Stasi / Facebook / Big Data DAAD Day 24 – Automation in Stasi postal surveillance: Opening letters with sensitive materials using cold steam


Credit: BStU

Since hot steam could damage sensitive contents like photographs, the Stasi used the C-83 (“Cellophan 83”) “cold steam” generating device to open those letters. Produced in Hungary, the C-83 used a special film (cellophane) stretched over a tray filled with distilled water. Up to 25 letters could be placed on the film, flaps down, so that when the water in the tray was heated to 50ºC the “cold steam” diffused through the film and dissolved the glue on the envelope flaps.

The procedure was time-consuming because cold steam dissolved the glue at a much slower rate than the hot steam method. Once the glue started to soften, workers had could only lift the letters off the foil for a short time in order to carefully open them using a special spatula.


Credit: BStU

It is unclear if this is an original mass-produced device or is a product modified by the Stasi OTS. It is constructed of painted sheet metal, cast plastic, and other materials that suggest it was primarily constructed in a factory, though it is possible the Stasi made modifications to assist in letter-opening.


Credit: Museum in der Runde Ecke


Credit: Museum in der Runde Ecke


Credit: Museum in der Runde Ecke

  1. Kaltdampf-Öffnungsgerät zum öffnen von Briefen (Zellofanbodengerät) (Inventory no. 00006). Objekt- und Fotodatenbank Online im Museum in der Runden Ecke. Accessed June 13, 2017.
  2. BStU. Die Stasi und das Postgeheimnis. Accessed June 10, 2017.

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