Carnival Glass - Six Tumblers Worth More?

Early "carnival" glass (1908-1930) is said to be distinguishable from new
(1960's- ) by turning it over. The old is without iridescence underneath,
i.e. the true color of the underlying glass can be seen under the base. New
carnival is iridescent all-over. This is said to be because the old method
was spraying on the chemical "dope" while the pieces crept down a conveyor
belt through an annealing lehr, while the new glass was covered all-over by
the dope, possibly by dipping. The point is that the early iridescent -
especially the marigold - was cheap mass-production ware and not much care
was given to getting a thick and uniform metallic coating, while the new
iridescent ware was usually of a better quality because its audience was
glass collectors who were only looking at the exotic color and fine finish.
[Maybe some real carnival collectors with a background in chemistry could
give us both some clues about whether the metallic coating might sometimes
have bonding problems or a tendency to decompose.] - Bob

Janice Hudnall...

This just isn't entirely true. Probably 50 % of our glass is irridized on
both sides (and we don't have anything later than @ 1930. Admittedly the
finish is not as heavy, but its there.) And yes, it was mass produced, but
in most cases it was well made . Compare the things that were turned out of
1910 factorys as opposed to today. The metallic coatings were baked into
the glass, and should be fairly indestructable unless abraided. The
difference in finish I have heard attributed to the factory worker that was
doing the application of 'dope'. In my opinion, it's the new stuff that's
nasty :).