Lifting and restoring an ancient mosaic : the Medusa mosaic

Lifting

      Patrick Blanc and Marie-Laure Courboulès
 
photos © CEAlex
This pavement was lifted in nine panels. The position of the cuts, involving the removal of one row of tesserae, was determined as a function of the decoration, cracks and any lacunae.  
First cloth lining: cotton gauze
photo © CEAlex

After initial cleaning, two cloth linings were applied to the tesserae, surgical gauze and lengths of hessian, both impregnated with a polyvinyl acetate solution (figs. 1 & 2). The tesserae from the cuts were removed through the first gauze lining which keeps a certain transparence (fig. 3).
The make-up of the ancient support allowed the pavement to be loosened by inserting steel strips horizontally between the two layers of mortar, the rudus and the nucleus (fig.4). Once sandwiched between wooden planks and a wooden board, each of the nine panels could be turned over (figs. 5 & 6). For the central panel, the metal strips were inserted lower down, beneath the rudus, as it was suspected that the medallion rested on a separate support.
With the underneath of the mosaic now exposed, we began to clean away the remainder of the nucleus mortar that no longer adhered to the tesserae. Each panel thus prepared was marked with the name of the excavation site, the registration number of the pavement, the date of lifting, the number of the panel and the place of the adjacent panels (fig. 7).

During the lifting we discovered and were able to preserve the terracotta support of the Medusa emblema. This is a very precious find that provided information on the different phases of the manufacture of this mosaic (fig. 8).

1 & 2
After cleaning, applying the two cloth linings onto the tesserae, surgical gauze and lengths of hessian impregnated with a polyvinyl acetate solution.
3
The tesserae of the cuts were removed through the gauze lining.
4 et 5
Steel strips were slid between the rudus and the nucleus. The panels of the mosaic are sandwiched between wooden planks and a board.

6
Each panel is turned over.
7
The panels after lifting.
8
Reverse of the emblema.
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