Clay Tests 2022-24

This document records multiple clay tests that I performed while at IU Southeast. Each section will dictate my desired outcomes, approach, and test results with feedback notes.

GH Wood, Post-Baccalaureate 2022-24, ogwood03@gmail.com

Clay Bucket Recipes Derivatives

Sandy White Stoneware

I admired how this clay body responded to the soda firing. However, I wanted to emphasize the rich reds left around the wadding marks and to transpose them to the rest of the form. This led me to try experimenting with more iron rich sources of clay because I believe it would shift the color range away from the kaolin orange and gray and more towards reds. The following tests were fired in the IUS soda kiln where 2 lbs of soda ash was sprayed at peak temp, with a final reduction post exposure.

This round of experimentation resulted in a nice color range of orange to red. However, all clay bodies still developed a lot of soda glaze that pitched gray. This is the result of many factors but the ones I’ve discerned are: 1) kiln size = tighter flow of soda, 2) soda ash has 50% more soda introduction than soda ash / baking soda, 3) higher percentage of kaolin develops the gray glaze. Overall, a good starting point for more red stonewares. The stand outs that I would consider pursuing more are tests # 2 and #3.

SW #1

Substituting EPK for Helmer Kaolin, a higher iron source kaolin
Nice oranges with hints of deeper reds
Soda glaze still significantly accumulated around the kaolin rich body
Nice to throw with, but can easily flop when thrown to thin

SW #2

Helmer Kaolin is tougher to work than EPK based recipes, so I included tile #6 to help with workability
Introduction of lizella clay instead of goldart to increase iron content
Minspar 200 was utilized to try to decrease the Silica:Alumina ratio to hopefully promote more flashing and less soda glaze formation
Developed a nice red from minimal to no soda contact
Still developed a bit of soda glaze, could be combated through less soda introduction
The introduction of lizella created nice iron spotting more reminiscent to stonewares

SW #3

Playing with Helmer and Tile 6 ratio to maximize nice flashes and workability
Redart utilization because of its accessibility, mixed with goldart to prevent over firing at cone 10
Nice reds were achieved, leaned a little more purple

SW #4

Utilization of Newman substitute to really increase iron source
The soda glaze developed a nice iron pitch (leans more green/orange highlights)
A red range that lends itself more towards browns
Goes really dry when exposed to little to no soda, needs a light soda spread for nice surface

SW #5

A full 1:1 substitution with the key ingredients of kaolin, stoneware clay, and flux
Developed light red and leaned more towards orange

Levin Porcelain Derivatives

I really liked the flashing occurring with LP while still achieving a nice white background when covered with a glaze. I wanted to promote more flashing and a wider range of colors by playing with the iron source. These tests were fired in the IUS soda kiln where 2 lbs of soda ash was introduced followed by a heavy reduction soak at the end.

Not the most fruitful experimentation. I did not achieve any new coloration range, I may have even limited it. Test #4 had some interesting results, but ultimately proved fruitless with how dry it became with little soda exposure. I learned a drastic increase in iron would be needed to really change a porcelaneous body. The use of grog and sand gave similar results, but the sand produced brighter spotting marks. No further development of these bodies.

LP #1

A nice orange range of colorations
Hints of carbon trapping present
Really glassy surface

LP #2

Nice to work with on the wheel
Lizella darkened the oranges, but we’re still in the orange range

LP #3

Heavily exposed to the soda atmosphere wiped away most flashing
What little flashing marks are left are a nice orange

LP #4

A really dry body
Nice flashing
Soda glaze pitched in the iron range
Hints of carbon trapping
Grog detracts from the nature of this “porcelain”

LP #5

Surprisingly the newman red did not affect flash coloration as much as anticipated
Newman red and lizella lead to similar surfaces
Quite dry and rough to the touch due to sand

Iron Doped Porcelain

Looking for a porcelain body that will pitch white when glazed, but still develop a nice red range flash when raw. Tile #6 and Helmer were used for their workability and flashing. I ran a suite on iron rich clays with the same base recipe, which was initially developed with goldart. These were fired in the IUS soda kiln where 2 lbs of soda ash was introduced and a heavy reduction soak happened at the end.

This was my most fruitful clay exploration for my high-fire clay body recipe. The first suit of 4 are closer to a b-mix while the later half are more porcelaneous. Recipe number 7 was further developed and has become my go to recipe.

IDP #1

A nice red range of color, again redart leaning more purple
Was easy to work with on the wheel and handbuilding
Did not develop a gray glaze surface

IDP #2

A nice orange range of flashing
Minimal gray glaze development
I think the larger particle size of lizella leads the clay body being more difficult to work with, may want to grind down

IDP #3

Dunted
A dark red stoneware, more browns than red

IDP #4

Dunted
Dark red stoneware

IDP #5

A nice porcelain recipe
Easy to work with
Nice orange flash with hints of darker reds

IDP #6

A little short, most likely due to the lizella
A nice orange flash, no dark reds present
Nice carbon trapping

IDP #7

A really nice dark red flash with a deep orange flash
Really nice carbon trapping capabilities
Easy to work with

IDP #8

Really deep reds, nice orange flash with less soda coverage
Heavy carbon trapping on rim and graying

Joseph Pintz – Raw Earthenware Clay Body

Brian Harper was talking with Pete Pinnell about a native Nebraska iron rich clay. He worked with Joe Pintz to get a sample of the clay. I had been looking for a nice red range clay and was curious about lower firing ranges. I used this existing recipe to test out the endicott and to get better acquainted with lower firing temps.

