As a kid, you may remember wearing a watch that would light up at the push of a button. This nifty feature allowed you to tell time in the dark; That glow was the watch's lume. "Lume" is short for the luminous material on watch dials - usually found on the hands, hour markers, and even the bezel. The most common application is a phosphorescent solution that is charged by light. In timepieces nowadays, the presence and intensity of luminescence on a wrist watch is considered to be a premiere, must-have feature. Lume is also considered to be an integral part of the design, even though it is not visible in the light. A brief poll on WatchFreeks reported that 50% of participants thought it was “a nice feature but not a deal breaker” while over 35% responded that it was “very important and a must." Lume used to be radioactive! Originally in the early 1900s, radioactive material like radium mixed with zinc sulfide was coated on watches to give them a glow. Of course, this was eventually found to be an unsafe practice. Today the most common material used for lume is a non-radioactive pigment or solution that is charged by light. While lume is available in a variety of colors, in the light its presence may go unnoticed on the dial. In some cases however, based on the color of the glow, it may possess a slight tinge of green or blue. Heavy amounts of luminescence are not common to classic or dress watches; however some do have small amounts applied to the dial or hands. Sport and diver watches predominantly feature the most amount of lume. Strong lume is one of the most important attributes of a dive watch, which is essential when diving to lower depths or in very turbid water. It's important for divers to keep track of how long they’ve been submerged, as it pertains to the amount of oxygen left in the tank. A diver watch like Orient's M-Force Beast or 300m Pro Saturation Diver are not only known for their robust case structure, but also for their lasting and reliable dial lume. A sport watch like the Pilot's Watch has also been lauded for its brightness in the dark and superb legibility. So whether it’s for a diving adventure, or to check the time in a dark movie theater, or glancing at the time on your night stand - the lume on watches definitely has its purpose. Functionality aside, the added style that lume adds to a watch, is important to both timepiece enthusiasts and the casual watch wearers. Be sure to check out Orient’s variety of watches with lume here.