Fluorescence and phosphorescence are two chemical processes: the absorption and emission of light by a material, in this case pigments. Fluorescence occurs much faster than phosphorescence.  When the excitation source (daylight) is removed, the brightness ceases almost immediately, and the fluorescent markings are not seen to glow in the dark.  Phosphorescence lasts much longer than fluorescence (from a few minutes to several hours and up to a few days after the light is turned off. Phosphorescent or photoluminescent markings do not appear brighter in daylight but are visible in the dark. Our marking product PHOTOLIGHT (Phosphorescent or photoluminescent) has these characteristics.