Acne gel for green ear syndrome? A study on copper corrosion stain removal from poly(vinyl chloride)

Dawn MP Wallace, Aaron N. Shugar, Jonathan Thornton, and Rebecca Ploeger

Abstract

The removal of copper corrosion stains from plasticized poly(vinyl chloride) are of concern to both conservators and the collectors of popular vinyl dolls. Early Barbie dolls in the 1960s and 1970s were sold with earrings inserted into the ear, and Dawn dolls sold in the early 1970s featured bendable knees with internal metal and dense plastic armatures. These components are comprised of copper alloys which over time may create corrosion stains on and within the plastic. The conservation field is still relatively hesitant to implement invasive treatment of plastics, while public collectors are actively trying treatment methods to reduce the staining. Currently the most common method used by collectors employs common over-the-counter acne topical gels.

Two acne topical gels were tested using methods described by private collectors to determine the effectiveness and any potential irreversible damages caused by these removal methods of the corrosion staining. Neutrogena gel contains salicylic acid as the primary acting compound and the other by Clearsil contains benzoyl peroxide. Normal and fluorescence induced illumination documented the visible change of the samples during testing. The samples were weighed to determine possible loss of plasticizer or material. X-ray fluorescence spectroscopy was employed to follow movement of the stain by presence of the copper αβ K-lines. It was determined the salicylic acid gel removed copper from the sample while the benzoyl peroxide acted primarily as a bleaching agent. Pyrolysis-gas chromatography-mass spectroscopy was also used to characterize the poly(vinyl chloride) samples, gels and removed residues to determine the materials extracted during the tests.