How long do glow in the dark stones last?

Bright – The brightness and duration of the glow in the dark material in glow in the dark stones we use is more than 10 times brighter than traditional ZnS (zinc sulfide) luminous material. Efficient – With only 10-20 minutes of exposure to daylight or lamplight, the CORE Glow™ products can maintain its afterglow in the dark for about 10-12 hours.