Imagine an ink that you write something on paper, and is at least partially invisible at first, and over hours or days has a chemical reaction with the air and becomes visible.
Does this type of delayed invisible ink exist? How would you make it?
Imagine an ink that you write something on paper, and is at least partially invisible at first, and over hours or days has a chemical reaction with the air and becomes visible.
Does this type of delayed invisible ink exist? How would you make it?