We provide you the invisible ink to make your own unique marks. You can write marks on the paper or plastic cards. UV and IR invisible ink are available now. The marks written by hands are different from those printed by printers. Hand-made marks can only last for 25-30 minutes while those made by machine can even keep for 2 years.
It is a kind of special invisible ink, which is used to mark playing cards or any other paper products.
Applying a little ink on the surface of cards, and you can wait until it gets dry. Then you will see the marks you made personally with our special contact lenses or sunglasses.