EPK vs China Clay

[GreyBird]

I have a bucket of China Clay and I also have a smaller newer batch of EPK Kaolin which I ordered because I did not realize that they are basically the same thing. I thought they were but wasn't 100% sure so I ordered the EPK to be safe. Then I noticed it is not nearly as white as the China Clay so thought it must not be the same thing and proceeded to only use the Newer EPK. But today I did a Google search and can not find any comparison except maybe particle size. The EPK should fire up very white but they are comparing it to ball clay not China Clay. My EPK looks like the China clay with a bit of ball clay tint to it. Not sure if the color difference shows very well in the photos but does anyone know what the difference would be in the resulting glazes were I to use China Clay vs EPK? The one in the yellow bucket is the China Clay and in real life it is much whiter than the EPK.

[glazenerd]

Mary:

two primary differences in kaolin. The first being particle size, although at cone six and above enough flux will do the job regardless. The second: titanium content. Kaolin is very low in iron and magnesium, but can have low ( china/ grolleg) to much higher levels: EPK, tile #6, helmer. White means low titanium, buff to light tan indicates titanium.

T

 

[neilestrick]

What are you using it for? In a glaze you won't see any difference. In a clay body that has any other type of clay (ball, fire, red, etc.) you probably won't notice much difference. In a porcelain body where it's the only clay, you'll feel a difference. You'll see a difference in color, too, but not as much if you're firing in oxidation.

[GreyBird]

Thanks! I'm using it for mixing glazes so I guess I have a good supply

[Callie Beller Diesel]

A Canadian ex pat friend in Ireland tells me they substitute China clay in for EPK in recipes that originate on this side of the Atlantic with little difference. There will always be the odd glaze that is sensitive to changes in materials, but they tend to be the exception that proves the rule. 

[Mirrored-K-Studio]

What differences have you noticed in the wet mix? 

I recently tried subbing china clay for epk and it looks very rose pink. My older batch where I used epk is strong RED.

I have not had the chance to fire it yet.

[neilestrick]

Did you use the same type of iron oxide in both batches?

It doesn't really matter what the wet mix looks like, only the fired results.

[Dick White]

As others have noted above, there generally isn't much difference in the outcome with EPK and china clay. One glaze where I have noticed some difference is a true iron celadon in reduction. EPK will push the tint towards green while using English Grolleg will tend towards blue. But this is the only time I've seen a difference.

[Mirrored-K-Studio]

thank you all, I wasn't able to check back until now.

 In my experience the wet mix color has not mattered with other glazes. I was just thinking of anything that might be different. 

The Iron oxide I used may have been different, not by name but by decades difference in age.

thanks again

Kyle