AIC 53rd Annual Meeting

Thousands of visitors to Valley Forge National Historical Park in Eastern Pennsylvania have passed by “the forge” while walking the Park’s many trails. The forge was constructed in 1742 to finish crude iron “pigs” into hardware and tools. However, in 1777, British forces burned the valley and the forge—a major strategic site—to the ground. The Pennsylvania State Park Service excavated the Upper Forge Site ruins in 1929-1930 before the Park’s transition to federal ownership. Until recently, over three hundred wooden fragments of the forge’s structure sat in a barn. The artifacts fluoresced bright green under UV and reeked of mothballs—a telltale sign of the petrochemical creosote. The condition of the collection lent itself to a major collaborative research project including the Valley Forge National Park and Harpers Ferry Center in West Virginia.

    Before treatment began, we established a triage lab in an open barn to temporarily store the collection. This process required the cooperation of Valley Forge’s maintenance staff and Harpers Ferry Center in order to provide the necessary infrastructure and resources. Our greatest priority was to remove the creosote coating, thus allowing the collection to be relocated to a climate controlled environment. Creosote is composed of strong volatile organic carbons (VOCs), which can cause respiratory irritation and damage. Unfortunately, creosote removal scholarship provided little help in devising a treatment plan for the Upper Forge Site. While creosote can be removed on an industrial level using abrasives or water pressure, these methods were not suited to fragile archeological material. The treatment plan had to be designed and tested from the ground up.

    The condition of the collection was suitable for comprehensive testing. Boxes of dissociated debris were available for spot-testing. The wood’s internal cell walls and structure had long since been destroyed by the outside environment. Fluctuations in temperature and humidity caused the objects to expand, contract, and severely split in the barn. Conservators do not typically recommend submersion baths for archaeological wood for fear of bursting cell walls with fluid. However, the Park was more comfortable with pursuing wet treatment because the collection had already undergone this damage during storage. 

    After I conducted analytical testing at the Harpers Ferry Lab, I employed triage-style processing at the Park. I treated the wooden artifacts using a combination of solution, mechanical, and poultice cleaning. The creosote removal also yielded new residue-limiting poulticing techniques. I encountered challenges during the numbering process, which required the insight of conservators across multiple states. The project concluded with a modular storage method, also designed by a committee. 

    The Upper Forge Site project was an experiment in collaboration. Craftsmen, curators, preservationists, conservators, and analytical scientists across the federal government provided their expertise to the protection of this historically significant collection. Within a year, we had relocated the forge fragments from a barn to a climate controlled archive. Historical research has been compiled for the eventually interpretation, exhibiting, and possibly even reconstruction of the revolutionary forge.