For the first time, molecular evidence of the structural role played by succinic acid within the macromolecular structure of Class Ia and Class Id resinite is presented. Using a novel gas chromatographic methodology, communol (Class Ia) and ozol (Class Id) moieties within the polylabdane matrix are shown to be cross-linked with succinic acid. Samples were analyzed using pyrolysis-gas chromatography–mass spectrometry with in situ hexamethyldisilazane derivatization, using a thermal separation probe to perform the pyrolysis and sample introduction. The relatively slow rate of heating and prolonged pyrolysis of resinites using this new methodology, combined with the use of a mild derivatization reagent, allowed communol pyrolysates from Class Ia resinite and ozol pyrolysates from Class Id resinite to elute with unbroken succinyl ester cross-linkages. These results provide direct molecular evidence that the key role of succinic acid within Class Ia and Class Id resinite is to cross-link the macromolecular structure. In the Class Id resinite, the methodology also allowed the detection of succinyl ester linkages between ozol pyrolysates and dehydroabietol, thus demonstrating that nonpolymerized diterpenes contribute structurally to the macromolecular structure of Class Id resinite.

This article describes the identification of a hafting adhesive on an antler point, slotted for microblade insertion. The adhesive, found in the slots of the point, would have held the microblades in place. Radiocarbon dated to 7310 ± 40 B.P. (uncalibrated), the point is one of the oldest and best-preserved artifacts recovered from the melting alpine ice patches in southwestern Yukon, Canada. Because the artifact was frozen, the organic components have not degraded and a detailed chemical analysis was possible. Analyses of residue in the slots of the point by Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry showed that a conifer resin adhesive was used. The high concentration of diterpene resin acids with an abietane or pimerane skeleton confirmed a Pinaceae source for the resin. There were no chemical markers to indicate that the resin had been strongly heated to produce tar or pitch. Based on a comparison with five Pinaceae resins from trees common to southern Yukon, the resin from the slotted point most closely resembles the chemical profile of spruce (Picea sp.). The identification of this hafting adhesive on a slotted point adds significantly to our understanding of early hunting technology in Yukon.

Paintings and painted objects are quite susceptible to degradation, as paint layers are usually composed of complex mixtures of materials that can participate in chemical degradation processes. The identification of the constituent materials in paint (including binders, pigments, and fillers) and the degradation products within paint layers is of particular importance to ensuring the conservation of paintings, by providing important information both about their material history as well as their state of conservation. Metal fatty acid salts (metal soaps) are degradation products that can form in situ from interactions between inorganic pigments and free fatty acids in oil-based binding media, and can cause significant condition issues in paintings. Fourier transform infrared (FTIR) spectroscopy is one of the leading analytical techniques for the study of metal soaps. In this article, the materials analysis of several cross-sections from paintings and painted objects from works in Canadian collections is presented. Recent results on the use of external reflection FTIR (R-FTIR) spectroscopy to identify and map the distribution of paint components and metal soap degradation products is presented. In particular, zinc, lead, calcium, and copper fatty acid salts were all readily identified in paint cross-sections by R-FTIR spectroscopy, along with several pigments and the oil binding medium. The results shown here are among the first detailed examinations of these metal soaps in paint cross-sections using R-FTIR spectroscopy. The use of highly polished samples in which specular reflection is dominant allowed for spectral transformations to be applied to generate transmission/absorption-like spectra which facilitated identification of these species. The distribution of these species across the cross-sections was mapped by integrating characteristic absorption features in the R-FTIR spectra. Attenuated total internal reflection (ATR) FTIR spectroscopy was also performed on several samples, which provided additional compositional details at the interface of paint layers and degradation products.