Galvanic Corrosion is a type of corrosion that can happen to bronze sculptures that are electroplated. This was a method developed in the 19th century where a cheaper metal could be used to make up the form of a sculpture. A thin layer of brass or bronze would be added to give the aesthetic of a traditionally made item.
Galvanic corrosion occurs when the upper layer of the statue is nobler than the metal in the underlayer. If the upper layer comes under attack by something corrosive, or is porous, the less noble metal will begin to corrode preferentially.
In this situation, the bronze or brass provides a large cathodic area. Any small areas where the surface is compromised enables the anodic half-reaction to occur resulting in a large pit.
If the corrosion occurs beneath the bronze or brass surface, then the expansion of the corrosion products lifts the upper layer and detach it.
Recently we had a sculpture come in with just this issue. The underlying alloy was an iron-mixture plated with brass. When something corrosive splashed across it, the sculpture’s brass skin began to corrode in tiny areas. Once the upper layer was compromised, it began to rust below the surface. Soon the rust pushed through until there was a raised corrosion product in place. These small acne-like spots were spread all over the surface making the beautiful form of the sculpture highly disfigured.
If you’d like to learn more about corrosion and principles of bronze conservation, take a look at our online course, Bronze Behaving Badly.
Another good resource is Lyndsie Selwyn’s Book, Metals and Corrrosion
Founding Director Antique Bronze Ltd
John Branch, founding Director of Antique Bronze Ltd, died on 22nd December 2016 aged 86.
As a very young child, he showed an aptitude for gymnastics, a talent for art and a gift for entrepreneurship. However, it was during his national service that all these talents matured. The army encouraged and trained him in gymnastics, long-jump, boxing and sprinting. Achieving officer status as a PTI, he qualified for the Olympics in three disciplines while running an unofficial tailoring business for the soldiers.
It was while stationed in Cairo that John Branch first considered a career in restoration. Target practice on the Great Sphinx of Giza and the pyramids was a routine way to pass the time for the troops in 1948. The first time he witnessed this activity, he said,
He felt as if something close to murder was taking place.
He had no real understanding of their meaning or significance at the time, but he felt that this kind of vandalism was deeply wrong. This experience paved the way for a career as a carer of objects.
Upon returning to the UK, he enrolled in St Martin’s School of Art to study sculpture and afterwards worked for several noteworthy foundries including Morris Singers.
Though Antique Bronze wasn’t his only business, it was the one that maintained his interest life-long. Setting it up in 1955, John Branch carved out a career focusing on restoration of large-scale sculpture and historic buildings standing out among other restorers with his one-handed handstands on top of many of London’s best-known monuments. In particular, he became well-known by contemporary artists for his skills in patination.
Barbara Hepworth was a friend, and he went on to work on many other of our best-known artworks including those by Henry Moore’s, Frank Dobson, and a list of monuments including Nelson’s Column, The Albert Memorial, Cleopatras Needle, Eros among many others. He advised on The Preservation of Venice Project and was invited to move to New York for two years to consult on works to The Statue of Liberty.
Historic buildings such as County Hall, Royal Festival Hall, Senate House – The University of London Headquarters were also places where he invested much of his restoration talent. The complexity of some of the items he restored was unimaginable, and this is where his real gift was unsurpassed.
He trained and mentored many other craftsmen during his lifetime. Many were so devoted to him that they worked with him for the duration of their lives and left their sons to continue within the company. His love of art, breadth of restoration knowledge and generosity were so inspiring that most who met him were in awe of all he could do.
Caring for bronze sculpture in your home is much easier than those in your garden. Indoor bronzes have an easy time of it compared to their large companions outdoors. They are sheltered from the urban air and ever-changing weather, but their environment still has an impact on them and if you want to keep your small bronzes as stable as possible then consider these ten tips.
1: Dust Regularly – Don’t be frightened to touch a bronze just because it’s an artwork. If you use a dry micro-fibre cloth or a soft brush, you’ll be doing a lot of good rather than harm. Caring for bronze involves removing dirt and grime. This prevents reactions between the pollutants in dust and the metal’s surface. We all hate more housework, but preventing corrosion is always better than curing it.
