Adhesives for Fossil Preparation

Compressions of fossil leaves on marl blocks soaked with water are tricky palaeobotanic findings to deal with. In
fact, this peculiarity makes the findings exposed to serious degradation: the evaporation of water causes shrinkage of the matrix
and the leaf leading to fragmentation, delamination and exfoliation of the fossil, until its final disappearance. The aim of this
research was to identify a consolidation method which satisfies museum needs and can be utilised for all conditions of hydration
of the object. Following a survey of several natural science museums in Northern Italy, Paraloid™ B72 and PEG4000 along
with other resins never previously used on this kind of fossil were tested. At the end of the research, two products gave adequate
or good results, preserving the leaf from further degradation whatever the hydration condition of the object: the acrylic resin
Paraloid™ B72 and a polyurethane resin.

The delicate nature of the specimens at Florissant Fossil Beds National Monument, Colorado requires a constant monitoring of the collections. The overall stability of the fossils is greatly impacted by the abrupt change in humidity that may occur after the paper shale has been excavated, as well as the varying levels of humidity in the collections and display areas. Creating methods to effectively “acclimate” the shale’s transition from the ground to the lab, and finding and maintaining the ideal humidity range for our collections room is integral to the collections management at Florissant Fossil Beds. For these experiments, a controlled environment chamber was used, employing both humidification and dehumidification systems. The humidity is systematically lowered to slowly dehydrate
damp shale and safely lower it to the ambient relative humidity (RH) in the lab and collections areas. Tests have also been run to monitor damages the shale undergoes when it reaches a certain level of humidity. Below 25% RH, deformation occurs in the form of flaking and delamination. Initial data suggest that the ideal range to keep the collections area is between 30-35%. These tests will ultimately become the basis for a protocol that will outline how the paper shale will be handled once excavated, and how the collections area should be maintained.

The establishment of the Florissant Fossil Beds National Monument, Colorado, in 1969 allowed for the protection and preservation of its unique and delicate fossil specimens, the majority of which are plants and insects. Thousands of fossils have been excavated and collected during the past 130 years and are a part of many museum collections worldwide. These include those from conglomerate, paper shales and other types of rocks, though the paper shale has proven to be the most fragile. Unfortunately, the preparation methods used by early collectors on specimens from the paper shales have proven to be irreversible and do not meet contemporary museum conservation standards. The scientific value of some specimens, including holotypes, has been significantly diminished due to their deterioration after preparation. Current preparation techniques consider the rock matrix as well as the type of fossil (by taxonomy, uniqueness, etc.) and its preservation condition. Florissant is especially unusual as the majority of its fossils are preserved in the extremely thin paper shale layers, often only 0.1 mm in thickness. This type of matrix is particularly vulnerable and easily damaged during physical preparation and chemical conservation. There is no single existing standard procedure that has been adapted specifically to Florissant. Tasks beyond the removal of excess rock matrix on or around the fossil include repairing damage (microflakes ≥ 10 sq.mm, cracks, breaks) caused by field collection and during preparation, as well as constructing small cradles within specimen boxes to support and secure fossils during transportation, storage, and study. The main preparatory tools and materials used are the Micro Jack 1 (Paleo Tools), acryloid, pin-vises with various tips, a microscope, ethafoam, small, flat pieces of non-fossiliferous shale and an air puffer made from an aquarium pump and an intravenous drip set with a needle. Future preparation research will focus on testing several possible adhesive and consolidant regimens for the conservation of Florissant specimens in general and paper shale situations in particular. Non-fossiliferous shale specimens (uncataloged) will be used for testing different polymers at different solutions and viscosities to establish the best materials for use. Reversibility is a secondary consideration for these specimens. The main consideration is stabilization so that the tiny fossils are not irrevocably damaged or destroyed. Current preparation techniques at Florissant serve the short-term needs of stabilization; however we feel that future research will perfect our methods and materials. This holds potential to develop more effective techniques that will better fulfill the collective mission of the Monument and all other institutions in possession of Florissant specimens to conserve these fragile and important fossil resources.