by Ted O’Neill
Cocciopesto is a waterproof building material used as a wall-covering and a floor-covering in water tanks and aqueducts. It is commonly confused with, but recently identified to be different from Opus Signinum (‘Segni-style masonry’). It is characterised by fragments of crushed or ground terracotta from tiles, bricks or crockery mixed with a lime-based binding agent like modern cement. The small pieces or shards of terracotta are known as ‘cocci’ (pronounced ‘cochi’) and it is from these cocci that the material gets its name.
But cocciopesto is not the only material that could characterise the aqueduct as Roman. Layers of Vitruvian wall coverings with an upper ‘politones’ layer of finely ground marble would be just as convincing, as would standard sized Roman bricks or Opus Reticulatum.
The proof of whether the water conduit from Pimonte to Quisisana (near Pompeii and Sorrento) is ancient will probably rely on the identification of Roman building materials.
If these are discovered it will be interesting to see whether they can be interpreted as contemporary with materials used in the Serino aqueduct, or whether, perhaps, the materials are completely different.
We will wait to see what the explorers come up with: so far we believe they may have photographed some typical cocciopesto but the photographs are currently (3 January 2021) inaccessible due to Covid-19 restrictions.