Alvar and butvar: The use of polyvinyl acetal resins for the treatment of the wooden artifacts from Gordion, Turkey

Archaeological excavations conducted by the University of Pennsylvania Museum of Archaeology and Anthropology from 1950 to 1973 at the ancient capital of Gordion in central Anatolia uncovered impressive remains of the material culture of ancient Phrygia. During the early years of the project, the exploration of three massive earthen burial mounds or tumuli in the royal necropolis led to the discovery of one of the most important collections of wooden furniture and objects to emerge from the ancient Near East. Composed of a surprising variety of woods, the artifacts ranged in condition from poor to excellent. Initial attempts to treat the furniture and wooden objects on-site included the application of Alvar, a polyvinyl acetal resin. Soon after, most of the pieces were transferred to the Museum of Anatolian Civilizations in Ankara, where they remained in storage until a rescue program was initiated by the University of Pennsylvania Museum of Archaeology and Anthropology in 1981. Consolidation of the wood with Butvar B-98, a polyvinyl butyral resin, was the procedure adopted after testing to successfully retreat 37 pieces of ancient furniture and more than 50 small wooden objects from the three royal tombs. An assessment of the effects of both resins on the ancient woods is presented here, followed by a description of recent scientific tests conducted on samples of Butvar B-98. These tests include scanning electron microscope studies to determine the extent of penetration of Butvar B-98 into treated samples, hardness testing to assess the strengthening effects of the consolidant on the wood, and exposure to intense environmental conditions to determine the aging characteristics of Butvar B-98 films. The treatment of the Gordion wood has provided a unique opportunity to document and characterize the behavior of two related wood consolidants over a 40-year period. This contribution to the growing body of literature on the subject should assist conservators in making informed decisions when called upon to treat dry archaeological wood.