Re your, "a person's relationship to nature...when a limestone facade
is cleaned",

Actually, Ken, the motivating force wasn't appreciation of nature as
much as being cheap...Why spend a lot of money if it'll just get
dirty again.  In a way this motivation has preserved this particular
building quite well...at least no one there mucked it up.  It was
just left to get dirty, inside and out.

Sometimes (if you're not dealing with real deterioration) benign
neglect preserves historic fabric, when the alternatives may go too
far.  This particular building has travertine walls in the lobby
which is dingy and has dirt clogged pores, but no gunk or cleaning
residue.  Good, honest dirt.  This is relatively easy to extract,
leaving the pores open and textured.

And I agree with you completely, that the best cleaning job is the
one that doesn't go all the way.  It provides the evidence that you
didn't go too far.  As I said once before.  I like to test a cleaning
procedure to failure, then back off.

As to how they would feel about the plight of Monarch
butterflies...these are city folk who wouldn't know a rock dove from
a Shinola.

--Jim