Not just lemon juice

Two Michigan State University researchers have unlocked the secret invisible-ink formula used by the former East Germany secret police, the Stasi:

The Stasi’s technique of transferring top-secret messages worked like a piece of carbon paper. An agent would place a piece of paper impregnated with the chemical cerium oxalate between two pieces of plain paper. As the agent pressed down to write, the chemical was transferred to the piece of paper beneath.

The person on the receiving end of the message then developed the note with a solution of manganese sulfate, hydrogen peroxide and other chemicals. The process activated the cerium oxalate to reveal the hidden text. A successful reaction yielded orange writing.

Permanent link to this article:

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Easy AdSense Pro by Unreal