Not quoting the VERY long message...
I suspect that whomever said "using 78's as archival media" (not in
those exact words) was thinking of using "shellac" discs as a storage
medium, given their apparent resistance to age-related deterioration
(on which I earlier commented...)!
In that case, the limiting characteristic would be the particle size
of the material used as a binder. If one attempted to make a workable
digital recording using the standard shellac-based compound, that
wouldn't work! We know that the size of the binder particles is such
that the particles produce an audible "78 hiss" using playback methods
whose signal is created by the point of a stylus (needle) following
undulations of a groove. Since the record makes one rotation in 1/78
of a minute (about .769 seconds), and travels, during that period, a
distance between a maximum of c. 10*pi (31.416) inches and a minimum
of c.3-3/4*pi (11.78) inches...or between 40.84 ips and 15.3 ips.
If we assume a "centre frequency" of 6KHz for "shellac hiss" (I don't
think this number has been established...) we get a binder-particle
size ranging from .002552 inches to .00681 inches (give or take).
Compare that to the average size of a CD "pit" (let alone DVD's!)
and what we see is a "landscape" which looks rather like the
Rocky Mountains when magnified enough to make digital "pits"
Steven C. Barr