Making hidden things visible by putting the finger on it. Thermochromic colour makes this magical effect possible.
The surface that looks dark at first sight becomes transparent through the impact of heat and so the underlying motif can be viewed. You can repeat it as often as you want because thermochromic colour becomes intransparent again once after a while. Your advertising message will be noticed again and again. By the way this sustainable effect can be combined with scent printing. Thermo colour is often used for admission tickets, VIP cards or vouchers because a copy can never imitate this effect.