AIC's 46th Annual Meeting

Fiber cross-section observation is often essential when characterizing and identifying plant fiber artifacts. A number of bast fibers and leaf fibers have very similar morphologies in the longitudinal direction but they differ more distinctively from each other in cross-section features. Most of the existing methods of fiber or yarn cross-section sample preparation, for either light or scanning electron microscopic (SEM) observations, are not designed for handling fragile archaeological materials. The aim of this research project was to identify and develop effective fiber or yarn cross-section preparation methods which can be used for studying fragile archaeological textile objects. This study compared three fiber or yarn cross-section sample preparation methods for SEM observation including epoxy embedding, modified plastic fiber cross-section plate and free-hand as well as another three methods for light microscopic (LM) observation, including epoxy embedding and ultra-thin cross-sectioning, free-hand sectioning of embedded fiber or yarn sample and Precision Cross-section Microtome. All these methods were applied to the same archaeological textile remains retrieved from an early 16th century shipwreck site. Several known fiber or fiber plant samples were also studied for reference purposes, including hemp, jute, sisal, abaca, stinging nettle and flax. The SEM results showed that the adoption of a plastic cross-section plate designed for LM usage was the most effective fiber or yarn cross-section preparation method. The plate is cheap and easy to use. Either fiber or yarn samples can be placed into the 1-2 mm holes within the plastic plate using a known synthetic fiber as buffer or protection around the archaeological fiber sample. As to the three methods for LM observation, the most efficient method was free-hand sectioning of fiber or yarn embedded in common slide preparation solution. When dealing with very fragile sample, however, the best method was epoxy resin embedding and ultra-thin cross-sectioning (1 micrometer). This method minimizes sample distortion and keeps the sample intact. However, a phase contrast microscope is needed for observing and imaging the obtained ultra-thin cross-section samples. Based on all the cross-section images obtained from both archaeological textile samples and reference fibers or fiber plant samples, we recommend using yarns to prepare cross-section sample for either SEM or LM observation when possible. The cross-section of yarns could provide not only fiber information but also other plant tissue cell characteristics. The later can be critical when identifying a specific fiber plant. When studying very fragile archaeological textile material, we recommend the method of epoxy embedding and ultra-thin sectioning, although this method is most time consuming. The other two methods using plastic fiber cross-section plate for SEM observation and free-hand sectioning of embedded sample for LM observation are quick, easy, effective and applicable to most of textile materials. Finally, the results of this project demonstrated again that fiber cross-section study is essential when identifying and characterizing archaeological plant fiber artifacts.