A Study on Common Visualization Methods for Secret Writing done by Invisible Inks and their Sensitivity Over a Period of Time

Abstract

Secret writing is a skill of concealed writing. The art of secret writing is projected to make the written text unreadable by other person who is exposed or deciphered by different revealing process to make the messages readable. Techniques of secret writing are many, but this paper mainly focuses on the use of invisible inks. The current study comprises of secret writing samples which contain hidden messages written using some fruit juices (lemon, apple and grape juice), chemical fluids (detergent, sugar solution and vinegar) and biological fluids (milk, saliva and sweat). They were then visualized using common physical and chemical methods in a specific interval of time; examined from 1 st day to 30 th day after regular interval of five days. Heating and Iodine fuming were found to be the best methods for visualizing invisible inks, among physical and chemical methods, respectively. Both of these methods showed good results up to one month.