Reprinted from HUB 19 September 2007
It's a little-known fact that Lord Byron, Jane Austen, Lord Palmerston and The Earl of Liverpool all used the same bottle bank in London.
To be more precise they used Hoares Bank, which was founded as a private deposit bank by Richard Hoare in 1672 at the sign of the Golden Bottle in Cheapside, London.
In 1690 the bank moved to new premises in Fleet Street, but continued to identify their premises by hanging a gilded leather bottle outside, at a time when street numbering was unknown.
In 1829 Charles Parker rebuilt the Fleet Street premises and the sign of the Golden Bottle was incorporated into the design of the façade to maintain the tradition.
C. Hoare & Co. is now the sole survivor of the private deposit banks that were established in the 17th and 18th centuries. It is as up to date as any other, and has even introduced a chip and pin technique to ensure that the appearance of the Grade II* listed façade continues to reflect the high quality of the service provided inside.
The problem that confronted the bank was that the original iron cramps used to tie the masonry façade together had started to corrode and cause the stone to fracture.
A typical construction detail in the early 1800s was that stones were tied together using iron straps known as ‘dog cramps'. The close proximity of the cramps to the face of the stone on the façade provided the ideal environment for them to corrode. As the cramps corroded they had the ability to expand between 7 - 12 times the size of the parent metal and this caused the stone to fracture.
The traditional method of repair would have involved the wholesale removal of the stone facing in order to locate the cramps. They would be replaced with stainless steel dog cramps and then new stone would be used to match the original stone.
A more ingenious and discreet method of repair was needed so that the bank could remain open for business at all times and PAYE Stonework and Restoration, a member of Stone Federation Great Britain, was called in to undertake the task.
The bank's technical advisors decided to locate the position of each of the dog cramps using x-ray mapping and then install a cathodic protection system to prevent further corrosion of the cramps.
Corrosion is an electro-chemical process that involves the passage of electrical currents between anodic and cathodic sites with corrosion usually occurring at the anodic sites.
An Impressed current cathodic protection system involves the application of a low voltage direct current from an inert anode material onto the steel cramps to make all the cramps cathodic, thus protecting them from further corrosion.
The first reported practical use of cathodic protection is generally credited to Sir Humphrey Davy in the 1820s. Davy's advice was sought by the Royal Navy in investigating the corrosion of copper sheeting used for cladding the hulls of naval vessels. Davy found that he could preserve copper in seawater by the attachment of small quantities of iron, zinc or tin. The copper became, as Davy put it, "cathodically protected."
The most rapid development of cathodic protection was made in the United States of America and by 1945, the method was well established to meet the requirements of the rapidly expanding oil and natural gas industry, which wanted to benefit from the advantages of using thin-walled steel pipes for underground transmission.
The use of this technology has been used extensively in the protection of steel framed masonry façades constructed in the early 1900's where the steel frame is relatively easy to locate and connect to.
The project at Hoares Bank was the first successful use of the technology to arrest the corrosion of isolated metal components (i.e not steel framed) embedded in a listed façade of a commercial premises in the United Kingdom. Every dog cramp had to be located and wired together with a titanium wire through a discreet hole in the face of the stone.
An anode was then installed in close proximity to each cramp and the system was completed once a low voltage direct current was placed through the system. The entire system is computer controlled and monitored remotely to ensure that it performs efficiently.
Where the stone had already fractured and failed, replacement stone was sourced which matched the original 1829 stone and carved to match seamlessly, including a fine tooling pattern to the face of the stone.
According to PAYE associate director Robert Greer "The end result is an effective method of corrosion protection to an important listed façade so discreet that all you see is the sign of the Golden Bottle as you walk by."
Jane Buxey, director of Stone Federation Great Britain, said, "It's another example of the quality of work undertaken by all members of the Stone Federation."