When an electric current is applied, the liquid crystal molecules line up, the incidental light passes through, and the privacy glass becomes clear.
Privacy Glass is a laminated glass. The laminated material within is Liquid Crystal Privacy Film, which responds to an electrical current.
When electricity is applied to the film via the wiring, the liquid crystals align and the glass instantly becomes clear. When the power is turned off, the liquid crystals return to their normal scattered positions rendering the glass an opaque translucent.