![]() Faded blue and black Frixion ink pen strokes could be deciphered clearly under ultraviolet lighting and most preset excitation wavelengths of infrared luminescence while only four wavelength bands of infrared luminescence could be used for the faded red Frixion ink. Results showed that the colour of Frixion ink faded completely under both heat and friction from an eraser but the indentation of pen strokes were still observable by treating the samples using Electrostatic Detection Apparatus and the Video Spectral Comparator 6000. ![]() Black, blue and red Frixion inks were deposited on foolscap paper and the pen strokes were allowed to fade away through heat or erasure before new entries were overwritten onto the same spot using the same colour of pen. The first part of this experiment focuses on deciphering of faded Frixion ink pen strokes while the second part is aimed at differentiating between the faded and fresh Frixion ink without affecting the original state of the documents. Although such alteration cases have not been reported in Malaysia yet, suitable methods ought to be developed so that local document examiners are prepared beforehand for such situations. Hence there is potential that Frixion ink could be misused repeatedly on the same document for fraudulent purposes. Therefore, NH3 had to be sprayed for 0.16 g/50 mL with negligible harm.įrixion ink, which has been introduced into Malaysia's market in recent years, has a special characteristic that it can fade under heat or be rubbed off. ![]() To decipher the entries that disappeared, an instrumental method (Video Spectral Comparator‐8000) and a chemical method (using NH3 vapor) were used, succeeded at 0.32 g/65 mL, but failed at 0.16 g/50 mL thymolphthalein. After 40 h, ink residues were not visible on promissory notes written with the ink with the optimum pH (pH = 14) value. Fountain pens were filled with the abovementioned ink solutions and applied to promissory notes for experimental purposes. Among the prepared solutions, 0.16 g/50 mL and 0.32 g/65 mL thymolphthalein at pH 14 were the optimum solutions that were not distinguishable from regular ink when applied to promissory note. A total of 54 different solutions containing thymolphthalein were prepared at six different concentrations and nine different pH values. In this study, thymolphthalein indicator solution was prepared as a disappearing ink. Washington encouraged his agents to write their invisible messages in the blank spaces of common books to make them less suspicious.Disappearing inks can be used for forgeries in many fields. The first chemical was used to write the message, and the second chemical, when applied to the first, created a reaction that revealed the message. James Jay, a doctor and brother of American congressman John Jay, created an invisible ink system that used two chemicals. He wanted an ink that could not be revealed using heat, making it harder to expose. George Washington took the use of invisible ink a step further. British intelligence officer Major John André instructed his agents to write an “F” for flame or an “A” for acid in the corner of a paper to indicate which should be used to expose a message. The first was made visible when exposed to heat, and the second was made visible when exposed to an acid. The British used two different types of invisible ink. How was invisible ink used by Washington?ĭuring the American Revolution, invisible ink was an important method of communication for spies on both sides.
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