Following on from our recent blog post Coffin decoration & Mrs Campbell, Jill Saunders tells us more about the conservation work on the iron coffin from St Bride’s, focusing on the lacquering and consolidation of the main coffin.
Dust removal, corrosion and encrusted debris reduction and lacquering of the lid now complete, we set our sights on the more complex coffin base, which we had cleared of debris but were yet to clean. As explained in previously blog entries, this object had fragile decorative remains on outside walls as well as intricate interior extant components:
A key concern was the preservation of the external decoration (Fig.1). As it was so fragile and vulnerable to loss, we decided that this is where we should first direct our attention. The lacquering had worked well to secure and accentuate features on the lid. But before we could add this coating material we wanted to reduce the dust, bulbous corrosion products and debris on the external surface. Though the removal of material from an object can always be viewed controversially, we felt this level of cleaning was justified to protect the integrity of the material remains and help to communicate its features to the viewing public. Again we used a brush and object vacuum, with netting over the funnel in case of loss, and a stiff brush and Garryflex, being careful not to disturb the features, before applying the same conservation grade acrylic resin which we had used to lacquer the lid.
During this process we discovered areas of a dull, pale silver metal; the same in appearance as we had found in places on the lid (Figs. 6 & 7). This metal was a thin sheet directly on top of the iron and beneath the remains of decorative elements. We knew that wooden caskets of the time often had lead sheeting and so we conducted a chemical spot test to support this theory, which gave a positive result (Fig. 8). As previously stated in the Coffin decoration & Mrs Campbell blog post, chemical spot tests are indicative only and materials science analysis such as SEM or XRF would be needed to certify elemental information. However, the historical context and properties of available metals also strongly indicated the use of lead for this type of sheeting.
After lacquering the outside we turned to the inside which, like the lid had quite a lot of dust and bulbous crusty corrosion products which we wanted to remove (Fig. 9). We covered internal features at the base and the head as well as a few fabric patches attached to the walls to protect them before following the same methodology of brushing and vacuuming, using a scalpel occasionally to reduce stubborn corrosive mounds protruding from the surface. The inside walls were now ready to be lacquered but we felt that this process could wait and wanted instead to deal with the loose and friable interior features at the head and base. Very light brushing and vacuuming provided final dust reduction, but the material was so loose we soon reached a point where we had to accept some minimal dust remains so as not to cause unacceptable material loss and damage. We decided to consolidate these regions to keep them intact and secure and we had plenty of samples of the uncontaminated materials if needed for future analysis. We used a conservation grade polyvinyl resin and applied it with pipettes so that no potentially destructive contact with the material was necessary. For example, as would have been caused by brush application.
(N.B. most of the shine is because it is freshly applied and still wet).
Once these areas had been secured we progressed to lacquering the interior walls and the base. The majority of the object was now complete but we still needed to address the issue of the base, which in places was detached from the walls of the coffin and needed structural support.
Watch this space for the next entry covering work conducted to support the coffin base: Bottom heavy hazard.