Trough WK 285 Technical Analysis

Length 68 cm, Width 42 cm, Depth 23 cm

Infrared Imaging

The infra-red image above highlights a large scorch mark on the outside rim of trough WK 285. The scorch mark suggests that the object was, at one time, used in the vicinity of an open fire. Vessels of this type, including the two additional troughs included in this research may have been used for hot stone cooking. In this technique stones heated in a nearby fire are added to a liquid within the vessel. The stones are continually retrieved, reheated, and returned to the liquid until it reaches the desired temperature. 

Wood Species Identification

While this object is identified as being made from Alder in the museum notes, the method of identification is unclear. A small sample of wood was collected from trough WK 285 to confirm the museums previous identification. 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 allows us to resolve microscopic features in the wood that can help identify the particular species of tree that the spade was made from. 

The series of features outlined in the SEM images above confirm that this object is made from Alder (Alnus glutinosa) wood. 

FTIR spectral analysis showing comparison of sample collected from trough WK 285 (blue), and a reference sample for Birch ( Betula pendula ) (red)

FTIR spectral analysis showing comparison of sample collected from trough WK 285 (blue), and a reference sample for Birch (Betula pendula) (red)

FTIR Analysis

The sample of wood collected from trough 51.1935 was analysed using Fourier Transform Infrared Spectroscopy (FTIR). The spectral analysis above compares the sample from trough 51.1935 with a reference sample for European Birch wood (Betula pendula), and a reference sample for natural gypsum.

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 and position of some peaks in the spectra shown above, the sample from trough WK285 broadly corresponds with the reference sample for birch wood (included here as an generic example of a European hardwood). There is no evidence to suggest that the sample contains post-collection contaminants.