoftware.com/education/clay/kaplan1.htm
jonathan@csn.net
Ceramic Design Group Ltd./Production Services Voice:
970-879-9139 POB 775112
FAXmodem: same
Steamboat Springs, Colorado 80477, USA CALL before faxing
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(please use this address for all UPS, courier, and common carrier
shipments)
Ron Roy on mon 18 aug 97
>----------------------------Original message----------------------------
>Hello all,
>
>I'm hoping one or more of you fine clay gurus out there can help me
>reformulate this clay body. It is the main clay body that ceramics students
>at Iowa State use for general-purpose throwing and handbuilding and is
>designed for cone 9-10 reduction.
>
>I like the body very much and would like to keep using it, but I have begun
>doing most of my firing at cone 5-6 oxidation. The body is not fully mature
>at this temp. causing almost invisible crazing to occur. How might I alter
>this body to lower its maturation point to cone 5-6? It fires to a very
>light pinkish-buff color in oxidation. What might I add to darken it to a
>light to medium brown?
>
>50 lbs. Cedar Hts. Goldart stoneware clay
>50 lbs. Hawthorne Bond fireclay (35 mesh)
>50 lbs. KY OM#4 ball clay
>5 lbs Silica sand (90 mesh)
>10 lbs. Silica flour (325 mesh)
>10 lbs. Custer feldspar
>5 lbs. Redart
>5 lbs. Grog (35 mesh)
>5 lbs. Kyanite (100 mesh)
>
>Your help is greatly appreciated,
>
>Greg
Hi Greg,
You will have to prove this out by testing - hand mixed samples will not
melt as much as machine mixed so you will have to allow for that.
First of all you don't need all that silica so drop the 325m to 5.0.
To get more melt - up the Red Art in test #1 to 10, in test #2 up it to 15.
I don't think it would be wise to add more than that because it is too
variable. What you are looking for - at cone 6, is a fired absorbency of 1
to 2% and a shhinkage of about 12%. If it is still too open with 15% Red
Art you will need to start increasing the spar -1% at a time.
If you need clarification of anything here I am.
Ron Roy
Toronto, Canada
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
Andrew & Laura Conley on mon 18 aug 97
To darken the clay and reduce the maturing temperature, I would try increasing t
amount of REDART in your recipe. Redart matures at a lower temperature and has
a lot of iron in it. You will probably have to add quite a bit more to achieve
the results you want - but be careful, your glazes may not fit quite right
afterwards...
lconley@dcds.edu
Greg Lamont wrote:
>
> ----------------------------Original message----------------------------
> Hello all,
>
> I'm hoping one or more of you fine clay gurus out there can help me
> reformulate this clay body. It is the main clay body that ceramics students
> at Iowa State use for general-purpose throwing and handbuilding and is
> designed for cone 9-10 reduction.
>
> I like the body very much and would like to keep using it, but I have begun
> doing most of my firing at cone 5-6 oxidation. The body is not fully mature
> at this temp. causing almost invisible crazing to occur. How might I alter
> this body to lower its maturation point to cone 5-6? It fires to a very
> light pinkish-buff color in oxidation. What might I add to darken it to a
> light to medium brown?
>
> 50 lbs. Cedar Hts. Goldart stoneware clay
> 50 lbs. Hawthorne Bond fireclay (35 mesh)
> 50 lbs. KY OM#4 ball clay
> 5 lbs Silica sand (90 mesh)
> 10 lbs. Silica flour (325 mesh)
> 10 lbs. Custer feldspar
> 5 lbs. Redart
> 5 lbs. Grog (35 mesh)
> 5 lbs. Kyanite (100 mesh)
>
> Your help is greatly appreciated,
>
> Greg
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