Fabric pseudomorphs, formation

In order to propose a model for the process of silk fabric pseudomorph formation on the Shang bronze halberd, consideration must be given to... 

Based on a compilation of the preceding information on the probable environment in which the bronze halberd was found, a model can be proposed for the process of silk fabric pseudomorph formation. The presence of an organic material in close proximity to the bronze object alters... 

Questions that remain concerning the process of silk fabric pseudomorph formation on the bronze halberd will be resolved with further study of pseudomorphic formations, particularly on objects whose provenance is documented precisely. A more complete description of the microenvironment of the buried objects as well as a quantitative analysis of the mineral composition of the pseudomorphs is necessary for the development of equations for the chemical equilibria involved. Future work is planned to study pseudomorphs as mineralogical structures and pseudomorphs as evidence of textiles. This work includes examination of two additional Shang bronze objects currently on loan to one of the authors. 

As a form of direct fabric evidence, the physical shapes of textile fabric pseudomorphs have been studied to identify fiber type and yam and fabric construction. Pseudomorphs of paired filaments in mineralized fabric formations found on Shang-period bronze weapons were determined to be replaced silk (I, 2) S-and Z-twisted silk staple yarn pseudomorphs were identified as well as fabric constructions, including float yams and a ribbed weave. 

In addition to the analysis of physical structural characteristics of textile fabric pseudomorphs, chemical information has been obtained. On bronze and copper artifacts, the pseudomorphs are composed of malachite, tenorite, and cuprite (I, 2), the formation of which probably requires moist conditions, a corrosive metal, and optimum fiber-metal contact (I). Trace elements in their structure vary from object to object and site to site (1-3), but the relationship of these elements and the fiber, metal, and soil composition is not yet known. 

In order that interpretations of prehistoric fabric use and manufacture are soundly based, it is necessary to demonstrate that minerals formed during postburial alteration of a fabric-metal association do, indeed, replace fabric components and duplicate faithfully the shapes of the fibers, yams, and fabrics. The degree of detail to which this duplication occurs must be determined to establish limits to information that can be expected from fabric-pseudomorph study. For example, nodes on barbules of feathers, necessary for feather classification, have not been observed yet, but the mechanism of pseudomorph formation may be found capable of replicating such fine structures and thus prove useful in some archaeological studies. In addition, the relationship between pseu-... 

Little published information exists about textile fabric pseudomorphs. For the most part, those interested in the phenomenon have been concerned with the pseudomorph as textile evidence rather than with the process of its formation. There is no established methodology for examining the pseudomorph either as mineral or as textile. 

Several layers of fabric-type formations were observed in each location. It is impossible to know whether these pseudomorphs consisted of a single fabric with surface decoration or several layers of the same fabric or even different fabrics (18). The upper or top layers of the fabric formations generally contained large black yarns parallel to each other (system A). Rather consistently, the green, single-fiber yarn and the paired-fiber yarns appeared in both systems A and B or in one (system B) that interlaced with black yarns in the other (system A). Green, paired-fiber yarns also appeared occasionally along the surface in a nonrectilinear situation. 

Two types of nonrectilinear yarn formation were identified, a curvilinear yarn movement and a linear one that moved in a zig-zag, 45° angle relative to the fabric structure (Figures 6, 9). That these were identified along the surfaces of the formations suggests a surface decoration. However, until further study confirms this point, the function of system C yam formations within the fabric pseudomorphs remains uncertain. 

There is no information concerning the burial of the bronze halberd under study however, it is assumed that it must have been buried in a traditional Shang manner. Silk fabric pseudomorphs were found on the halberd therefore, it must have been placed in contact with fabric resting either on the ground, on a shelf, or on a body in the burial pit. Each of these three situations could provide a different outlook on the chemical reactions involved in pseudomorph formation. Due to lack of site information, the influence of the placement of the halberd can only be speculated upon. 

Pseudomorphs on a bronze Shang Dynasty halberd (ca. 1300 b.c.) were subjected to mineralogical analysis to determine their structure and composition. X-Ray diffraction, scanning electron microscopy, and energy dispersive analysis of x-rays were used in these analyses. Photomicrographs of pseudomorphs also were studied for fiber, yam, and fabric formations that give evidence of textiles. A model describing the process of silk pseudomorph formation was proposed. 

At approximately 5.5 cm from the crosspiece and at the edge of a crushed area, the pseudomorphs change in their geometric relationship with respect to the straight edge of side A. Between the crosspiece and the crushed area, both yarn and fabric formation exhibit a 60° angle... 

The presence of yarn-type formations from two different systems interlacing in a perpendicular relation to each other confirms a formerly woven-fabric structure for the pseudomorphs. The evidence of the pseu-domorphic fibers, yarns, and fabrics confirms the former presence of silk fabrics on a Shang Dynasty bronze weapon. Further discussion and implications of these findings fall outside the purview of this investigation future work will focus upon an analysis of specific fabric structures present on Shang bronzes. 

Two categories of pseudomorphic textile fabric formations were identified. One, the yam type, moves in and out of the second, the fabric type. At least six areas of the latter are apparent. 

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