Photoluminescent signage for low light ambient environment

A method, comprising:

• positioning an exit sign comprising a substrate in an environment to provide an EXIT message to occupants of the environment, wherein the EXIT message comprises photoluminescent letters attached to the substrate, wherein each of the photoluminescent letters comprises a photoluminescent portion and a non-glowing border, wherein the exit sign is not connected to an electric power source, wherein the photoluminescent portion of each photoluminescent letter has a height of at least 170 mm, and wherein the non-glowing border of each photoluminescent letter has a width of at least about 2.5 mm,
• charging the photoluminescent letters with ambient lighting of less than 5 foot-candles for at least 60 minutes, wherein the ambient lighting is provided by any of unfiltered fluorescent lighting, metal halide lighting, mercury vapor lighting, and LED lighting,
• wherein upon removal of ambient lighting from the environment, the EXIT message is readable by occupants of the environment at a viewing distance of 50 feet away from the exit sign as measured along a line perpendicular to the EXIT message and subsequent to the occupants' eyes acclimating for 5 minutes immediately prior to reading the EXIT message.