Tweaking a Clay Body: Part One
We are going to just jump right in here. No back story, no preface. This will be part one of x number of clay tweaks I will ultimately document here. I was mixing clay today, and when I do that, I think about how I can improve my clay in some aspect. That, to me, is the whole point of doing the clay formulation in the first place. My clay is great, don’t get me wrong. It fits my glaze, allows me to do all kinds of crazy things to it, like cut it apart and stick it back together, and looks fantastic (pure white in electric firings). It is dense and vitreous at Cone 7, which is my target temperature. The one thing I would change is to make it more plastic, and usable right away, straight out of the mixer. My current clay is great, assuming it has aged for a couple months. This is the recipe starting point.
Campana White Midrange ^6-7 Ox
10 Tile 6
35 KONA F-4 Feldspar
Now, when I mix it, I use about 100 pounds of reclaim, and add 150 pounds of dry material. I’m usually pretty close dryness-wise and don’t need to add a lot of water, which means, I can’t blunge the bentonite. I dry mix it in. I think that the reason it needs to age, is that I need to wait around while the bentonite activates, lending plasticity. I have decided to try sourcing some more of the plasticity from the OM4 ball clay, adding it at the expense of the less plastic EPK. I estimated that 5% should be a big enough jump for me to feel the difference. I then took out 1% of the bentonite, as to not make it shrink in the drying way too much. So the new version is:
Campana White Midrange v2 ^6-7 Ox
35 Kona F-4 Feldspar
So far, it feels good. I did the coil-around-the-finger test, and it passed with flying colors. A coil the thickness of my finger wrapped completely around my finger without cracking, fresh from the mixer! I will put it to the real test as soon as I run myself out of the old stuff.
The worries here would be:
- That the shrinkage has increased and will crack my pots apart in the drying.
- That the addition of OM4 will make it slighlty yellow and riun the pretty bright glazes I have
- That the glaze somehow doesn’t fit anymore.
These sorts of risks are worth it, in my opinion. Nothing ventured, nothing gained!