It is first necessary to determine the transmission of UV radiation through the refer-
ence plate. Prepare a 100% transmission reference sample by spreading a few mi-
croliters of glycerine or another appropriate UV-transparent substance on the rough-
ened side of a substrate plate. The dose of glycerine used should be such that the
entire surface is completely covered, but with no excess (approximately 15l for a 50
x 50mm plate).