Aerogels can be made out of many different substances, including silicon dioxide (also called silica), carbon and even egg albumen, though silica aerogels are among the most common.
The two great moments in this installation are a room containing mammoth albumen prints of Yosemite and other landscapes, and in another room, a giant panorama of San Francisco.
The last gallery has a pair of albumen prints by Gardner from May 1865 one of a triumphant parade led by horse-mounted soldiers along a Washington avenue, the other of a grandstand of spectators that point toward the future of photography.