In 1904 the director of the Metropolitan Museum of Art complained about "the
disintegrating of the stone of the exterior walls" of the new Fifth Avenue
wing of the Metropolitan Museum of Art (now the main entrance); "Anyone can
see what condition the exterior is in, however, and the necessity of action
of some kind", he said.

He said that he supported the plan of "Professor Doremus" [probably Robert
Ogden Doremus, an analytical chemist teaching at CCNY]  "to coat the
limestone with wax to preserve the stone", a technique frequently mentioned
in the period.

From modern eyes, were wax coatings beneficial, injurious or of no effect?

Christopher Gray