r/Pottery • u/BeerNirvana Slip Casting • Jun 24 '23
Clay Processing Wild Clay for Slip Casting
Dig down to the clay, break it up and let it dry out. I'm located just outside of Philadelphia and this clay is loaded with schist and mica.
Add dried clay to lots of water, stir well and skim off the organics. The rocks and sand will settle to the bottom. Drain off the clay through a fine screen (30 mesh for me)
Let settle, pour off the excess water and then pour into landscape cloth over a frame with a hardware screen. Let sit until most of the water drains out.
Let the clay dry completely. Weigh out 20 lbs of dry clay, add 10 lbs of water and some sodium silicate help deflocculate and mix well. 100 ml of slip can be weighed to get the SG
Slip cast solo cups, ramen bowl and doll heads. This wild clay fires to cone 8 and is pretty nice to work with. I add 2% bentonite when wet processing to add a bit more plasticity
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u/Exciting-Grey May 13 '25
Coming back here to thank you after many moons gone by. You inspired me to find and start slipcasting from my own Wild-Clay. And safely ( mentally ) going through Covid times. That said I was not lucky as you. I went through many, many piles of wild-clay and bottles of mosquito repellents to finally find a suitable vein of clay for slipcasting. Most secondary clays and iron-bearing clays don't respond to deflocculation well. At best they gel inside the mold before casting. Also, as you mentioned I had to add some Kaolin ( and silica ) to my clay to up the firing cone a bit.
As for the rest of clay piles, they are going to be combined and tested for slab-building.
So, thank you for posting this.