AIC's 52nd Annual Meeting

In the fall of 2022, the National Park Service Harpers Ferry Center (HFC) embarked on a year-long project aimed at understanding the conservation practices and materials used to care for outdoor iron cannons, thanks to a generous grant from the Samuel H. Kress Foundation (administered by the Foundation for Advancement in Conservation and the Gettysburg Foundation). Outdoor cannons and artillery are subject to humidity and temperature extremes, airborne abrasives, pests, ultraviolet radiation, and prolonged moisture from weather-related events. Routine exposure to these conditions can cause premature failure of protective coatings and paint systems, leading to rust and eventual deterioration of the metal structure. As a result, the public display and interpretation of the historic cannons can appear as general disrepair and neglect. Current procedures for treating these objects involve clearing the surface of corrosion and the removal of previous coating systems, followed by the application of a new protective primer and top-coat system. Cannon coatings have traditionally been paints, but over the past few decades new materials have been introduced, including: epoxies, polyurethanes, water-based emulsions, and other materials that offer a more durable, longer-lasting coating system that can be applied safely and more efficiently.

The basic procedure for coating outdoor cannons and artillery is relatively straightforward and understood by conservators and caretakers alike. However, the complexity lies within the selection and application of an optimal coating system deemed appropriate for an individual cannon. This selection is primarily informed by specific condition issues observed, previous treatment campaigns, the cannon’s geographic location and immediate environment, and consideration of the personnel available and responsible for coating procedures.

This research project focused on compiling and interpreting data to create a comprehensive resource that delineates specific materials, equipment, procedures, and considerations for the treatment and cyclic maintenance of outdoor iron cannons. By surveying the condition of 192 cast iron cannons on display around Gettysburg National Military Park memorial field, interviewing and receiving treatment case studies of past NPS projects, and performing the application of several treatment materials, a final “Resource for Understanding Conservation Coatings for Outdoor Iron Cannons” was produced that can be utilized by conservators and collections caretakers alike in planning and supervising coating treatment campaigns.