Pug Mill

What it is

A pug mill takes lumps, trimmings and reclaimed scrap, pushes them through an auger and extrudes a dense, de-aired log from the far end. The vacuum chamber is what separates a pug mill from a simple extruder: by pulling air out of the clay under vacuum, the machine produces a body with no trapped pockets at all.

For a shared studio or a production potter, the economics are obvious. Wedging 20 kg by hand takes half an hour and hurts; a pug mill does it in three minutes and returns a more consistent log. Reclaim — the bucket of slop under every wheel — becomes usable stock again rather than landfill.

Two families dominate. Vertical pug mills take up less floor space and are easier to feed; horizontal mills handle larger volumes and blend dry colourants or grog more evenly. Almost all models let you fit a die at the outlet to extrude coils, tiles or hollow tubes as well as plain logs.

How to use it well

• Feed in small handfuls and let the auger draw the clay down; forcing material in causes jams.
• Blend reclaimed slop with dry trimmings to reach the right consistency before feeding — the mill is a mixer, not a dryer.
• Fit a vacuum gauge and watch it: a falling vacuum means the seal is leaking and the clay is not being de-aired.
• Empty the barrel before any break longer than a fortnight, or the clay will set like concrete inside it.

Safety notes

• The auger will not stop for fingers. Never reach into the hopper while the mill is running or plugged in.
• De-energise and lock out before clearing a jam — the classic injury is a hand caught when the blockage releases.
• Extruded clay is dense and heavy; lift logs with a partner or a trolley, not your back.

Compatible materials

Clay bodies

• Stoneware
• Earthenware
• Porcelain
• Reclaimed blends

Glazes & surface

• Not applicable — preparation equipment

Where it sits in the process

Preparing and homogenising clay before forming.

Wedging  Clay & Preparation  Pro tier

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