See the Parks Canada Glass Glossary, page 12, for the use of short wave UV
light to help to identify lead glass (it fluoresces ice blue).  In my
experience it is not "old lead glass" that shines yellow under the light
but soda lime glass.  As for using the light to differentiate between hard
and soft paste porcelain, it is GENERALLY but NOT ALWAYS the case that hard
paste fluoresces a deep purple while soft paste simply reflects the light.
This is, as was pointed out just now by an esteemed co-worker,
archaeological folk wisdom without, as far as I know, scientific proof.
Does anybody have scientific proof of these observations?

Meta Janowitz