Oh Learned One,

The old glassy square edged tile was glassy and square edged because it was
made from sheets of opaque white glass cut into squares.

The great Willie Lump Lump (or more precisely, his minions) called for that
stuff for the bathrooms in the World Famous Brooklyn Boro Hall Project, and
the Scumbag Weasel Fuck Contractor, Ken's friend and mine, submitted samples,
got them approved, ordered 500 million square feet of it, set it in several
bathrooms, swore that it came out badly because the architect didn't know
what he was doing, and then discovered that if the tiles are cut 90 degrees
in the wrong direction, the ridges on the back of the glass cause it to break
slightly longer or shorter (but never the same size twice), giving you razor
sharp edges and horizontal joints that waver all over the map. If you cut it
with the horizontal joint 90 degrees to the ridges on the back, you get
uniform heights and slight variations in length that nobody would ever see.
All this stuff has subsequently been covered with Carrara marble tiles of
about the same size.

Ralph