Buechler, Walter K. .
Alternative Leaf Clearing and Mounting Procedures.
Chemically cleared leaves are an important tool for identifying fossil leaf remains. Collections with thousands of specimens are at the Yale Peabody Museum, the Smithsonian Institution and the University of California Museum of Paleontology. Some of the older specimens are degrading due to oxidation of the mounting medium Permount. Traditional clearing methods use potentially dangerous chemicals (toluene) and a controlled substance (chloral hydrate). The purpose of this study was to find alternative clearing and mounting procedures that would result in long-lasting, archival-quality specimens. Transparency of the final specimen depends on closely similar refractive indexes of cell wall cellulose (r = 1.47) and the mounting medium. Toluene-based Permount can be replaced by cedar oil or synthetic immersion oil, making the use of toluene for clearing and staining unnecessary. To prevent the oil from leaking, glass plates are replaced by thin, flexible acetate or Teflon foils. Cedar oil mounted specimens are self-sealing, because the highly volatile components of the oil evaporate from the margin area and the residual fraction glues the foils together. Because synthetic immersion oil does not evaporate, such specimens have to be sealed with a pressboard frame. Cedar oil mounted acetate foil specimens show no signs of degradation after four years. Immersion oil mounted Teflon foil specimens have been used for about one year and have not leaked or otherwise changed during that time. Based on general experience with synthetic immersion oil and Teflon, and from specifications by manufacturers, these specimens may have archival quality and a lifetime of potentially more than 30 years. Degrading Permount specimens can be dismantled in xylene and re-mounted in immersion oil between Teflon foils. The immersion oil mounting method can also be used for well preserved fossil leaf compressions.
1 - 1192 E. Braemere Rd, Boise, Idaho, 83702, U.S.A.
Presentation Type: Paper
Location: Maybird (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 2:30 PM