The problem of environmental deterioration of outdoor stonework on buildings is felt worldwide. In addition to moving sculpture indoors and substituting replicas, reducing local automobile traffic, and controlling pollution in cities, artifacts may be coated with protective synthetic films, such as silicones and acrylic or methacrylate polymers. Scientists at the National Bureau of Standards in Washington, D.C. have conducted exhaustive tests to determine the effectiveness of various preservatives available and outline desirable criteria for new materials. As yet no resin tested has met their recommendations, which are that the material should be long lasting, harmless and non-corrosive, should penetrate the stone while hardening but not encrusting the surface, should allow internal moisture to escape while preventing external moisture penetration, and should be easy to apply and maintain without high cost. -- AATA