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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.
[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.
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 ...
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.
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.
Iron gall ink (also known as common ink, standard ink, oak gall ink or iron gall nut ink) is a purple-black or brown-black ink made from iron salts and tannic acids from vegetable sources. It was the standard ink formulation used in Europe for the 1400-year period between the 5th and 19th centuries, remained in widespread use well into the 20th ...
Immigration advocacy groups and Democratic leaders are seeking to disrupt President-elect Donald Trump's plan to deport millions of undocumented immigrants by pre-drafting lawsuits that could be ...
Scantegrity II ballot and decoder pen. Left: Unmarked optical scan bubble. Right: Marked optical scan bubble revealing confirmation code "FY" The Scantegrity II voting procedure is similar to that of a traditional optical scan voting system, except that each voting response location contains a random confirmation code printed in invisible ink. [4]