1 INTRODUCTION

The National Museum of the American Indian (NMAI) is in the process of moving approximately 168,000 ethnographic objects and 632,000 archaeo-logical artifacts from outdated facilities in New York City (the Research Branch) to new facilities near Washington, D.C. (the Cultural Resources Center). An integral step in this move is to carry out a preventive pest management protocol to minimize the possible transfer of live insect pests within the collections to the new facility. For much of the collection, the preventive method is to treat objects with low temperature prior to relocating. Included in the vast number of objects treated are certain “borderline” types of materials for which low temperature was feared to be detrimental in theory, but to which experience and anecdotal evidence showed no damage.

Low-temperature (in the range of –20�C to –30�C) pest eradication in conjunction with an integrated pest management system has been the preferred method for museum pest control since the mid-1980s (Jessup and Ballard 1997; Strang 1997), in part as a reaction to federally mandated legislation limiting the use of pesticides. Subsequent development of both anoxic environments and the use of thermal methods has produced important applications in museum pest control. However, the ease, nontoxicity, speed, cost effectiveness, and definitive kill provided by low-temperature pest control continue to make it the favored pest control process whenever possible.

The existing conservation literature emphasizes the aspects of proper temperature, freeze duration, insect resistance, condensation, and practical low-temperature procedures. Little has been published about damage to artifact materials, although several references give lists of materials that are not recommended for this treatment (Florian 1986b for lists and procedures; Berkouwer 1994; Raphael 1994; Michalski 1996; Strang 1997; Baughman 1999). The types of potential damage feared include cracking, delaminating, fatty bloom, staining, corrosion, and fungal growth. Some NMAI objects considered vulnerable to low temperatures are not treated in the freezer but instead are managed with Vikane (sulfuryl fluoride), anoxic treatments, or careful inspection and isolation. The expense and time required for these alternatives, however, make low temperature the preferred option for the thousands of objects involved in the NMAI project. Some potentially vulnerable objects are being frozen at NMAI because they are part of a composite object where the risk of infestation seems greater than the risk of damage or because the object shows evidence of prior infestation.

Within the limitations of the move process, an observational study was undertaken to test the hypothesis that these materials are not damaged by low-temperature pest control. Four categories were investigated: materials in composite objects, cracked objects, lamellar objects, and waxy or oily objects. The results of this study, together with information about the mechanisms of damage due to low temperature and the characteristics of artifact materials at low temperature, contribute to an informed approach for the treatment of potentially vulnerable materials.