FACED WITH THE NEED to releather the Aeolian-Skinner in his home, physicist Harley Piltingsrud mounted a search of all of the scientific literature on leather aging and developed a test to predict the longevity of leather. His test has led to a new standard for organ leather that can be expected to last 40-60 years or more. This 48-page, illustrated booklet shows the determinants of longevity and how to select from commercially available organ leathers, shows how to conduct aging tests of leather, and shows what builders and owners of organs should expect of leather used for covering pneumatic actions, for new organs or for instruments to be restored. The authors summarize the making of leather and how deteriorating upholstery and deteriorating bindings on library books led to early research on leather aging. Published in 1994 by OHS.