There are a couple of tips for glow-in-the-dark cups that we’d love to share with you. The glow-in-the-dark green and purple cups should be “charged” under direct sunlight or artificial light for at least 30 mins, (2-3 hours for maximum glow) For optimal glow, charge under direct light. Please keep in mind, leaving the cups outside without direct sunlight will not provide sufficient direct light for charging. The way the tumbler needs to be charged is different. The glow-in-the-dark blue requires natural light ( light bulb), while glow-in-the-dark green requires UV (sun) light. The suggested time for the initial charge is 3 hours or more. The better you charge, the better it glows!
