Enameled copper cross

Cross. The principal object studied in this investigation is shown in Figure 1, a previously unpublished photograph of a champleve-enameled copper cross with a relief figure of Christ. The cross is in the collection of the World Heritage Museum of the University of Illinois at Urbana-Cham-paign. 

The present study suggests that the coloring agents in the enameled copper cross examined, judged to be medieval from stylistic considerations, may be primarily compounds of copper. However, there was also a strong back-... 

The enameling was done in red, light blue, dark blue, green, and white. Considerable gilding remains on the unenameled copper. The enamel layers are appreciably thinner than those on the cross just described. 

A preliminary analysis of the multicolored area above the right arm of the cross revealed primarily copper and lead in the enamel. The substrate of the cross (Figure 3) and the copper corpus (Figure 4) showed no detectable zinc or tin. 

Figure 5. XRF spectrum from the cross. The green enamel near the upper arm showed major copper and lead peaks.

XRF spectra were also taken from the copper corpus attached to the cross and from an exposed region of the copper substrate from which a small piece of enamel had fallen away (Figures 3 and 6). Only copper and a small amount of lead were detected in the corpus, whereas the exposed substrate contained a high amount of copper with a very small amount of lead (about 1%). 

The enamel on the reliquary, which is thinner than that on the cross, gave strong copper signals in all cases. The red spot showed only copper, and the light blue enamel contained iron the spectrum of the green enamel showed small peaks for nickel and gold. No lead was detected in any of the enameled areas on the reliquary. 

On the basis of XRF studies, the colors of a typical medieval Limoges enamel cross are attributable to copper compounds added to the glass composition,... 

The copper sheet beneath the enamel cross contains little lead zinc and tin are not present,... 

Miscellaneous Extrusion-Applied Polymers. As mentioned earlier, there is a tendency to develop solventless magnet wire enamel formulations, and extrudable polymer systems would fulfill that requirement. There have been reports about extrusion of thin coatings of polyesters over copper wire. At this point, the state of the art allows extrusion of thin insulating films only with thermoplastic materials. The reliable extrusion of uniform and concentric insulating films of approximately 0.001-0.002 in. wall thickness is already an improvement over the more traditional extrusions of polyethylene, poly(vinyl chloride), and several fluoropolymers in much greater wall thicknesses. Because cross-linked insulation is ultimately required for most magnet wire applications, further materials development needs to be done to provide polymer compositions that are both extrudable as thin films and can be cross-linked in an economical process suitable for large-scale industrial application. 

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