1 INTRODUCTION

Paper can be used to create support structures to house a wide variety of works of art and artifacts. Albums, window mats, and folders have protected works of art on paper for many years. When proper designs and adhesives are employed, paper can be used to support solid or nonplanar works. The available range of weights, textures, and chemical compositions increases the utility of paper in the creation of housings that provide steady, inert, nonconstrictive support. Papers can be bonded with many different types of adhesives to accommodate the chemical requirements of the work.

Conservation-quality papers are made of cotton and cotton linters, linen, abaca, alpha cellulose from purified wood pulp, and bark-derived fiber such as kozo, gampi, or mitzumata. These fibers differ in strength, absorbency, and texture, but in their lignin-free forms they provide a simple material that has been shown to be inert over long periods. Chemical buffers such as calcium carbonate enhance the longevity of a paper and interact with acids. Scavengers such as active carbon and zeolites built into papers and boards will adsorb a wide range of harmful substances. Adhesives can complicate the task of creating a housing in which all the components are simple and well known. Some boards are not laminated, and thus they have no adhesive layers. Those that do have laminate layers should be evaluated carefully. A board that has no calcium carbonate would not be able to protect against a PVA laminating adhesive that has not been properly handled and could off-gas acid. Some of the best-known adhesives, such as starches and modified starches (dextrins), are polysaccharides, as celluloses are. These adhesives can be used in settings in which chemical simplicity is sought. Unfortunately, starch, like methyl cellulose, has a low tack and cannot be used when significant strength is required. Synthetic adhesives can provide greater bonding strength, but PVA and EVA emulsions and thermoplastics may off-gas and should be isolated from the housed object by an alkaline layer. Thermoplastic polypropylene and polyethylene or nylon adhesives that require an industrial, high-temperature gun present a less volatile adhesive choice, but they cannot be used in all cases due to their thermal activation mode. If artist's acrylic gloss medium is painted on two layers that are to be bonded and allowed to dry, it can be used as a thermoplastic when heat is applied to the two layers.

An object that may contain highly reactive constituents such as proteins can be housed in an enclosure made of a simple lignin-free cellulose without an alkaline buffer. The components of the enclosure are joined with starch or an appropriate thermoplastic adhesive. Objects made of materials that may themselves off-gas, such as celluloid or wood laminates, could be housed in a structure made of paper or board that can scavenge those pollutants. When the object requires isolation from an unstable or deleterious environment, a barrier layer such as a plastic and metal foil laminate or plastic impregnated with a metallic sacrificial scavenger can be placed outside the primary support structure. The barrier may be used or not, as conditions dictate.