Following on from our recent blog post, Turning over a new lid, Jill Saunders’ latest entry reveals how scanning electron microscopy analysis helped identify the different materials, both on and inside the iron coffin from St Bride’s. Read on to find out more…
In blogs to date you may have noticed that I have often said ‘suspected leather’ regarding exterior decorative features, and have merely suggested possible identifications for material from the coffin interior such as sawdust, woodchip, straw or hay. Our socio-historical research into burial methods and coffin manufacture, together with macroscopic (with the naked eye) and low-magnification visual examinations, have allowed us to make educated guesses. However it is crucial not to take these conjectures for granted unless you can observe definitive attributes, which are often only clear under very high magnifications such as scales on hair fibres. In terms of conservation, incorrect assumptions could lead you to misunderstand all sorts of information about structure and likely condition, which obviously would hinder your ability to tailor the best possible conservation approach to the material at hand eg electing a suitable consolidant. Further, incorrect identifications could lead to misguided historical conclusions, whereas correct knowledge about materials present would be valuable information.
Fig. 1 A summary of samples taken with accompanying images
We decided to take samples from key materials (Fig. 1) and examine them with images generated through SEM (scanning electron microscopy) analysis. The organic samples were gold coated to generate clear images more easily. The tiny losses needed for a sample from an object of this size would be negligible and well worth it for the sake of generating data, which could lead to positive identifications. Additionally the coated samples on their staves have all been saved and filed, ready and available for future analysis so that theoretically more need never be taken.
Summary: Coarse textile
The images reveal the same simple weave visible to the naked eye:
The fabric seems to be composed of two different fibres. One is animal hair, probably wool, with characteristic scales, and appears one is plant material:
They seem very much interwoven, like a coarse matting material made from fibre scraps:
The material appears to be a cheaply made type of coarse matting. The presence of animal hair/wool was surprising as this could not be discerned with the naked eye and, though we knew the material was organic, we had thought it would be entirely plant based.
Summary: Suspected hay/straw
Under high magnification, the material, which had the appearance of thick hair to the naked eye, looks like rough wood chips of different types of wood.
The sample appears to be a plant based coarse packing material, but more research is needed to identify some of the images captured.
Summary: Suspected leather
We took two samples in order to image the upper side and underside of the suspected leather:
Watch this space for the next entry covering the application of lacquer to the coffin lid: Lacquering the lid.