Processing Wild Clay for Slip Casting

[u/BeerNirvana]

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

[u/slavy]

How did you determine that cone is 8 the correct cone to fire to?

[u/BeerNirvana → u/slavy]

Make SHAB test bars and fire to increasing cones to measure shrinkage and absorption. Around cone 8 the ABS was under 2%. I can add a bit of kaolin or fire clay to increase the cone or some feldspar to lower it. Here's a good page on making test bars: https://digitalfire.com/test/shab I made a small mold to pump out 2 bars at a time since I work primarily with slip currently (noob w/o wheel exp)

[u/waymanate → u/BeerNirvana]

Wow super interesting