On Wednesday, April 7, 1954, several householders and car owners in the Davenport area reported to the newspapers that their property had been spattered with blue spots during a severe rainstorm. A similar incident was reported from Detroit, Michigan on Thursday, April 8, 1954. Newspaper jargon referred to the incident as "blue rain". Varied explanations as to the origin of the "blue rain" included the possibility of wind blown paint, "fall-out" particles from hydrogen bomb tests in the Pacific, vegetable material of some type, tree buds, or pollen. The authors became interested in the problem and a trip was made to one of the houses which had been spattered by the "blue rain". The general appearance was as if the white painted house had been speckled with a fine spray of mulberry juice. The spots averaged 5 millimeters in diameter, the center being a dense mass of bluish-purple material surrounded by a paler halo. An automobile parked on the St. Ambrose College campus presented a similar appearance.
Proceedings of the Iowa Academy of Science
©1955 Iowa Academy of Science, Inc.
Vinje, James M. and Vinje, Mary M.
"A Note on the Origin of "Blue Rain","
Proceedings of the Iowa Academy of Science, 62(1), 92-93.
Available at: https://scholarworks.uni.edu/pias/vol62/iss1/8