The same pugmill (back and front). One is stainless steel. Potters claim that they can dump almost anything into these machines (even dry scrap) and as long as they add the right amount of water the devices will mix and vacuum extrude a finished slug. Considering how portable these are they are an amazing device. However, these are no match for a large industrial pugmill. In the quantity of material they can produce, but also in the quality. They have few or even no blades on the main shaft, only augers. They contain no or only a rudimentary shredder feeding the vacuum chamber and little dwell time in the both chambers.
The practice of removing air from clay as it is pugged. Deaired clay has better forming properties and produces a smoother fired surface.