Wow mugs are coated with a special heat reactive paint. When the mug is cold the image is obscured. But when the mug is filled with hot liquid, the image is revealed. As the mug cools the image starts to disappear. Not only is the Wow mug a great gift or just something fun to show friends, it is also a practical way to know how hot or cold your drink is. Also available in dark Blue or Green. £5.99 Promotional or personalised for business or otherwise