... brightnessabsorb any kind of visible light(sunlight, lamplight, etc.) for 15 minutes , then continuously glow in the dark more ... photoluminous safe signs:road instruction signs, road safety signs, ship safety instruction signs, fire safety signsusages of photoluminous signs:evacuation passage, ... printing ink, can glow in the dark palce for over 12 hours light and absorption of sunlight, lighting ...