| 7 January 2021
How to mend a giant menhir
Struck by lightning in 1947, the giant menhir of Kerzerho in Erdeven (Morbihan, France), which threatened to split into several blocks, has been consolidated in an unprecedented rescue operation. The stone is part of Neolithic alignments 8 kilometres northwest of Carnac, in southern Brittany.
Two local sculptors specialised in the restoration of stones - Solen Moreau et Emmanuel Bertrand, who had previously been called in to clean graffiti from menhirs - were trusted with the work.
"It's not like a cathedral," says Solen Moreau. "You can't change the whole stone. You don't touch the outside." He does not seem bothered at the idea of repairing this ancient granite giant, more than 3.50 metres tall.
Scaffolding was erected around the menhir. Straps secured the weakened blocks. The cracks will always be seen. Eight cylindrical holes 32 millimetres in diameter are made at different levels of the menhir using a water-cooled diamond-coated drill bit - no vibration, and no risk of further damage, but eight hours to drill one metre. A metre-long 30 millimetre diameter brass rod weighing about 11 kilos is then inserted into each hole to stabilise the cracks. Brass was chosen for its durability and hold over time. The entrance holes are sealed with lime - no glue or resin, which can migrate into the stone. In 2,000 years, it will still be there, says Solen Moreau.
The entire publicly-funded operation costs about 10,000 euros. "This is probably a world first," says Laure d'Hauteville, conservator of the monument. Scientists specialising in Stonehenge, Galicia and Easter Island are interested in this restoration.
Edited from Ouest France (26 December 2020)
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