Decipherment of Disappeared Ink: A Case Study

The disappeared or invisible inks are fluids used to for secret writing. These types of inks are revealed by heat, chemical reaction and UV light. Disappearing inks are acid base indicators showing different colours at different pH. Writing with this type of ink disappears after about 65 h. These inks could be used for forging the documents such as agreements, cheques, property documents and other important documents. Many destructive and nondestructive methods are available for forensic decipherment of these disappeared writing. In present communication, a simple nondestructive method is applied for decipherment of disappeared signatures on share transfer agreement and other related documents.


Introduction
Basically, ink is a composition of dyes or pigments along with some additives to give desired physical properties. Nowadays, varieties of ink composition are available in the market which consists of various organic, inorganic and synthetic material with various characteristics and properties 1,2 . Disappearing ink is used as marking system for sports, in dress making industry. It is also used as teaching material to make answer invisible. By using coloring agents, answers become visible. Disappearing inks are also applied in paint industries to locate the area which is not painted.
However, these are a great challenge for forensic document examiner as used in forgery or counterfeiting documents.
The alteration is one of the most common types of fraudulent observed in the examination of questioned documents. It includes addition, subtraction, and obliteration and to alter any security features on the documents. There are two methods used for examination of questioned documents namely non-destructive and destructive. A non-destructive method involves use of magnifying lenses, electronic In present communication a non distructive method for decipherment of disappeared ink writing is illustrated. The aim of the present work is to decipher the vanished inks and to find out whether the writing could be deciphered with exposure to different light sources, alkaline solution, vapour, or thermal effect and to make these results demonstrable in the court.

Case history
A complaint was lodged at police station about disappearance of signatures made by transferor on share transfer agreement, share transfer form and on the list of shares.
All the documents were submitted in the forensic laboratory for examination.

Microscopic and optical methods
All disappeared signature sites of documents were examined under stereo microscope of Leica make (magnification 20X-40X) with direct light and oblique light.
Further these sites were observed under UV and spot light of VSC5000 manufactured by Froster and Freeman Ltd.

Chemical Methods
The signature sites were sprayed by dilute sodium hydroxide /dilute ammonia solutions. All chemicals used were of analytical grade and distilled water was used for preparation of solutions. The signature sites were exposed to iodine vapours in standard vapour chamber. Reappeared signatures were photographed using digital camera.   The carbon dioxide present in air reacts with sodium hydroxide to form sodium carbonate, which is less basic than sodium hydroxide. The resulting sodium carbonate change the blue color to colorless, the alcohol evaporates and left the colorless residues of ink on documents. Due to said neutralization, pH changes and makes indicator colourless, hence ink disappears. When this exposed to iodine vapours iodine adsorbed on the surface of sodium carbonate and writing appears in.

Results and discussion
After removal of document from chamber iodine sublimes then brownish color slowly disappears.

Conclusion
The spraying of aqueous sodium hydroxide and ammonia solution is effective method for deciphering of disappeared inks. However, it may harm the important document. For decipherment of disappeared ink writing on important document exposure to iodine vapours is effective method. This method is nondestructive method. In this study, we propose the effective method for deciphering of disappeared inks.