Spade 287.1947 Technical Analysis

Length 125.7 cm, Width 19.5 cm, Depth 2.7 cm

 

Multispectral Imaging 

Multi spectral imaging revealed the presence of what is likely a post collection repair on spade 287.1967. The darker coloured wood used in the lower section of the blade in the images above has a somewhat different texture and grain direction to the rest of the blade. The UV image above highlights a band of fluorescent adhesive along the join between the two different wood sections which suggests that the spade was repaired or restored some time after it was collected. The wood sample collected from spade 287.1967 deliberately avoided the lower section of the images above, as this was considered to be a more recent addition.

 

Wood Species Identification

A small sample of wood was collected from spade 287.1967 as shown in the 3-D model above. A sub-sample was cut into thin slices known as 'sections', and these were mounted for examination using a scanning electron microscope (SEM). The scanning electron microscope can resolve microscopic features in the wood that help identify the particular species of tree that the spade was made from.

Unfortunately the wood collected from this spade was in poor condition, and wood species identification is as yet inconclusive. The image above, showing what appears to be inter-vessel pitting,  indicates that the spade is made from hardwood. The indistinct nature of the wood microstructure in this sample precludes more detailed species identification for this object.

 

FTIR spectral analysis showing comparison of sample collected from spade 284.1967 (blue), and reference sample for Birch ( Betula pendula ) (red)

FTIR spectral analysis showing comparison of sample collected from spade 284.1967 (blue), and reference sample for Birch (Betula pendula) (red)

FTIR Analysis

The sample of wood collected from spade 287.1967 was analysed using Fourier Transform Infrared Spectroscopy (FTIR). The spectral analysis above compares the sample from spade 287.1967 with a reference sample for European Birch wood (Betula pendula). 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 between the spectra, the spectrum for 287.1967 corresponds with that of woody cellulosic material. There is no indication that the wood contains post-collection contaminants.