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Kaolin Substitutions


jammy43

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as you know its not as white, nor as tranluscent

it has different trimming chacteristics as well as drying charteristics

i have been reducing amount of grolleg for cost factor  and replacing PARTIAL amount of kaolin with EPK

firing wise and glaze wise i have yet to see difference

im in florida and epk is pretty much local clay for me you should see my gallery for pictures of edgar mining home of epk.

its a bit grey when wet, and dry in bag, it dries white, and is a bit off white when compared to grolleg based clays. 

i also will use part 300mesh silica, to keep that softer feel and trim feel

i tend to dry epk clay a slower it tends to dry on skin while being wetter under surface

 

im a big fan of epk, prolly have 5 bags in storage right now

if you have more questions let me know

or pm me

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In most glazes you won't see any effect. EPK is slightly higher in Titanium, so that can have a small effect, but for the vast majority of glazes it won't matter.

 

EPK bodies can still be translucent, but for most people that's not an issue anyway. As Biglou said, there will be a slight color difference, but in cone 6 oxidation it won't be nearly as noticeable as in reduction. If your recipes only call for 25%, the other clays in the bodies will already be affecting the color anyway. HERE is an interesting thread from Clayart in which Ron Roy discusses kaolins with some other tech guys. According to Ron, EPK is the whitest of the 4 kaolins they use at Tucker's, including grolleg. Grolleg, however, vitrifies at a lower temperature so you can get more of it into a translucent body than with EPK, which improves workability. Interesting stuff!

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Thanks so much for the info!!  Today I was mixing some glaze tests and there was mention of both grolleg and EPK within some of my test recipes.  EPK I have so that went into the glazes.  Then I came in to 'do my research' via a question placed on this forum!  I'm glad others have the same questions I do and it makes me feel good to know that I have a forum to get answers to my questions.

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Sure Lou

 

I'm looking at using/trying Jeff Campana's porcelain: ( trying to source C&C ball clay in Canada)

25 Grolleg Kaolin
10 C&C ball clay
10 Tile ^ kaolin
35 Minspar 200 feldspar
20 silica 325 mesh
2.5 bentonite L-10 white
 
 
And using Cushing's stoneware recipe:
 
White Stoneware Throwing
Source Cushing's Handbook (#2 p.37)
Name VC Vitreous White
Cone 6
Note White, very strong body
Recipe
Grolleg 25
C&C 25
Kona F-4 30
Frit 3124 4
Flint 16
Macaloid
 
i picked these two for the similarity in materials and therefore cost.
 
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Jammy both of those made my short list, good choices

 

Last body I made was

 

C6 Clay Body - from Val Cushing:

EPK Kaolin 35

Tile 6 Kaolin 15

Nepheline Syenite 23

Flint 22

XX Sagger Ball Clay 5

Bentonite 3

 

I subbed out tile most of tile 6 with grolleg .... I was going for more traditional ish porcelain

 

I'm going to throw some of this tomorrow.

 

I feel using grolleg in stoneware is bit of a waste.

 

Grolleg definitely has a feel to it but I think you can get the same with epk and 300 silica, and slurry mixing.

 

I have - bag I'd c&c I haven't used yet. When I do make my clays I use a slurry method. Which I'm told is superior to standard method. I even end up lowering bentonite in recipes because clay can be "too buttery". Nonetheless im still interested using the c&c. Many here say its night and day difference over other ball clays. Eg om4. #5

 

So I've basically given you a few of my secrets

 

Slurry mix clay

Sub out portion of 200 silca with 325.

Age clay with moldy rag.

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C&C is my favorite ball clay by far. You'll love it.

 

Grolleg is indeed a waste of money in stoneware clays. Just go with a cheaper domestic kaolin. With ball clay and other stuff in there you won't really notice much of a difference in feel or color anyway.

 

I still have a hard time with people calling it porcelain if there's ball clay in it. That's a white stoneware in my book. <_<  

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Jammy both of those made my short list, good choices

 

Last body I made was

 

C6 Clay Body - from Val Cushing:

EPK Kaolin 35

Tile 6 Kaolin 15

Nepheline Syenite 23

Flint 22

XX Sagger Ball Clay 5

Bentonite 3

 

I subbed out tile most of tile 6 with grolleg .... I was going for more traditional ish porcelain

 

I'm going to throw some of this tomorrow.

 

I feel using grolleg in stoneware is bit of a waste.

 

Grolleg definitely has a feel to it but I think you can get the same with epk and 300 silica, and slurry mixing.

 

I have - bag I'd c&c I haven't used yet. When I do make my clays I use a slurry method. Which I'm told is superior to standard method. I even end up lowering bentonite in recipes because clay can be "too buttery". Nonetheless im still interested using the c&c. Many here say its night and day difference over other ball clays. Eg om4. #5

 

So I've basically given you a few of my secrets

 

Slurry mix clay

Sub out portion of 200 silca with 325.

Age clay with moldy rag.

Big Lou  I also slurry mix and use silca 325.  but I'm interested in what you mean by "age clay with a moldy rag" ?   I'm thinking that you are wrapping clay in a moldy rag to get some organics in there.

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Yep, old rag

It dries out I put in plastic bag , moisten then use next batch.

If your's doesn't work I'd be willing to cut a piece off so you can inoculate yours.......

I'm wondering if specific clays needs specific mold/s.

It could all be old wives tales, but It seems to work and much faster than sitting around clean....

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