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Figure 5. Tracing of the heraldic crest found on six of the plates. (Mary Caruso & D. H. Keith.) Treatment

Figure 5 Tracing of the heraldic crest found on six of the plates. (Mary Caruso & D. H. Keith.) Treatment

Related Figures (9)

Figure I. The Belle site lies in 4m of water a few hundred metres north of Matagorda Peninsula. (Drawing: D. H. Keith)
Figure I. The Belle site lies in 4m of water a few hundred metres north of Matagorda Peninsula. (Drawing: D. H. Keith)
Figure 4. LG initials. Note the scribed lines above and below the letters. (Photo: Mary Caruso.)
Figure 4. LG initials. Note the scribed lines above and below the letters. (Photo: Mary Caruso.)
Figure 2. The stack of 22 nested pewter plates fused together by corrosion products and marine encrustation. (Photo: Jerry Livingston.)
Figure 2. The stack of 22 nested pewter plates fused together by corrosion products and marine encrustation. (Photo: Jerry Livingston.)
Figure 3. The maker’s mark. (Photo: Jerry Livingston.)
Figure 3. The maker’s mark. (Photo: Jerry Livingston.)
Table 1. Elements in pewter sample detected using EDXREF spectrometry The topmost and bottommost plates in the stack, and all the plates that were recovered singly, were encrusted with marine shells. The predominately cal- careous shells themselves were dissolved with dilute sulphuric acid but the cement- like exudate secreted by shellfish in order to anchor themselves to the substrate was much more resistant to normal chemical and mechanical cleaning techniques. It was determined that the material could be dissolved rapidly with a 5% solution of ammonium acetate. Subsequent exper- iments demonstrated that if an encrusted artefact were immersed in an ammonium acetate solution, the exudate would soften
Table 1. Elements in pewter sample detected using EDXREF spectrometry The topmost and bottommost plates in the stack, and all the plates that were recovered singly, were encrusted with marine shells. The predominately cal- careous shells themselves were dissolved with dilute sulphuric acid but the cement- like exudate secreted by shellfish in order to anchor themselves to the substrate was much more resistant to normal chemical and mechanical cleaning techniques. It was determined that the material could be dissolved rapidly with a 5% solution of ammonium acetate. Subsequent exper- iments demonstrated that if an encrusted artefact were immersed in an ammonium acetate solution, the exudate would soften
Figure 6. Auger photomicrograph of a freshly fractured pewter plate surface. Bulk of sample is largely homogenous. Note dark irregular inclusion (3, upper right) containing approximately 35% iron by weight (Lisa Magel).
Figure 6. Auger photomicrograph of a freshly fractured pewter plate surface. Bulk of sample is largely homogenous. Note dark irregular inclusion (3, upper right) containing approximately 35% iron by weight (Lisa Magel).
Figure 7. Schematic of stripping/polishing electrolytic cell. Stripping the artefact loosens the resistant black film, polishing reduces and brightens the cleaned surface. The plate is turned on edge to avoid trapping gasses released during electrolysis. The counter electrode is shaped to match the contour: of the plate. In order to monitor the process more closely, only one side of the plate is treated at a time (D. H. Keith).
Figure 7. Schematic of stripping/polishing electrolytic cell. Stripping the artefact loosens the resistant black film, polishing reduces and brightens the cleaned surface. The plate is turned on edge to avoid trapping gasses released during electrolysis. The counter electrode is shaped to match the contour: of the plate. In order to monitor the process more closely, only one side of the plate is treated at a time (D. H. Keith).
Table 2. Soft abrasives evaluated for final pewter polish stripping techniques, with the advantage that a worst case condition can be calcu- lated using some simple assumptions and stripping techniques, with the advantage that a worst case condition can be calcu- lated using some simple assumptions and
Table 2. Soft abrasives evaluated for final pewter polish stripping techniques, with the advantage that a worst case condition can be calcu- lated using some simple assumptions and stripping techniques, with the advantage that a worst case condition can be calcu- lated using some simple assumptions and
Figure 8. Plate no. 778-015. The right side exhibits the resistant black film that covered all the plates after gross cleaning. The left side has been electrolytically stripped and polished, but not flour polished. (Photo: Mary Caruso.)
Figure 8. Plate no. 778-015. The right side exhibits the resistant black film that covered all the plates after gross cleaning. The left side has been electrolytically stripped and polished, but not flour polished. (Photo: Mary Caruso.)
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ArchaeologyNautical Archaeology
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