Coming in from the Cold: Considerations for Equipment Selection, Operation, and the Development of Cleaning Parameters for Dry-Ice Blasting

William Hoffman

William Hoffman Conservation Project Manager & Senior Conservator, USS Monitor Project, The Mariners' Museum, VA

Abstract

In the spring of 2013, conservators within The Batten Conservation Complex (BCC) at The Mariners’ Museum and Park (TMMP) in Newport News, Virginia began looking into the application of dry-ice cleaning for the removal of corrosion on wrought iron artifacts recovered from the wreck site of the Civil War Ironclad USS Monitor. Although the technology had been used in industry for several decades and had started to be researched within the conservation field, detailed information was limited on the types of dry-ice blasting equipment available as well as the operating requirements and limitations of the machinery. Furthermore, research on blasting technique and a developed procedure to identify safe cleaning parameters was also unavailable. Therefore, conservators at the BCC experimented with several blasting units and compressor systems along with investigating different blasting nozzles and various forms of carbon dioxide (CO2) media. The results of this experimentation enabled the conservation staff to gain a better understating of the dry-ice blasting process and design a blasting system adequate for its needs. Once, the blasting equipment was identified, a sample testing procedure was developed to determine safe clean parameters using a custom-made testing apparatus coupled with before and after cleaning photographs of sample material using a HYROX microscope. Successful cleaning test results for corrosion removal on wrought iron led TMMP to seek grant funding to purchase a blasting system. Since April of 2016, dry-ice blasting has been regularly employed within the BCC with additional research being conducted to develop effective cleaning parameters for cast iron and copper alloys.

This presentation will provide an overview of the dry-ice blasting process and give insight into some of the considerations that need to be made when selecting and operating dry-ice blasting equipment. Additionally, a description of the method developed to identify safe cleaning parameters will also be given.
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Author Biography

William Hoffman, Conservation Project Manager & Senior Conservator, USS Monitor Project, The Mariners' Museum, VA

Will Hoffman received Bachelor’s degrees in Anthropology (concentrating in North American and Historic Archaeology) and Fine Arts (concentrating in sculpture and metal casting) from The State University of New York College at Buffalo. In addition, he holds a Master's degree in Art Conservation specializing in the conservation of objects from Queen's University in Kingston, Ontario. He has worked at Mariners’ Museum since 2009 focusing on the conservation of archaeological metals recovered from the wreck site of the USS Monitor. During his tenure at the museum, his research interests have encompassed the evaluation of cleaning and stabilization methods for archaeological iron materials as well as the study of 19th century metal casting and steam engine technologies. Presently, he manages and coordinates of all conservation-related activities within the Batten Conservation Complex and The USS Monitor Center.