SEM-SCALE REPLICATION OF A WIDE VARIETY OF GEOLOGIC MATERIALS: CASE STUDIES IN DECAPOD CUTICLE MICROSTRUCTURE AND BUILDING DIMENSION STONES

Surface textures of fossils and weathered surfaces of dimensional stones from historic building often need to be studied at scales appropriate for the scanning electron microscopy (SEM). Removal of stone from an historic structure, or destruction of important fossil specimens to allow direct study using the SEM is not always acceptable. Replication techniques that allow SEM study of positive casts solves this dilemma by not damaging the fossil material or historic stone surfaces. Three molding compounds, two of which are designed for dental applications and one that is intended for replicating the microstructure of steel surfaces are examined. Ease of use, cost, shelf-life, effectiveness, and specimen staining or surface damage are factors that are considered. In addition, different materials and techniques used to fabricate the positive replicas must be durable enough to withstand examination under the SEM. From a paleontologic perspective, studying the microstructure of fossil decapods using a non-destructive method that can be used in museums without the need to borrow specimens is often essential. Although seemingly unrelated, the needs and conditions of work are similar to those encountered when working with soiled or weathered building stones. Weathered building stone surfaces need to be examined to determine the initial conditions before undertaking building restoration or cleaning programs with the added condition that the replication compound must work on vertical surfaces. Using replicating compounds allows examination of weathered stone or cement surfaces without the need to core or otherwise remove material from historical or aesthetic surfaces. Although replication techniques of this type are not new, improvement of techniques for examination of geologic materials using modern casting materials constitutes an important advance.