The first pug mills were powered by horses and mules.
The word “pug” means “to mix with water to make it more elastic.” The pug mill, then, is a machine used to grind and mix wet and dry materials, usually for clay, asphalt, and similar compounds. Generally, a pug mill consists of a bowl and one or more rotating arms with blades or paddles on them. They act like a blender, producing a smooth, moist mixture that is easy to work with.
The pug mill has been around since at least the early 19th century. Initially, it was powered by horses or mules. Electric pug grinders have become commonplace in the industry, although the basic design remains similar.
Potters trust these blenders to simplify the process of making and recycling clay. The clay can be mixed from scratch in a dedicated mixer or in a combination mixer/pug mill. Used clay can also be added to the mill to be reincorporated. Once the clay is mixed, the mill is used to create a uniform consistency and moisture level. A good grinder, or one with a vacuum component, can also remove most of the air from the clay, preventing bubbles from creating fine stains on the finished work.
Asphalt manufacturing at this plant generally requires closer supervision than clay manufacturing. The blades of the mill must be very close to the sides of the container so that none of the particles added to the asphalt escape from the mix. Also, the mill must be accurately filled to ensure proper mixing of the materials. The speed and duration of the mix are also critical. Asphalt mixed too fast or slow may not have time to homogenize, while asphalt mixed too fast or too fast can lose some of its durability.
Pug factories vary greatly in size, power, capacity and configuration. Some have propeller-shaped mixing paddles, while others use easily replaceable paddles attached to a mixing rod. In addition to those intended for mixing clay and asphalt, mills can be made to mix chemical or agricultural compounds.
People should be careful when cleaning or repairing a pug grinder or removing pug materials from the grinder. Some materials are quite heavy and are better suited to a pug mill with an extruder than one with manual removal. Also, this grinder can be a powerful machine and can cause serious injury if used incorrectly.