: Land Securities plc and Bovis Lend Lease Ltd
During the excavations at 120 Cheapside a small section of mosaic floor was uncovered in the corner of one of the trenches. The fragment was set into an opus signinum floor and consisted of a section of guilloche chain with the border for the central motif. It is likely that the mosaic dates from the 2nd century AD.
Conservators from MoLAS were called in to lift the mosaic. To protect the edges of the fragment while lifting, a long fibred paper was attached with a water-soluble adhesive to the outside tesserae. A layer of the adhesive was then brushed onto the surface of the mosaic and a layer of netting lain over the top, a second layer of adhesive was then applied and it was allowed to dry over night. This process is called facing and keeps all the tesserae in place whilst separating it from the floor.
The mosaic was lifted in a number of sections. The sections of tesserae were divided using hand tools and then metal sheets were used to undercut the object. Once separated from the mortar, each section could be lifted off site safely. To prepare the mosaic fragment for viewing, conservators will need to remove the loose mortar from the back of the tesserae, replacing it with an archival backing, and then finally remove the facing to enable it to be displayed.