A really nice earthenware clay body to work with
Malleable and able to be stretched far
Grog is very apparent and easily breaks through surface
Grog does create nice iron spotting
A nice red and orange color range
Easily absorbs glazes and it seems to even seep through from interior to exterior
Barium carb is crucial

Pete Pinnell Earthenware

In tandem with testing Joe Pintz and Alfred Yixing imitation, I tested out this clay for constructing gongfu style teapots.

Nice to work with
Bright orange to dark brown range
Really smooth

Alfred Yixing Imitation

I have been really interested in gongfu style teapots and the claybody used by Yixing potters. I found this imitation from Alfred Grinding Room and tested in tandem with other mid range and low fire clay body recipes.

Nice to work with
This is a really tight clay body and shrinks significantly
A rich brown color, really needs to be burnished in order to get a nice surface

Red Stoneware Exploration

After testing existing recipes, I wanted to look around for other mid-range recipes. Looking for a nice red clay body and less brown. I was curious about the cone 3 to cone 6 range. These were fired in an electric kiln. Interested to see how a reduction kiln affects the color and integrity. This is to discern a similar color to endicott clay without access to endicott clay

Look at ranges of clays that utilize redart as a base and then pitch color with stonewares/fireclays

Lizella – Goes from light yellow to dark orange

C-Red – goes from orange to dark red orange

Newman – orange to deep orange

Laterite – brown red and darkens to red

Redart – red to brown

Endicott – red to brown, too, but transitioned at hotter table

A nice red is achieved by dousing a redart clay body with a redder base. I utilized c-red because there is little evidence of it going

RSE #1

A nice clay body to work with
Cone 3 yielded a nice red, does not look like bisque which was an issue with the previous tests
Cone 6 yielded a nice dark red with hints of brown.

RSE #2

A nice smooth body that ranges more on the purple brown range
The cone 3 and 6 yield a more brown hue than the desired red

RSE #3

Really groggy and hard to yield a nice clean surface
Cone 3 has a nice red but it is lost at cone 6
There are hints of red at 6 but it is more brown dominant

RSE #4

A pure clay test to understand how this affects the undertones of other clay bodies
A nice red and orange range that is darker than redart
More red and less purple than redart

RSE #5

Joe Pintz recipe, look at that section to see conclusions

RSE #6

Gave a lighter red at cone 3 but a darker purple brown at cone 6
Grog really interfered with surface finishing

Finalized Clay Bodies

Red-Black Stoneware

This was a reformulation of the cone 6 red stoneware and to try to make it more of a b-mix than a stoneware. This is only a theoretical recipe and has not been tested. A similar recipe was tested in wood and soda. It yielded a dark brown surface with hints of red.


Helmer Kaolin	25
Tile #6	15
Lizella	15
C-Red	15
Minspar	15
Pyrophyllite	10
Kyanite	5

Iron Laced Porcelain

This was my go to recipe for my last semester at IUS. This is a very sensitive clay body that needs extra care in firing. This recipe was formulated for soda and wood firings. This body does well in a heavy reduction atmosphere as it helps darken flashing to reds and encourages carbon trapping. A heavy reduction around 1750 helps yield preliminary carbon trapping, a reduction atmosphere soak at peak temperature post spray helps reduce pale colorations, a light to heavy down fire darkens the entirety of the clay body. When this clay is covered in glazes, it acts like a dirty porcelain body and gives a nice white background that is slightly gray. This helped create a nice symbiosis of glazed and unglazed areas across a pot.


Helmer Kaolin	30
Tile #6	10
Newman Red	10
Minspar 200	25
Silica	25
Bentonite	2%

Red Cone 6 Stoneware

A nice red mid-range stoneware that yields a nice dark red surface that gains a bit of sheen when burnished. Throws nicely and hand-builds well. Easy to smooth over and burnish.


Redart	50
C-Red	15
Lizella	15
OM 4	10
Silica	10
Bentonite	2
Barium Carbonate	2


Helmer Kaolin	40
Goldart	28
Minspar 200	16
Silica	12
Sand	4


Helmer Kaolin	40
Lizella Clay	28
Minspar 200	16
Silica	12
Sand	8


Endicott Clay	70
CC Red	12.5
Redart	12.5
Wollastonite	5
Native grog	15
Barium Carb	1


Endicott	70
CC Red	12.5
Redart	12.5
Wollastonite	5
Native grog	15
Barium Carbonate	1

The Claybucket

at IUS Ceramics

GH Wood’s Clay Tests 2022-24