For the museum-wide “Gyroscope” exhibition, the Hirshhorn Museum and Sculpture Garden has arranged its permanent collection thematically. One room examines color—or rather the lack of it—in modern painting, displaying black-and-white works by such artists as Ad Reinhardt, Frank Stella, and Franz Kline. Another room details the conundrums that art conservators face every day: Should we keep the original film placed over this 1958 collage, even though it’s yellowing? What kind of patina should this Henry Moore sculpture have? How do you keep sculpted wax from melting? And why did the blue ink in this Picasso sketch simply disappear? Once you’ve mulled these puzzlers, be sure to check out Ann Hamilton’s crowd-pleasing 2001 installation at hand, in which automated machines, with a pffft and a crinkle, drop pieces of onion-skin paper onto the ground at random intervals. A docent-led tour offers “Gyroscope” highlights at 7 p.m. (see City List for other dates) at the Hirshhorn Museum and Sculpture Garden, 7th Street and Independence Avenue SW. Free. (202) 357-2700. (Louis Jacobson)