Hayley Monroe and Ellen Pearlstein
Humidification or conditioning of baskets to effect realignment or re-shaping is a standard conservation treatment performed wherever these collections are held. We know that baskets are particularly prone to damage caused by the alternate swelling and shrinking of fibers due to fluctuations in relative humidity. At the same time, this sensitivity has long been used in the conservator’s favor. The chemical composition of cellulose, specifically its ability to form hydrogen bonds, allows for both water and polar solvents to plasticize dried plant tissue. While humidification (or conditioning when using solvents) has become a standard conservation procedure, its effects on material properties have remained only theoretically evaluated rather than through a material study. In fact, untested concerns have been raised over microbial growth, and also the potential for irreversible swelling of the basketry elements. As a result, polar solvents – for example ethanol – have been added to or become a preferred conditioning media instead water.
The research for this thesis project, conducted at the UCLA/Getty Conservation Program, revolved around designing an experiment to track the extent of swelling and subsequent recovery of basketry samples treated with water and ethanol vapor. These samples represent two plant species, willow (Salix spp.) and spruce root (Picea spp.), one deciduous and the other coniferous, which occur with some frequency in the basketry traditions of the western United States and Canada. The extent of swelling before and after the conditioning process between all the samples was compared, using measurements taken with a Keyence digital microscope. Pure water, pure ethanol, and three mixtures of the two at different proportions, were each evaluated for consequent dimensional changes occurring before, during, and after conditioning to the same relative humidity as is typically used in conservation treatments. The results of this study not only corroborate information from fields as diverse as conservation, forestry science and material science, but also point towards clear trends which can inform the conservator’s decision-making in planning humidification/conditioning treatments of basketry. By performing a material study, we are able to provide clearer guidelines about the effects of different conditioning solutions.