Invisible ink is a writing fluid that’s invisible when utilized to paper however could be revealed later by warmth, gentle, or chemical response. It has been used for hundreds of years to ship secret messages, and it’s nonetheless used in the present day for quite a lot of functions, together with safety, espionage, and leisure.
One of the frequent methods to make invisible ink is to make use of lemon juice. Merely write your message on a chunk of paper with a lemon wedge, and permit the juice to dry utterly. The message will likely be invisible till it’s heated, at which level the lemon juice will caramelize and switch brown, revealing the message.