Methylene Blue Revisited: The Search for a Trouble-Free Erasure Sensitive Powder

Abstract

It is well recognized that the powdered mixture of methylene blue and starch is highly sensitive for the purpose of detecting physical erasure sites which are virtually undetectable by other methods. Also well known are the problems associated with this method, for example, permanent discoloration of the document upon assimilation of moisture. This paper details the successful search for a formula possessing the sensitivity of the methylene blue/starch mixture minus its disadvantages.

Water analysis

“…A mixture of toner powder and sodium bicarbonate were found to be useful for detecting erasure sites on documents (560). Electrostatic detection of indented images on paper ANALYTICAL CHEMISTRY, VOL.…”