Barcol hardness test the Barcol impressor was developed by Walter Colman as a hand-held, portable means of assessing the hardness of a material during World War II. The United States Army Air Corps required a hand-held method of checking the hardness of rivets due to concerns that aircraft could be sabotaged by replacing normal rivets with soft lead or wooden ones which would fail during flight. The impressor operates when the tip is pressed against the material in question. The hardness of the material determines how far the tip indents and this is transferred by a tension spring and lever to be read
Walter Janka judgement against him. At the same time a legal and journalistic displute flared between Janka and Wolfgang Harich about the details of those 1957 show trials. Janka's contribution to dramaturgy received recognition in the form of the Heinrich Greif Prize in 1990. On 16 December 1989 Janka was a member of the presidium at the of the SED (then in the process of transforming itself into the PDS / Party of Democratic Socialism / " Partei des Demokratischen Sozialismus") held in Berlin at the Dynamo Sports Hall. In 1990 he was a member of the "Council of Elders" of the