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Invisible ink, also known as security ink or sympathetic ink, is a substance used for writing, which is invisible either on application or soon thereafter, and can later be made visible by some means, such as heat or ultraviolet light.
Aburidashi is a ninja technique of sending secret messages using a form of invisible ink. [1] The technique uses ink made of juice extracted from soaked and crushed soybeans . [ 1 ] The message becomes visible to the recipient by heating the paper.
[3] A series of "empty" boxes located below or following the text contained the answers, printed in invisible ink. The contents of each box could be revealed by using a highlighter-like marker that came with the book. [1] Over time, the ink degraded and the text reverted to invisibility.
UV marker with UV led lamp. An ultraviolet (UV) marker is a pen whose marks are fluorescent but transparent; the marks can be seen only under an ultraviolet light.They are commonly used in security situations to identify belongings or to prevent the reproduction of unauthorized banknotes.
The same image viewed by white, blue, green, and red lights reveals different hidden numbers. Steganography (/ ˌ s t ɛ ɡ ə ˈ n ɒ ɡ r ə f i / ⓘ STEG-ə-NOG-rə-fee) is the practice of representing information within another message or physical object, in such a manner that the presence of the concealed information would not be evident to an unsuspecting person's examination.
Normally these are invisible to the eye, but become obvious when the document is photocopied. Typically they spell out "void", "copy", "invalid" or some other indicator message. [1] Void pantographs work by exploiting the limitations and features of copying equipment.
The decoder pen, yes-no pen, yes-know pen or magic pen book is a combination of decoder pen or marker specially designed to reveal invisible ink-encoded pictures or writing, [1] in the form of answers to questions or hidden parts of pictures, with specially created children's books with hidden words and pictures. They were most popular in the ...
Hidden text is computer text that is displayed in such a way as to be invisible or unreadable. Hidden text is most commonly achieved by setting the font colour to the same colour as the background, rendering the text invisible unless the user highlights it. Hidden text can serve several purposes.