Variation in the Deterioration of Fossil Resins and Implications for the Conservation of Fossils in Amber

Abstract

The deterioration of fossil resins (crazing, cracking, and darkening) was investigated by comparing the effects of one year of accelerated aging-specifically intensive exposure to light, heat, and fluctuating humidity, both individually and in combination-on samples from several natural resin deposits. These included two Cretaceous ambers (from Myanmar [Burma] and central New Jersey), two Tertiary ambers (from the Baltic and the Dominican Republic), and Holocene copal from Zanzibar. The five resins were chosen for their disparate ages and botanical origins (and thus chemical and physical properties), as well as their paleontological significance. In all cases, pronounced deterioration occurred under combined exposure to light and fluctuating humidity, based on surface crazing and a decrease in absorbance of light in the UV region (360-400 nm). While crazing did not visibly occur in cases of fluctuating humidity in dark conditions, or UV exposure alone, spectrophotometric evidence indicates that some deterioration did take place. Yellowing after exposure to elevated temperatures occurred in all samples tested, with the exception of Burmese amber. All four true ambers exhibited a decrease in UV absorbance after exposure to heat (while copal actually showed an increase). The samples from the five deposits

Collection management and study of microscope slides: Storage, profiling, deterioration, restoration procedures, and general recommendations

“…Oxygen was supposed to contribute to the deterioration of amber as well (Thickett et al 1995) and has been demonstrated to actually do so by chemical analyses (Pastorelli 2011;Pastorelli et al 2012). Exposure of amber of various origin to accelerated aging by light, heat, and fluctuating humidity over one year lead to increased visible or only spectrophotometrically detectable deterioration of the amber, including crazing of the surface, cracking, and darkening; Bisulca et al (2012) favored especially a stable relative humidity as prerequisite of long-term storage of amber. An accelerated aging study at 70°C contributes to understanding the mechanisms, by which the polymer degrades (Pastorelli et al 2013).…”

“…The Conservation and Preservation of Natural Science Collections Project of the National Institute for the Conservation of Cultural Property, USA suggests inter alia a technology transfer from related disciplines like chemistry, physics, materials science, and conservation science to natural history collections (Duckworth et al 1993). Such efforts have been seen in amber collections, and specific studies have been designed to understand better the effect of environmental parameters on the deterioration of amber (Thickett et al 1995;Pastorelli 2011;Pastorelli et al 2011Pastorelli et al , 2012Pastorelli et al , 2013Bisulca et al 2012). These observations on amber are quite indicative for the storage conditions of microscope slides mounted in natural plant resins like Canada balsam, which has been used as mounting medium for more than 180 years now (Bracegirdle 1978, p. 88).…”

An enigmatic piece of amber in the Oligocene of the Assam-Arakan Basin (Eastern India)

“…Recent developments in amber research highlighted that the scarcity of amber is a myth and that amber is worldwide distributed (Penney, 2010). On the contrary, the second preconception (fragility) is not a myth, as shown by management issues with amber collections (Bisulca et al, 2012;Girard et al, 2012). However, little is known about this special point, and the sample studied here highlights that, besides its apparent fragility, amber is a rather robust material that can survive anchimetamorphism.…”

New eurymeline leafhoppers (Hemiptera, Cicadellidae, Eurymelinae) from Eocene Baltic amber with notes on other fossil Cicadellidae

“…Morphological characters were assessed by examination of the specimens using an Olympus SZX-12 dissecting microscope. Specimens were prepared by grinding flat facets in strategic locations to obtain a clear field of view for detailed photomicrographs according to Nascimbene and Silverstein (2000) and Bisulca et. al.…”