BLACK-OUT ENVELOPES
An ingenious method whereby maps and charts may be read on ships and in aeroplanes under virtual black-out conditions has been developed in America. The maps are covered with transparent cellulose-acetate sheeting which contains an orange-red fluorescent pigment. When subjected to ultra-violet “ black ” light from an electric lamp, the pigment becomes sufficiently luminous for the enclosed printing to be "ead. The material in transparent enough for legibility in daylight.
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https://paperspast.natlib.govt.nz/newspapers/ODT19441024.2.80
Bibliographic details
Otago Daily Times, Issue 25674, 24 October 1944, Page 6
Word Count
71BLACK-OUT ENVELOPES Otago Daily Times, Issue 25674, 24 October 1944, Page 6
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