The UV "Black Light" test shows fluorescent whitening making the thread/fabric glow. However this test is inconclusive to determine if an item was made before 1945 as fluorescent whitening agents were in commercial use in 1940. Indeed they had been developed in 1929.
The fluorescent whitening agents have also been used in washing powders, so anything so washed may glow also.
Google Garry Symonds and "The Black Light Test Revisited" for more details.
Keith
__________________
I collect badges and medals of London Transport employees and its predecessor and successor companies, bus, tram, trolleybus, underground railway.
Last edited by popskipa; 19-06-18 at 06:22 PM.
|