The Acid that Causes Blue Stains

Great excitement was caused by a strange occurrence in a Protestant church at Wiesenfeld, Lower Bavaria, 

Germany, in the spring and summer of 1977. The congregation had renovated the deteriorating church at great expense during the previous year, but now they faced a disaster. Huge blue stains were found to have formed in all parts of the plastered inte- 

21 Un expert evoque la presence de gaz mortel dans la grotte , Le Quotidien de la Reunion, June 25, 1998. 

A few weeks after the replastering of the church with a water-resistant cement mortar, the entire church had been fumigated with Zyklon B (hydrogen cyanide) to exterminate woodworm in the choir stalls. The hydrogen cyanide, released by the Zyklon B, did not just kill woodworm it 

Reports of blue pigmentation of walls resulting from fumigation with hydrogen cyanide for the destruction of vermin in areas with 

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