Dry ice blasting in the conservation of metals: A technical assessment as a conservation technique and practical application in the removal of surface coatings

Cassy Cutulle and Seoyoung Kim


There is a growing necessity within the field of conservation to seek out new methods of cleaning that are safe, effective, and sustainable. The use of dry ice blasting to clean museum objects has been investigated as a potential option in recent years. To continue such research, an experimental methodology was devised to evaluate the risk of abrasion using this method and its efficiency in removing traditional and modern conservation surface coatings from metallic artifacts. Additionally, an assessment of dry ice blasting as a conservation cleaning technique was conducted. Two types of experiments were carried out to measure the performance and efficiency of dry ice cleaning. The first experiment utilized brass, cupronickel, and mild steel metal coupons that were coated, blasted, and assessed under a Hitachi S-3400N scanning electron microscope to evaluate the risk of surface abrasion as a result of dry ice cleaning. The second experiment evaluated the practical efficacy of dry ice blasting in the removal of coatings from historic and modern objects, such as gilded brass furniture mounts and steel musket lock replicas. All experiments were undertaken using the Cold Jet i3 MicroClean dry ice shaving unit. Various coating materials, such as natural and synthetic waxes, petroleum jelly, Paraloid B-72, Paraloid B-48N, Incralac, nitrocellulose lacquer (Ercalene), and shellac were tested in the experiments. The results revealed that the risk of surface abrasion on the metal surfaces using dry ice blasting is minimal at the tested durations and settings used. Effectiveness in coating removal was seen to be variable. Wax-based and petroleum jelly coatings were more effectively removed compared to polymer-based coatings. This project was completed as dissertation research for University College London’s Masters of Science in Conservation for Archaeology and Museums degree program.

This article also presents a case study that focuses on the practical application of dry ice blasting for the cleaning of mail (often known as chain mail) on the Oriental helmets at the Wallace Collection in Central London. The mail on the helmets had previously been coated with petroleum jelly, which interacted with the metal over time, resulting in discolored, tacky, and greasy mail. Dry ice blasting was employed to remove the aged surface coatings on the mail as an alternative technique to conventional chemical cleaning methods. The detailed process of the project, with an evaluation of its effectiveness and the practical limitations, is outlined.

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2015 | Miami | Volume 22