Spade 1969.678 Technical Analysis

Length 58cm, Width 16.5 cm, Depth 3.4 cm


Wood Species Identification

A small sample of wood was collected from spade 1969.678. A sub-sample was cut into thin slices known as 'sections', and mounted for examination using a scanning electron microscope (SEM). The scanning electron microscope can resolve microscopic features in the wood that can help identify the particular species of tree that the spade was made from. 

The features described in the SEM images above indicate that spade 1969.678 indicate that the objects is most likely made from Birch (Betula pendula) wood. Sclariform perforation plates, a feature found in only four native Irish tree species Alder, Birch, Hazel, and Holly-  are visible in three of the images above. The number of individual bars on each plate ranges from 10 and 20, as commonly found in Alder and Birch wood. The transverse section shown above has a pore distribution consistent with that found in Birch (Betula pendula) wood


FTIR spectral analysis showing comparison of sample collected from spade 1969.678 (blue), and reference sample for Birch ( Betula pendula ) (red)

FTIR spectral analysis showing comparison of sample collected from spade 1969.678 (blue), and reference sample for Birch (Betula pendula) (red)

FTIR Analysis

The sample of wood collected from spade 1969.678 was analysed using Fourier Transform Infrared Spectroscopy (FTIR). The spectral analysis above compares the sample from spade 1969.678 with a reference sample for European Birch (Betula pendula) wood . As the predominant component of plant fibres is cellulose, and other major constituents (hemicelluloses and pectins) are also polysaccharides, the FTIR spectra of different cellulosic plant materials are superficially similar and cannot be readily distinguished by eye. In addition, degradation of one or more components of the plant material e.g. through oxidation of the cellulose molecule, will influence the position and intensity of spectral peaks relative to non-deteriorated reference spectra.

There are, however, a number of fairly consistent spectral peaks indicative of cellulosic carbohydrate within a sample. The majority of cellulosic carbohydrates will exhibit a broad band from 3600–3100cm-1 arising from O-H stretching in bound or absorbed water. A broad band relating to C-H stretching from aromatic hydrocarbons at 3100-3300 cm-1 can be obscured or partially obscured by the broad O-H stretching band described previously. Additional peaks relating to the cellulose component of plant material include peaks for C-H stretching of methylene groups between 3000 and 2800cm-1, C-H deformation in cellulose and hemicellulose at 1371cm-1, C-H vibrations at 1319 cm-1, an intense peak at about 1030cm-1 relating to C-O bonding (this is typically a combined peak for cellulose and hemi-cellulose), and a shoulder at 897cm-1 relating to C-H bending. Additional shoulders at 1155cm-1 and 1105cm-1 on the C-O band at about 1030cm-1 relate to stretching and contraction (so called ‘breathing’) vibrations within the benzene rings, and glycosidic linkages between carbohydrate molecules respectively.

While there are some minor variations in the intensity of some peaks, the spectrum for 1969.678 corresponds closely with that for Birch (Betula pendula) wood. There is no indication that the wood contains post-collection contaminants.