Woman comes in to collect her glasses. Picks them up. “Are these glass or plastic” “they are plastic” “what? I wanted glass” “ohh umm, (I look at the order) yeah plastic, im 99% sure that lens is not actually made in glass” “yes it is” “oh?” “so are these cheep plastic” “there not cheep plastic they are CR39 witch is a plastic polymer manufactured to the highest optical quality possible for that lens form” (yeah I was trying to lay it on thick) “so are they plastic or glass?” “the lenses are made of a type of plastic” “I wanted glass, I showed the man here before my old glasses and I said I wanted the same” “well that type of lens I don’t think is made in glass anymore and probably hasn’t for a very long time” “well I got these 1 year ago and they are glass” (she takes them out of her bag and hands them to me and I examine them) “they are plastic” “what?” “These are cr39 as well.” “How do you know?” “Well 1. They don’t weigh what a glass lens would. 2 when you tap the lenses they don’t make the sound a glass lens would, 3 they are not cold like glass would be and 4 the lens type isn’t made in glass” “so are they glass or plastic, coz I showed the man these and said I wanted the same” “well good news then coz the are the same” “glass?” “No”