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91 Chapter 7 Ethical Issues in the Molding and Casting of Fossil Specimens Janet M. Monge and Alan E. Mann Introduction The use of casts of fossil bones and teeth has a long history in paleoanthropology . Indeed, it is difficult to imagine human evolutionary studies as a comparative science without these replicas. Yet, little attention has been directed to the molding and casting techniques that produce these models or to the consequences to the original fossils that result from the molding process. In this chapter, we will address these issues; they raise broad ethical questions as well as concerns about future strategic planning. Two comparatively recent developments have led to the need to explore these matters. The last several decades have witnessed a dramatic expansion of the number of professional scholars involved in the study of human evolution (Johnston & Mann, 1997: p. 1078). This has resulted in an unprecedented increase in the number of researchers examining original fossil specimens. A related trend has been the heightened need for casts of fossil bones for teaching and comparative research. Both of these developments have serious implications for the original fossils as well as for the future of molding and casting projects. Molding and Casting in Paleoanthropology Although casts of fossil hominids1 were routinely fabricated in the nineteenth Century on specimens such as those from the Neander Valley and Trinil, little is known about the molding and casting techniques employed to make these replicas. Surviving casts from this period, for example, of the Neandertal 92 Janet M. Monge and Alan E. Mann calotte, are made from relatively soft plaster (“plaster of Paris”) that preserved little detail beyond general features of shape and size. One advantage of plaster, then as now, is that it is dimensionally stable, a quality not always present on modern casting resins, though they reproduce far greater levels of surface detail. Presumably, these early casts were made using much the same methods that were utilized by the celebrated mold maker at the British Museum of Natural History, F. O. Barlow (Grigson 1988). Barlow worked through the early part of the twentieth-century, retiring just after World War II, when he sold his sizable collection of molds to the Wenner-Gren Foundation. These have subsequently been given to the Casting Program of the University of Pennsylvania Museum which curates them for both their scientific and historic value.2 Barlow’s molding techniques, also employed by most other mold makers of the time, were elaborate, complicated, and time consuming. Molds were made using keyed wedges of plaster of paris that were built piece by piece around a fossil. Plaster was poured directly onto the highly waxed surface of the fossil (waxed to prevent the wet plaster from adhering to the bone). The sides of each plaster wedge were contoured and notched to precisely and tightly fit with adjoining wedges. Once completed, each wedge was waxed to insure that the plaster pieces remained separate (Mann & Monge, 1987; Goodwin & Chaney, 1995). Large molds, of the La Chapelle-aux-Saints skull illustrated in Figure 7.1, for example, might be composed of hundreds of these wedges, each reproducing a small section of the surface of the bone. Considering the materials employed, casts made from these molds often captured a surprising amount of detail. In the 1930s, flexible materials, like natural latex rubber, replaced plaster as the molding material. Latex proved to be a practical molding medium in some respects: it was relatively easy to use and produced molds with greater amounts of detail than earlier media. However, it often had serious shrinkage problems that resulted in distorted casts when dimensional changes were more marked in one direction than another. Casts continued to be made from plaster, but with the use of finer grained dental impression plasters, there was an improvement in the amount of detail present on the casts. Although latex continues to be available today, it has a distinct disadvantage when employed with modern casting resins. Because these materials will bond to the latex mold, heavy applications of a releasing agent are required for successful unmolding. Room temperature vulcanization (RTV) silicone rubbers became the molding materials of choice in the late 1950s. These had been developed for the tool and die industry and because they possess excellent flow characteristics , have the capability of capturing extremely fine detail. At about the same time, the use of rigid plastic resins such as polyester and epoxy became [3.142.197.198] Project MUSE (2024-04-26 11:07 GMT...

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