Cross-section Analysis: Original Use of a Proteinaceous Coating?

Additional SEM-EDS analysis of other samples provided further evidence of the presence of nitrogen in the mystery coating. The false-colored elemental maps shown here correspond to the distribution of their labeled elements in the highly magnified SEM image. The mystery coating appears as a gray band in the SEM image. Correlation again exists between the presence of nitrogen and the location of the coating. It is also noteworthy that the underside of the coating shows aggregations of lead and potassium corresponding to the area that appears bright in the SEM image. This was found repeatedly in the samples analyzed and may indicate that metal soaps (e.g. lead oleate and potassium oleate) formed within the paint and migrated to the interface between the coating and the paint layer. The combined effect of a proteinaceous layer on the paint surface and the formation of metal soaps directly underneath may well have played a key role in the complicated phenomenon that brought about the micro-cissing.

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