Secret Writing

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Description

For 95 years, a small number of documents related to invisible ink were national security-classified material and unavailable to the public. Believed to have been the oldest documents still classified by the United States, they detail German secret ink formulas developed during World War I. They were approved for release in the year 2011. This document describes the method and ingredients for using invisible ink.

Citation

This primary source comes from the Records of the Office of the Chief of Naval Operations.

National Archives Identifier: 5890791

Full Citation: Secret Writing; File 20961:174; Confidential Suspect and General Correspondence Files, 1913 – 1924; Records of the Office of the Chief of Naval Operations, Record Group 38; National Archives Building, Washington, DC. [Online Version, https://docsteach.org/document/secret-writing/, April 2, 2026]

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