Heat- and Solvent-Set Repair Tissues

ABSTRACT For decades, precoated heat- and solvent-set tissues have been the preferred method for mending certain types of library and archival materials due to their translucency and ability to be used without introducing moisture. In recent years, the adhesives long used to make these tissues became unavailable. The National Archives and Records Administration and the Library of Congress report joint testing of a variety of precoated tissues made with Lascaux 498 HV, Lascaux 303 HV, Avanse MV-100, Plextol B500, Aquazol 200, and Aquazol 500, adding to and building upon their research presented in 2015. Prepared tissues were applied to substrates using both heat- and solvent-set methods, then they underwent a variety of analytical testing. Testing assessed color change and reversibility after artificial aging, blocking of mends and fills after natural aging under pressure, and the adhesives’ interactions with silver-based photographic materials. The method of application – heat or solvent – did not affect aging or testing results. The Avanse/Plextol tissues failed the color change tests. The Aquazol 200 and 500 dilutions and several Lascaux 498 HV and Lascaux 303 HV dilutions passed testing. Six successfully tested mixtures are presented, with case studies of use and recommendations for ongoing quality assurance.