[Clayart] Ball Clay - using it in a glaze?

Robert Harris robertgharris at gmail.com
Wed Jul 6 11:51:13 EDT 2016


My take on it is that the lichenification is more to do with the physical
properties of the slop (subbing OM4 for EPK is like adding a bunch of
bentonite). I imagine you got lots of cracks in the dry glaze. Basically
you're getting crawling because of dry, room temperature glaze fit (not the
usual post firing glaze fit which we talk about)

This sort of substitute works best when EPK is less than 10% (or maybe
15%). Any more than that and yeah, you need to test!

Generally ball clays have more silica and less alumina than kaolins (4:1 vs
2:1 approx). This lead to the sort of things Tommy talks about.

On Tue, Jul 5, 2016 at 5:23 PM, Dan Saultman via Clayart <
clayart at lists.clayartworld.com> wrote:

> Some time back Mel and a few others claimed that they liked to substitute
> half of the EPK in a glaze for Ball clay. (cone 10 is my temp.)
> The idea was that the ball clay caused the glaze to fit better and was a
> solution for crazing.
>
> I therefore used ball clay in a few of my glazes as suggested - disaster.
> The ball clay was much more refractive and caused glossy glazes to bead up
> like a lichen glaze. Not so good when you are using it for a white liner
> glaze.
> I thought that I could trust such a simple substitute since I don't have
> the time to run extensive tests. But alas. Ball clay was not a simple and
> easy substitution.
>
> I am only mentioning this to you so that you may avoid the pratfalls of my
> mistake and trusting ways.
> In the end - everything needs to be tested. I ruined a huge bucket of
> glaze thinking it was a minor tweak. Not so.
> I also lost a dozen pots that were part of an order.
> God, when will I ever learn.
>
> Dan
>
> Dan Saultman
>
> Fine-Art Pottery & Tile
> ETSY Shop: http://www.etsy.com/shop/DanSaultman
> Clinton Township, MI
> http://www.saultman.com
>
>
>
>
>
>
>
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>


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