Hello All,

I have a question on visual identification of, and differentiation among
shellac, instantaneous and vinyl grooved disks. Are there quick visual and
non-destructive methods of determining the type of disk?

I am aware that most instantaneous have three "spindle" holes in the center,
and one can generally determine that a disk is an instantaneous based on the
core material (if one can see the core material.) Any other suggested
methods of quick ID and differentiation - barring cracking the edge of the
disk to see the material composition? Is gently tapping the disk surface,
and listening for aural cues about material density an useful practice?

Thanks for your assistance!

Best,
Tracy Popp
UIUC Graduate Student MLS