This month’s blog post comes from Jonathan Leburn, a Sculpture Conservator with Graciela Ainsworth Sculpture Conservation Ltd. He describes the recent treatment of a monumental statue in Edinburgh….
Moving sculptures is a large part the conservation work that we do, some sculptures however are larger than others.
Front and back of statue
We have recently finished the conservation of a 3 metre tall and over two ton in weight, bronze statue of William Chambers and 5 associated bronze plaques, as part of the revamp to create more public space outside the National Museum of Scotland.
The statue and plinth which date from 1891 have only been moved about 10 metres from their original position, however in order for the conservation works to be undertaken the sculpture and plaques needed to travel a little further.
The fixing methods of sculptures to their plinths is always somewhat of an unknown, and can often make removal of objects tricky. We will always try to remove the sculptures causing as little damage as possible to the original piece.
On this particular occasion it was clear that there were a number of doweled anchor points set into the stone from three footplates. These clearly couldn’t be removed without causing significant damage to the stonework, and as a result the next best option was to cut through the bronze footplates.
Before this could be done the sculpture was carefully slung and a hi-ab crane was brought in to take some of the sculptures weight and ensure that when the last of the fixings had been cut the sculpture would be secure and would not topple.
Cutting through the bronze footplates to free the sculpture
The sculpture was then carefully raised up off its plinth and over the scaffold, before being lowered onto the back of the hi-ab lorry.
The sculpture is lowered onto a large pallet with thick plastazote softening
Once back at our workshop the sculpture was initially placed in the workshop on his back. This allowed us to have a good look at the internals of the sculpture and with the aid of an endoscope we could view the condition of the bronze right the way up the sculpture. Structurally there did not appear to be any significant issues however it is often interesting to see what has been placed up the sculptures, in this case large amounts of twisted ferrous metal bars and stakes.
Ferrous metal found inside the sculpture
We removed the original fixings and the remainder of the footplates we had cut away from the top stone of the plinth by way of a core drill and then using a hammer and chisel to carefully shock off the remaining concrete attached to the dowels. Once removed it was clear to see the high workmanship of the original fixings that remarkably after all this time were still easily unscrewed from the footplates.
Original fixings having been removed from the top plinth stone
The cut away sections of the footplates were then welded back to their original positions and a new bronze pad was also welded to the underside of each of these footplates to give added strength. Threaded holes were drilled and cut into the new footplate sections to line up with the original holes and new stainless steel dowel was cut to fit into each of the footplates.
The depth of footprint was then increased on the plinth top by way of hammer and chisel to allow for the new bronze footplate sections that had been added. This ensured the sculpture would sit at the same height on the top stone.
Discreet pigmented wax tests were also undertaken at this time on the underside of the left foot to help us decide on the best colour option.
Carrying out wax tests
The sculpture was raised back to its vertical position by way of a tall gantry within the workshop and was then given a thorough washing down with potable water and nylon brushes. This was done to remove general dirt and bird guano present on the bronze surface.
Following this the bronze surface was again brushed, this time using copper brushes to enable removal of loose verdigris and sulphation crust from the surface of the bronze. Small areas of graffiti were also removed at this point using a combination of chemicals.
The bronze was treated with a chelating agent to inhibit against future corrosion to the surface. Following this it was gently heated with a propane torch to remove all moisture.
Considering its age the bronze was in a generally sound state, however there were areas that required attention. Specifically the top of the head was in a poor condition. Being that the head is the most likely spot for a bird to land and with the acidic nature of bird guano it is not uncommon to find that the tops of sculptures are generally in a poorer condition than the rest.
There was quite significant pitting to the head of Chambers that required filling with an epoxy resin. This was pigmented to match the colour of the surrounding bronze.
Top of head prior to filling
Filling the pitted surface with pigmented epoxy resin
Once all holes had been filled the bronze was again heated, this time to melt the first coat of pigmented wax into the metal surface. Following this first application the sculpture was left to cool down and allow the wax to harden. The wax was then buffed into the bronze to harden it further. A second application of wax was applied to the sculpture cold which again was buffed to harden. This process was repeated twice further in order to increase the layers of protection the wax gives the sculpture. It also increases the depth of colour to the sculpture as the pigmented wax layers build up.
Applying first coat of wax
Following completion of the conservation works the sculpture was transported back to the new site of the original plinth which itself had been dismantled, conserved and re-built.
To ensure the sculpture would be completely solid on top of its plinth a core drill was used to deepen each of the original holes that would receive the sculptures dowels. The holes were thus drilled down into the second stone from the top.
The sculpture was then lifted just above the plinth top so the dowels could be screwed up into the footplates. A dry run was then undertaken to ensure that all dowels and footplates fitted correctly into position. Following the successful dry run the sculpture was lifted back up and the holes in the top stone were filled with an epoxy grout. The sculpture was then lowered down into its final position.
Dowels being threaded into position prior to final positioning of sculpture
Final positioning of sculpture and plaques
Written by Jonathan Leburn Sculpture Conservator with Graciela Ainsworth Sculpture Conservation Ltd, Edinburgh.