Academic journal article Estonian Journal of Archaeology

Investigation of the Adhesive Residue on the Flint Insert and the Adhesive Lump Found from the Pulli Early Mesolithic Settlement Site (Estonia) by Micro-ATR-FT-IR spectroscopy/Pulli Asulakohast Leitud Tulekivist Pistiktera Kiti Ja Kitikamaka Uuringud Mikro-Atr- Ft-Ir-Spektroskoopia Meetodil

Academic journal article Estonian Journal of Archaeology

Investigation of the Adhesive Residue on the Flint Insert and the Adhesive Lump Found from the Pulli Early Mesolithic Settlement Site (Estonia) by Micro-ATR-FT-IR spectroscopy/Pulli Asulakohast Leitud Tulekivist Pistiktera Kiti Ja Kitikamaka Uuringud Mikro-Atr- Ft-Ir-Spektroskoopia Meetodil

Article excerpt

Introduction

Combined tools made of organic and mineral materials were used across extensive regions in Eurasia during the Stone Age (e.g. Rimantene 1971, 164 ff.; Matyushin 1989, 130; Oshibkina 1997, 69; Vankina 1999, fig. XXIX). In functional sense we are mostly dealing with either arrow- or spearheads, in less frequent cases daggers or other tools. In the Baltic Sea region mostly combined tools were used during the Mesolithic, especially in its earlier phase. These tools were made by attaching inserts of flint (rarely quartz) to grooves carved into bone (or wooden?) points (e.g. Apals et al. 1974, plate 1; Jaanits et al. 1982, 30). Although such combined tools are rarely found, the inserts are discovered frequently. Adhesives were used to attach the inserts to the points, in few cases the remains of the adhesive have also been preserved. From some Stone Age sites in Scandinavia, Finland, Russia, Germany and Switzerland, adhesive lumps were found, sometimes with chewing marks (e.g. Vilkuna 1963; Apals et al. 1974 and references therein; Mikhail C. Zhilin pers. com. Aprill 22, 2009).

It is generally assumed that the adhesive was made of mixtures of (fir or pine) resin, birch bark tar, beeswax, fat, etc. (e.g. Jaanits et al. 1982, 30; Regert et al. 2003, 1622). In particular the use of birch bark tar has been emphasized, sometimes in combination with other materials (Stacey 2004, 1 and references therein). Nevertheless, there is no sufficient data available to make broad material usage generalizations across different areas of Europe. Therefore, the remains of adhesive found from Pulli, two cases of which will be discussed as follows, are definitely interesting for the wider public.

A flint insert with adhesive remains on it has been found from the Pulli Early Mesolithic settlement site (Fig. 1) in south-western Estonia, radiocarbon dated to 8700-8550 cal BC (Veski et al. 2005, table 2). This small (18 x 8 x 2 mm) microlith (AI 4476: 1042) is made of blackish brown flint blade knapped from creataceous flint. One of its edges is retouched and the end can be distinguished as a barb. There are remains of black adhesive on the surface of the artefact. From the same settlement site some small black lumps have also been found, which are probably pieces of adhesive. One of the lumps (1) (AI 4476: 662) is of irregular oval shape (49 x 16 x 13 mm, 5.2 g.) (Fig. 2) and has smooth surface.

The goal of the analyses was to determine the chemical composition of the flint insert and the black adhesive layer on it and of the adhesive lump, and also to determine whether the composition of the adhesive on the insert is similar to the lump. The samples were analysed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR spectroscopy).

Infrared spectroscopy is an effective analytical method to study both organic and inorganic compounds. The vast majority of materials (e.g. oils, waxes, resins, proteins, inorganic additives etc.) absorb infrared radiation and have rather characteristic infrared spectra (Regert et al. 2003; Vahur et al. 2005). Thus, classes of compounds can almost always be identified, in most cases even in mixtures. Identification of individual compounds in their pure forms is in many cases also possible. However, identification of individual compounds in mixtures is often difficult (depending on the complexity of the mixture).

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

There are various techniques of sample handling used in IR spectroscopy. The reflectance techniques such as ATR (Attenuated Total Reflectance) are increasingly used. ATR FT-IR spectroscopy is a non-destructive, fast and convenient method often requiring minimal sample preparation. With micro-ATR accessory it is possible to use very small sample size and the IR spectra can be measured directly from the sample surface. These are the reasons why micro-ATR sampling method was chosen for the present investigation. …

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