How does an air classifier separate plastic and aluminum containers from glass?

In a material recycling facility, an air classifier separates aluminum and plastic containers from glass by utilizing the difference in the weight of the materials.1

As the commingled recyclables move along a conveyor belt, the air classifier uses a stream of air to lift the lighter aluminum and plastic containers away from the heavier glass containers. This process allows the lighter materials to be separated from the glass, which remains on the conveyor to be sorted further by hand. Once separated from the glass, the aluminum and plastic are then processed through an eddy-current separator to distinguish the aluminum from the plastic.1