...Reuse, Recycle

From January, 2010. For the record, duct tape actually worked...


Do you remember the scene in Fiddler on the Roof where everyone is fluttering about the "new arrival" at Motel and Tzeitel's house? The crowd finally parts to reveal Motel showing off his new treadle sewing machine—while a still very pregnant Tzeitel walks in from stage left.

Well, this is our new arrival: a Venco 4-inch de-airing pug mill. It mixes and screens recycled scrap clay and runs it past a vacuum pump to remove air bubbles before extruding a nice smooth cylinder ("pug") of clay.

I bought it second-hand last November from a potter who's now doing mostly bronze sculptures, and had to wait until after the holiday rush to get it running. We spent a week tearing it down, cleaning out a decade's worth of dry porcelain scrap and putting the pieces back together, meanwhile rewiring the studio and building a bench around it to replace the lost work space. It was a heavy work; the thing weighs well over 500 pounds, so just getting it down from West Linn to Eugene involved wheels, ramps, and the assistance of another potter from Club Mud who thought he was getting a good deal on free lunch and a round-trip ride to Portland. (Thanks, Don. Hope the back has recovered…)

Tricky, too. Venco is an Australian brand, and half the bolts were metric, half English. A few were also corroded tight. Fortunately for me, my neighbor is a retired log truck driver with some big power tools, including an impact wrench that finally did the trick.

How does it work? Well, we're still working on that. We've run it twice so far, and the mixing and extrusion parts work fine, the de-airing not so much, possibly from air leaking in through the side seams. If we can get them tightened up, there ought to be vacuum pressure. I'm thinking duct tape.

Terminus

Pug mill. A clay mixer. An auger in the tube mixes the clay thoroughly and forces it through a screen that catches foreign objects and cuts into air pockets. A vacuum pump de-airs the clay and the auger compresses and extrudes it again. I use mine to recycle scrap clay; some people run all their new clay through as well, rather than wedging by hand.

Pug. Clay extrusion from a pug mill. Duh.

Drying bat. Tub for drying out wet clay scrap for recycling. The simplest of these are made from cast plaster, but I don't like plaster in the studio, as scraps in the clay will cause bits to pop out after firing. My drying bat is a rectangular frame made from 2x6" pine, with a bottom made a layer of plastic window screen supported by 1/4" hardware cloth supported in turn by 1x2" strips. The whole thing is mounted on heavy duty casters to roll in and out from under my ware racks. I line it with an old bed sheet, fill it with wet scrap and fold the sheet over the top. In a couple of weeks, it's dried to a firmish mass that I can cut into blocks and run through the pug mill.

Wedging. A process of cutting up clay and slamming it on the table top, followed by kneading. This mixes wet and dry clay thoroughly, removes air pockets, and aligns the clay particles to make a denser, stronger body. I used to recycle all my scrap clay this way, before I bought the pug mill. Exhausting.