Microfossil Type Collection Procedure Guidelines
Traditional microfossil slides (3 x 1 inch) consist of several mm thick cardboard (various thicknesses are available) covered with paper, in which a round or rectangular ‘well’ has been punched out. The microfossils are placed within the well, and one or two storage options are used: 1) the cardboard slide with its microfossil in the ‘well’ is covered with a thin celluloid rectangle (cover slip) or 2) the cardboard slide with its microfossil in the ‘well’ is covered with a (3 x 1 inch) glass slide, and cardboard and glass slide together are placed in an aluminum holder. Before the 1940s, slides were commonly homemade, and some did not have any cover over the well containing the microfossils.
Prior to the commencement of this project, much of the microfossil collection at the AMNH had non-covered cardboard slides, or slides which had lost their cover over time, and the slides unfortunately were stored vertically (i.e., on their side) in slots in wooden boxes. The microfossils were usually glued in the well with the organic glue tragacanth, but this glue dries out and deteriorates over time. Because the slides were stored vertically, the microfossils could fall out of the slide and drop to the bottom of the box. This had happened with several slides.
Loose specimens are easily damaged due to friction when slides are taken out of the box. If the cardboard slides in the collection are not placed in aluminum holders, covered with glass, and stored horizontally the collection can be lost within a few years. The combined factors of vertical storage, failing adhesives, and missing cover slides had resulted in damage to many of the specimens. The cover paper with hole of the 1-hole cardboard slide had either turned yellow or damaged over the years. This required urgent attention.
A decision was made to rehouse all slides horizontally in custom designed slide boxes. The synthetic adhesive, Jade R was chosen as a mounting medium because it is an acid free archival PVA adhesive that provides a strong bond with the advantage of being reversible with water. In addition, as an organic glue, gum tragacanth (the adhesive used previously) required the addition of formalin to inhibit mold growth. As a synthetic adhesive, Jade R doesn’t facilitate mold growth and meets museum conservation standards.
The bottom of all boxes was checked carefully to recover lost specimens. This has been successfully done on slides we have conserved in the recent past and several type specimens have been recovered.
Depending on the condition of the slide, a decision was made to cover existing cardboard slides with glass cover slides and place them in aluminum holders rather than transfer, replace or remount specimens to plastic slides (another available housing option) because the former does not involve much handling of the specimens, and the specimens do not have to be loosened from the well if they are still glued in place, thus preventing further damage to fragile specimens.
Overview of material used
Conservation and archival quality materials are being used for rehousing. Archival quality items are listed with supplier information below: