The note mentioning "spit" as a universal cleaning fluid reminded me of
my years as a curatorial technician in an invertebrate zoology department,
where "nose oil" was the preferred treatment for a shell that was too
slick to accept India ink.  Wipe a finger against the side of the nose,
then on the shell (or wipe the shell against the side of the nose), then
write the catalog number on the resulting smear with a crow-quill steel
pen and India ink.  It never occured to me to wonder whether that was
really good for seashells.
 
On the "up" side, I do remember hearing that the preferred chemical for
removing verdigris from bronze objects was ... peaches.
 
       +------------------------------+------------------------+
       |  Barbara Weitbrecht          |  [log in to unmask]  |
       |  National Air & Space Museum |  [log in to unmask]       |
       |  Smithsonian Institution     |  (202) 357-4162        |
       +------------------------------+------------------------+