A kind of variable transmittance glass, electrochromic glass works in a way similar to suspended particle devices (SPDs), but generally uses lithium ions instead of nano-particles, and does not require sustained voltage to maintain the change in the glass. When electrochromic glass is activated, a single burst of electricity is dispersed and the look of the glass changes, even after the electricity has dissipated. The glass will retain that specific look—be it transparent or translucent—after the electricity no longer is provided to the unit. A second burst of electricity is required to change the glass back to the original state. Electrochromic glass does not change instantly or evenly; the change is often first noticeable on the sides first and moves toward the center. The time it takes to complete the change from one look to the other can depend on the size of the glass and some electrochromic glass provides a certain amount of limited visibility in its darkened state.