Webinar on 'Conservation of Architectural Metalwork – Part 1'

Conservation of Architectural Metalwork – Part 1 

Speakers: Rupert Harris and Sophie Godfraind 

Alice [00:03] Session on conservation of architectural metal work - part 1. Over to you, Sophie. 

Sophie [00:12] Thank you, Alice. Well, hello. Good afternoon, everyone, and thank you for joining us on this very sunny afternoon. Like Alice said, this is the first instalment we're running today on the very wide-ranging topic that is conservation of architectural metal work. So we will be introducing the general principles and approaches. My name is Sophie [last name?]. I work as a building conservation advisor in technical conservation. For anyone who might be new today – Sorry, I was trying to change the slide – Technical Conservation Team is a group of technical specialists, including conservators, engineers, building services engineers and geospatial surveyors. You can see two links on this slide that will give you access to our guidance document and all our technical advice freely available on our Web pages. We are very happy to have Rupert Harris back with us today. Rupert, would you like to introduce yourself? 

Rupert [01:30] Yes, hello everyone. My name is Rupert Harris. I'm a conservator and I specialise in metals primarily, and I not only act as a consultant for Historic England but care for the metalwork for National Trust and other bodies. And so my primary goal today is to try and walk you through very rapidly this very extensive subject of architectural metals. 

Alice [02:11] Sophie, you're still on mute. If you could just unmute your mic. 

Sophie [02:18] So this is Rupert. Over to you, Rupert. 

Rupert [02:22] So, I'm just going to-- Sorry about the delay there. I'm just going to-- This is just the slide just to indicate the sort of things we're talking about. You've got the Stratford cinema – Belsay brass cast and turn brass balustrading, [weave thorp?] internal metalwork; little slide of The Albert Memorial – very mixed and complex object; and the inside of the De La Warr Pavilion. This just covers a little snippet of what we're going to be talking about today. Sophie's probably just going to introduce ferrous metals and non-ferrous metals, which is what we'll be talking about, and then I'll come back in with some more examples. 

Sophie [03:13] That's right. Thank you, Rupert. So metals are divided in two main groups, like Rupert said, the ferrous and non-ferrous metal ones. Ferrous metals include wrought iron, cast iron, mild steel and stainless steel. Traditionally, iron and steel were used to wear strength. Resistance to wear and resistance to heat were the main requirement. But as you know, their main drawback was their susceptibility to corrosion. Then on the other hand, we have non-ferrous metals, which presented the advantage of their resistance to corrosion and malleability. They include lead, copper and its alloys, zinc, aluminium and tin. The rest of this presentation will follow broadly the same sequence, so we'll cover first ferrous and non-ferrous metals, then mixed metals. Back to you, Rupert. 

Rupert [04:16] So here we have an example of the Golden Gates at Burghley House. These are extraordinary gates. They're very early; they're [indistinct?]. And the reason I'm showing this really is for several reasons. The ironwork itself and these gates were restored not that long ago. They're interesting because the house was bomb damaged by a rogue dropping of a bomb during the Second World War, and the gates were restored. The owner of the house at the time happened to be involved in the aluminium industry, and a lot of the repoussé leaves on these gates are, in fact, aluminium. 

There are two things to mention here. One is that it is being decided these gates are due for the conservation workshop. It's been decided to keep the aluminium leaves as part of the history of the object. This might not necessarily be the case in many circumstances, but because of the history behind these, that's the decision that's going to be made. But the slide on the right really shows the problems that are associated with the lack of adequate preparation of the metalwork, particularly the priming and the undercoating before you apply the gold. Gold-leafing of this standing and properly prepared really should last for many, many years without this problem of rust-spotting and corrosion. So this really comes down to the fact that we have to look very carefully at the specifications for conservation, and it's something that's absolutely crucial in terms of cost, particularly. 

Another example of time passing is this rather wonderful [avery?] at Dropmore House. The slide on the right shows its condition currently – well, actually when I saw it not that long ago. And the slide on the left shows it in its former glory, and it's a mixture of wrought iron, cast iron and [wirework?], with panels of Chinese glazed ceramic, so it's a very complex object. A lot of the things-- You see probably quite clearly that the square decorations are almost completely missing from the image on the right, and there is a plan to redo it. But the most critical thing to look at here is the importance of research prior to doing any work, and that's where the understanding of how to research correctly and really going back into depth of house records, early photographs and everything else plays such a crucial role in conservation of pretty much every object, to be honest. 

Here's a slide showing the problems-- 

Sophie [07:14] Iron corrosion. 

Rupert [07:16] Mm. Iron corrosion and Sophie can mention-- 

Sophie [07:19] Yes, that's right. Yes, iron corrosion and its effects here on wrought iron, so it can look particularly dramatic because of its [laminate?] structure. From left to right, we see distortion, gradual loss of material and [spooling?] of the stone where the embedded iron cramps are located was in the stone. Iron corrosion involves some expansion in volume. Rust can be as much as seven times bigger in size, so it causes rust jacking. To protect the metal from corrosion, all historic ironwork was originally coated. Traditionally that would've been done using lead paint. Contrary to the perception we might have today, or even the expectation to see metal painted black, in fact black paint became ubiquitous on metal only from the 1960s onwards. Before that, there has been a whole history of changing fashions, including lead colour blue, green or red, and you can see that in the paint stratigraphy at the bottom right-hand side, with all the different successive layers of decoration. It's interesting to note as well that based on the analysis of external ironwork, we gauge that the repainting would have taken place about every seven years. And back to Rupert. 

