Library of Congress heat-set tissue is a material especially designed for dry mending of tears and lacunae in semi-rare book papers. It is an alternative method to traditional aqueous mending techniques and is economical when very large numbers of tears need to be repaired. The tissue is coated on one side and should never be prepared by any method of impregnation. The materials required are Rhoplex AC-73 Acrylic resin, Plextol B-500 acrylic resin, distilled water, glass sheets or uncoated 2 ml polyester film and lens tissue preferably from J. Barcham Green, England. Equipment needed are beakers and container, 1 - 2 quarts, and a soft 5 inch Japanese brush or airless spray equipment capable of critical judgement. The procedures for preparation and application are described in detail and a manufacturer/supplier list is included.