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Preparing the tabletop for consolidation
Preliminary studies revealed that more than 85% of the surface of the mosaic separated from the base. Due to the destructed mastic, numerous voids were formed under it. To consolidate the mosaic, it was decided to fill the voids with glue. After drawing a map of the state of preservation we made a "conductor": a sheet of transparent 5 mm thick Plexiglas the size of the tabletop. In the areas where the mosaic was separated, and in areas of black marble, 1 mm holes were drilled through the conductor.
Marking of holes and glue application
The drilled holes were marked. Plasticine rolls were installed to glue the cavities, providing glue supply during the vacuum process. The tabletop voids were filled with special glue using thin needle syringes.
Vacuuming
To ensure maximum filling of the voids, the top was placed in a specially manufactured vacuum chamber. Vacuuming was carried out in stages. During the step-by-step vacuuming process, the adhesive filled all the small voids.
Gluing the surface
To fill even small areas of where the glue peeled off and consolidate the joints of the mosaic, a layer of adhesive was applied to the surface of the top placed in a vacuum chamber. The top was then vacuumed again.
Removal of glue residue from the Florentine mosaic surface
Residues of liquid glue were removed from the surface with dry paper towels.
Making lapis lazuli hearts to replace the lost ones
All four corners of the tabletop were badly damaged: one heart was completely lost, the other was 40% preserved, and the remaining two lost edging details of Sienna yellow marble. Lapis lazuli was chosen to restore the lost heart, matching the original one in colour and quality. A template was glued to the surface of a specially prepared lapis lazuli plate. It was shaped with a facing machine. Lost elements of lapis lazuli and Siena marble were made for the other parts of the hearts.
Installing the lapis lazuli hearts
The three preserved hearts with restored Siena marble edges and lapis lazuli details, as well as one newly made heart, were installed using tinted glue. Special attention was paid to matching the surfaces of the restored parts with those of the top.
Filling the joints and chips
The joints of the restored and original parts of the top were filled with tinted glue. To level the surface, a lavsanic film was placed on the applied glue. The film was smoothed with spatulas so that all air bubbles were removed from under it and the level of glue left under the film was no higher than 0.2 mm above the level of the mosaic. The big chips on the side of the tabletop, as well as the chips on the corners were restored using the same method.
Sealing the holes
The holes left after consolidation of the surface were filled with tinted glue. To improve adhesion of the glue, existing holes were re-drilled to a depth of 0.5-1.0 mm. A drop of tinted glue was then placed in each hole using a thin needle. The surface was then carefully smoothed out.
Restoring the colour of the stone background of the tabletop
In order to restore a uniform stone background of the Florentine mosaic, linseed oil was applied to the surface of the tabletop, tinted with a carbon black dry pigment. The remnants of the oil were removed from the surface with paper towels.