2: At least once a year, give the statue a thorough clean. Use white spirit to remove dirt and grime – I use a cotton rag to apply it. Then put a protective coating in place – this is one of the best ways of protecting a bronze’s surface. Outdoor pollutants from traffic do infiltrate buildings. Over time, they will corrode your bronzes (Grontoft et al, 2016). Rub on microcrystalline wax and burnish with a bristle brush or cotton rag as you might your shoes. It will improve the bronze’s lustre and retard surface change.
3: Internal materials like wooden floorboards and furniture emit acidic gases such as acetic or formic acid. These will damage your bronzes particularly if airflow is static and if the temperature of a room is likely to fluctuate widely. To care for your bronze sculpture, consider where you locate your small bronzes. Try not to display them in sealed cabinets made from materials containing hard and soft woods or plywood (Gibson, 2010)
Care For Bronze Statues by Not Touching Them
4: Avoid handling your bronzes. If possible, lift your bronzes with a clean cloth rather than touch them directly. Sweat from the hands is acidic and will corrode metal. Wax is only a thin barrier layer.
5: If you are storing a small bronze rather than displaying it. Ensure that the packaging materials are suitable. Do not wrap bronzes directly in bubble wrap or plastic. Houses tend to have poor humidity controls and though it might surprise you – bronzes do hold water. When they heat up that water will evaporate and if you’ve trapped it in plastic – you’ll get corrosion activity beneath the plastic.
6: If you accidentally spill red wine, tea, coke or even water on your bronze – then run for a cloth! Just because it’s not a textile that stains – don’t assume that the liquid won’t do any harm. If you whip it off quickly, then harm is averted. If you leave it to dry out, the metal is likely to etch in the perfect shape of the splash or spill. A little warm water on a clean cloth as dry as possible will enable you to remove the liquid and save your bronze surface. Don’t forget to dry your bronze after you’ve washed it though – that’s very important.
7: Admire your bronze often – don’t ignore it. If you keep an eye on your sculpture, you will notice if there is any change occurring. If rapid change occurs within a short period, then the chances are it is being exposed to something. Be mindful, and you could prevent a bigger conservation problem.
The owner of this bronze noticed the surface was pitting
8: Think about where you locate your bronze. If a statue is in a busy area of the house, it might get knocked, and scuffed. Bronze looks tough, but often small bronzes have delicate sculptural detail, and one bang can see sections break off or snap. Dents are very hard to remove successfully. Drafts also carry outdoor pollutants inside and humidity will peak and trough more which won’t do your bronzes any good.
9: If you want to give your bronze the Rolls Royce treatment then a high-spec display case made with materials that do not emit gases will go a long way. Though undoubtedly an expense, it has been shown that cases with robust seals prevent traffic pollution getting in, provides extra security if you are burgled, prevents household damage like spills and knocks. A low and stable relative humidity under 40% is ideal. It’s also wise to add some activated carbon to the base of the case to absorb any stray pollutants.
10: If you notice a greenish, powdery deposit on your bronze which is easily brushed away, but returns quickly – get it to a conservator ASAP! This deposit is a sign of active corrosion and needs quick, skilled treatment to prevent metal loss.
If you would like help or advice on caring for your bronze statues, do give Antique Bronze Ltd a call on 0208 340 0931 or take a look at our small bronze restoration page
Terje Grontoft, David Thickett, Paul Lankester, Stephen Hackney, Joyce H. Townsend, Kristin Ramsholt & Monica Garrido. “Assessment of Indoor Air Quality and the Risk of Damage to Cultural Heritage Objects using MEMORI dosimetry” Studies in Conservation 61:sup 1, 70-82. Routledge & IIC 2016 Link Here
Gibson, L.T. (2010) Acetic and formic acids emitted from wood samples and their effect on selected materials in museum environments. Corrosion Science, 52 (1). pp. 172-178. ISSN 0010-938X
How To Clean a Bronze Sculpture
Recently, we had an enquiry from the archivist at Pembroke College, Oxford – Amanda Ingram about how to clean a bronze sculpture.
The college had rather a splendid bronze bust which had, unfortunately, been languishing in a basement for some time. It was to be relocated to a prominent position in the college, but it had to be cleaned. Amanda came to us for advice.
I have given it a light wipe with distilled water to remove surface dust but there is quite a lot of it which has a kind of fine crust on the surface. It is as if someone has wiped it with a dirty rag (for example containing paint residue) and this has set on the surface. The other thing is that it looks like parcel tape or something has, at some point, been stuck on his face and has, likewise, left a hard adhesive residue.
