Your glass needs to be exposed to light in order to glow in the dark. Some pieces have more glow in the dark material then others as well. The glass only glows within itself, it will not give off light. Make sure its in a room with windows during the day and it should glow for an hour or more at night. It will charge by artificial light but it does not tend to hold the glow in the dark effect as long as natural light.
18th May 2015