Losset 67.1947 Technical Analysis

Length 73 cm, Width 53 cm, Depth 6cm

Multispectral Imaging 

Infra-red imaging of losset 67.1947 highlighted the presence of large rays in the wood. Oak has some of the largest rays of any native Irish wood species (visible as dark 'flecks' in the wood), and their presence in this object is consistent with a prior wood species identification for this object (Scannell, 1980). 

 

Wood Identification

A small sample of wood was collected from the underside of losset 67.1947 (see annotation 1 on the model above). This object was carved from a large tree trunk, with the long axis of the object aligned with the longitudinal axis of the tree.  Given the orientation of the object in relation to the tree trunk from which it is formed, the sample was collected from a region of wood that contains some of the 'newest' growth rings available for this object. In addition, as the sample location corresponds with a split in the wood on the underside of the object, collecting the sample from this region has minimised the visual disruption to the object. 

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  help to identify the particular species of tree that the losset was made from.

The tyloses filled vessels shown in the images above, and the large rays visible in the infra-red image (top)are consistent with a prior wood species analysis for this object as Oak (Quercus robur) wood (Scannell, 1980).

 

FTIR spectral analysis showing comparison of sample collected from losset 67.1947  (blue), a reference sample for Birch ( Betula pendula ) (red), and a reference sample for natural gypsum (green).

FTIR spectral analysis showing comparison of sample collected from losset 67.1947  (blue), a reference sample for Birch (Betula pendula) (red), and a reference sample for natural gypsum (green).

FTIR Analysis

The sample of wood collected from spade 67.1947 was analysed using Fourier Transform Infrared Spectroscopy (FTIR). The spectral analysis above compares the sample from spade 67.1947 with a reference sample for European Birch wood (Betula pendula), and a 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.

In addition to the peaks associated with wood, a number of addition peaks indicate the presence of CaSo4 (gypsum) in the sample. These include antisymmetric and symmetric O-H stretching bands between 3700 and 3200 cm-1, a strong SO4 stretching band between 1140 and 1080cm-1, and an SO4 bending band around 620cm-1 (Derrick et al. 1999.  As gypsum is a constituent of some types of Irish peat, it seems likely that it's presence here relates to minerals embedded into the object during use or burial.  

A number of smaller samples were collected from losset 67.1947 as noted on the interactive model above. The museum record for this object noted that when the object was discovered, a leather patch had covered the hole in the object, but had quickly deteriorated and is now lost. Unidentified fibrous material was collected from within the small holes surrounding the larger hole in the object, and from some of the small holes on either side of the longitudinal break in the object. 

Bibliography

Derrick, M. R., Stulik, D. and Landry, J. M. (1999) Infrared Spectroscopy in Conservation Science. Getty Conservation Institute.

Scannell, M. (1980) Report on wooden trays, methers and other objects from Armagh Museum. Department of Agriculture and Fisheries, Dublin, Ireland.