Our first suggestion was to try a solvent like acetone to remove the parcel tape residue and this worked extremely effectively. The rest that follows relates only to the dirt. Regarding the wiped, crusty areas we recommended trying to clean with some soap and water. If it worked, then to apply a couple of coats of micro-crystalline wax to the surface for protection. We suggested trying a small patch first and look at the outcome before going too far.
“Is nail varnish remover a suitable acetone or does it need to be a purer version? And, what sort of soap is best to use?”
Our advice was to buy a pure acetone as nail varnish remover often has added components. Although neutral soap solution is always a safe bet, when cleaning a bronze sculpture; it can be ineffective at cleaning stubborn dirt. This means more rubbing of the bronze’s surface is necessary which isn’t a good idea. Diluted Vulpex soap is slightly alkaline, but providing it is properly removed, can be a gentler method.
Amanda returned a short while later reporting that unfortunately, the dirt was still stubbornly in place.
Our advice was to try a little abrasion with something very fine. Just to do a very small area at the start with something like a very fine bronze wool and that this could be used with a little soap solution.
Amanda’s results speak for themselves. She applied Renaissance Micro-Crystalline wax after for the statue’s protection. Her careful approach has yielded some great results. Well done, Amanda!
Read about the surprising things that have happened to one of our Directors, Lucy Branch, in Diary of a Conservator published in World of Interiors August 2015. Beautiful illustration by Hannah Waldron.
Restoration Comedy by Lucy Branch, Published by World of Interiors, August 2015
You need a sense of humour to do my job. As a conservator of public art, I have the privilege of helping statues and monuments survive into the future. What could be so ridiculous about such a seemingly serious job? The objects I work on are high-profile and cannot be removed to the private enclave of a conservation studio. My studio is in the public domain and it’s very hard to control or predict that environment. What this means is that my working day might involve being up to my elbows in water while treating a sculpture in the Beatty and Jellicoe fountains in Trafalgar Square, or courted by a thousand tourists who would like their photos taken with the restorer at The Tower of London, or even finding a news crew up my ladder, while working on Shakespeare in Leicester Square, who wanted to know my opinion on Bill Clinton and Monica Lewinsky. One morning, I went to work on Eros to find a man dressed up as a dog had got there first.
Just before the most recent Royal Wedding, I worked on the gargantuan bronze elements of The Queen Victoria Memorial outside Buckingham Palace. This project was a joy and not just because we were required to down tools and watch the Changing of the Guard each day. The project began weeks before we started on site by looking at the history of the object. This aspect of the work involves dedicated research from published and unpublished documents and photographs. The aim is to try to ensure we know as much about how the object and what how it originally looked as possible.
Once the scaffold went up, it was time to meet the magnificent allegorical sculptures in person and get to grips with establishing their true condition. This might seem belated, but when tendering we don’t have the luxury of a scaffold so it is experience and a good pair of binoculars which are relied upon to anticipate what work will need to be done. Up close, it was evident that their surfaces had been coated comprehensively in a thick-pigmented wax containing a lot of lamp-black probably to hide the extensive disfiguring corrosion that was rampant below it. There was very little of the original patina to be found. Samples were taken for analysis, and we compared what we found from the physical evidence with what we found in the historic record.
It was quite something to stand next to those giant bronzes. They are truly otherworldly and above the pettiness of humans. They represent noble themes: peace, progress, agriculture and manufacture and with one hand upon the shoulder of Manufacture, I was a little awed at the extent of work that needed to be done so that they might be ready in time for their role on the world stage.
Before the physical work began, an accurate methodology and plan was devised. Due consideration was given to how far to intervene and what implications to the object certain treatments might have. This ethics stage of our work has come about through the damage done to historic objects, particularly between the 1930’s and 1950’s, in the name of restoration – the tragedy of the Elgin marbles must never be repeated. Only then did the craft aspect of the work begin. Failed wax layers were removed by steam and soap, corrosion layers thinned and treated, re-patination of the bronze where the original patina had been lost and copious layers of hot wax applied to protect the surface for the future.
I’d like to say my lasting memory of the project was seeing how wonderful the statues looked when the euphoric throng of people engulfed the monument on the big day, but actually being almost arrested for trying to blow up Buckingham Palace when one of our hired generator’s exploded will probably never be forgotten.