Pine pitch: New treatment protocols for a brittle and crumbly conservation problem

Nancy Odegaard, Marilen Pool, Christina Bisulca, Brunella Santarelli, Madeleine Neiman and Gina Watkinson

Abstract

In 2011, the Arizona State Museum was awarded a Save America’s Treasures grant to carry out a conservation survey of more than 22,000 basketry objects, including over 4000 ethnological baskets. This survey identified around 100 pitch-coated baskets, and a significant number were found to be in extremely unstable condition. Severe oxidization of the pitch had resulted in cracked, crizzled, brittle, and crumbly surfaces. To prevent further damage, the baskets were triaged; those considered at imminent risk for loss were treated mid-survey using solvent reactivation. This interventive conservation treatment stabilized the remaining pitch surfaces, allowing the baskets to be safely moved to their new storage locations. It also enabled future analysis and the research of the materials and technology used to fabricate these unique baskets.

This project illustrates the value of combining survey, analysis, and treatment activities. It initiated a more in-depth analysis of the pitch used in Southwest Native basketry. Pitch samples from over 70 baskets were analyzed with Fourier transform infrared spectroscopy (FTIR). These results were compared to fresh pine resin heated to simulate traditional pitch processing. Differences in appearance among the pitch surfaces appeared to correspond to different processing regimes. FTIR analysis also confirmed that this conservation treatment did not alter the chemical integrity of the pitch coating.

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