Invisible Ink Detection on Questioned Documents
Secret or invisible inks have been known to have a history dating back to the development of ink supplied writing instruments. Espionage, industry sabotage, prison communications and aged/weathered handwriting are examples of cases that may involve the detection and decipherment of invisible inks. Although not always successful in all cases, the use of oblique lighting and UV, IR and natural lighting methods along with digital imaging, most attempts are to some degree successful.