Prepared Disappearing Ink and Deciphering of Documents

Area of Science:

• Forensic Science
• Analytical Chemistry

Background:

• Disappearing inks pose a risk for document forgery across various sectors.
• Thymolphthalein, a pH indicator, was investigated for its potential as a disappearing ink.

Purpose of the Study:

• To develop and optimize a thymolphthalein-based disappearing ink.
• To assess the detectability and recoverability of the ink on documents.

Main Methods:

• Prepared 54 thymolphthalein solutions across six concentrations and nine pH levels.
• Applied optimized ink formulations to promissory notes using fountain pens.
• Evaluated ink disappearance and recovery using instrumental (Video Spectral Comparator-8000) and chemical (ammonia vapor) methods.

Main Results:

• Optimal ink formulations (0.16 g/50 mL and 0.32 g/65 mL at pH 14) were indistinguishable from regular ink on promissory notes.
• Ink residues were not visible after 40 hours for the pH 14 formulations.
• The 0.32 g/65 mL formulation was successfully deciphered using both instrumental and chemical methods; the 0.16 g/50 mL formulation required ammonia vapor treatment.

Conclusions:

• Thymolphthalein at pH 14 can be effectively used as a disappearing ink for document alteration.
• Recovery of the altered information is possible using specific instrumental and chemical techniques, with varying efficacy based on ink concentration.