Rupert [09:11] Just following what Sophie's just been saying, these are two examples of quite early work. You've got the Davis Brothers gates at Chirk Castle, and they are now painted an off-white stone colour, which is in fact the colour that they were originally painted. A lot of people don't understand this. They look at them and they think it's undercoat, but in fact, that's as they were originally made and decorated. On the right-hand side, this is West Front Staircase at Osterley, designed by Robert Adam, and these are very, very important metalwork sections and in detail they have a bronze handrail. And in these areas here the leaves, the rams’ heads and these little roundels are all, in fact, cast in bronze. And when this was originally decorated and we did a major extensive search for original paint, we were unable to find any on these particular bannisters. But luckily en suite with the staircase are two boot scrapers, which we managed to find the paint samples on your left-hand side, and these clearly show – rather like the Chirk [indistinct] – they were painted, originally, in stone-coloured paints, and the rams heads that I was indicating before and the leaf detail and these roundels were all leaf-gilded, and it's quite on ironwork, particularly where you find bronze detail, that that will indicate to you that it was originally going to be leaf-gilded. It was a preferable material to put leaf-gilding onto, rather than iron, and I suppose that's demonstrated by the problems and Burghley House Gates that I showed you earlier. 

Rupert [11:05] Following on from this and probably more to do with the issues of research, this is Kilmainham Gaol in Dublin, and it's a 19th-century building built in the 1860s. And the most important thing here was the roof, and the image on the left-hand side, you can see the skylight at the top has circular- or semi-circular-arched [panel?]. These are, in fact, plastic, and they're steel [ribs?] and polycarbonate lights, and clearly this is the historic image on your right-hand side, which clearly shows that the original roof had very tight glazing bars, and the restoration was looking at how do we work out not only how the glazing bars were put in, what the glass was that was put in them, but also most critically in some ways, was to get the visual look of this correct. And what was the original spacing? Nothing exists of the original at all, so we weren't able to work out easily how many glazing bars there would've been. We tried to count them but even an historic image is not very easy. And this involved a lot of research, and we looked at redesigning the glazing roof to be like it is originally, and that involved us in looking at the glass and also the design of the glazing bars. And we redeveloped new glazing bars that matched as close as we could the design of the originals, and there are close-up historic images of these, which we used as some source material. And unlike the original, because of health and safety issues with standard glass, we've used single-glass panes, or rungs of glass and toughened glass in this case, and this is the new roof in its old style being put back on. 

This slide really demonstrates – and I suppose it's the most critical thing really – that how quickly things can deteriorate. The image on your right-hand side is photographs taken in 1965 of the same gates, and these are Chevington gates from Ickworth House. The stone piers no longer exist. The gates partially exist, that are in a stall, and the two images on your left-hand side show the condition of the cast ironwork as it is now, and we are just about to start a project to try and work out how we can best restore the gates to some semblance of their former glory. But the damage, as you can see, to the cast iron is significant, and I suspect rather than repair in this instance, we may be looking at putting these back together and making new patterns and actually casting certainly the side panels in new iron. 

Following on from that, the several different varieties of cast ironwork. On the left-hand side, this is the rather important Brunel footbridge in Sydney Gardens in Bath. One of the problems in this photograph-- Luckily, the bridge still looks the same now. There was a plan. There was a plan to electrify the line between Bristol and Bath, which would've involved modifying quite significantly this bridge and raising the handrail by a metre to prevent people dropping things onto the electric cables, and a lot of research was looking into to work out how the bridge was assembled, which involved internal inspection of this piece here and whether or not we could raise the balustrade or how we would get around visually changing the bridge as little as possible while still retaining Brunel's design. But luckily, by sheer chance, money ran out and the project's been shelved for the time being, so the bridge still survives in its original Brunel condition. 

The middle fountain is a drinking fountain, and this is an image really to show you two things really. One is that in the centre of this structure, there used to be quite an elaborate drinking fountain, which was removed and disposed of because it was obscuring traffic view, and I suppose this demonstrates that nothing is set in terms of time. Things alter all the time. And the other thing about this is that the paint colours, I think, were probably designed by the local council. They are incorrect for the period. The use of silver paint was certainly not something that was used in the 19th century, so there again I suspect that no paint samples were taken, and it's purely a whim we're looking at here, the decorating for this particular element. 

And last but not least is the rather wonderful [Holborn?] Viaduct – granite columns with cast-iron spans and gilded bronze capitals. This mainly requires regular maintenance, and we'll come onto the issue of maintenance in a moment, but it's a very interesting mixed material and rather beautifully designed construction. The reason we're showing this image is two-fold. One is the rather wonderful, original cast iron lighting columns from the Brighton seafront. There are several things that have happened here over the years. First of all, due to lack of maintenance, and you can quite see in a coastal environment why this could be potentially a problem with multiple-section cast-iron columns of this size, and this rather strange bracket, which is show here in this top image, is a stainless-steel addition, which is being designed to hold the top lighting bracket in place to stop it falling off. And several attempts have been made to restore these, which have failed and consequently this is why the solution of putting the stainless-steel bracket came about. 

The other thing you notice is that the lanterns are falling off, and the reason that they're falling off is they decided to remake the lanterns in a different material, and corrosion attacked the material, and the lanterns are now plummeting to earth on a slightly regular basis. To reduce the weight of this element, which is heavy in terms of cast iron and socketed into the main column, the conception was that making it and casting these again, but using aluminium, would've been one solution. And the bottom image demonstrates what happens when you put cast iron and aluminium together in a coastal environment and don't protect it adequately, that the aluminium corrodes massively, and the same problem occurred; they just fell off. So this is a process that's still in practice, and a solution, hopefully, will be found, but really the key point about this whole project – and there are over 100 of these lighting columns – is the issue of maintenance. Had these been maintained correctly during their lifetime, none of this work – the brackets, the use of aluminium, all the failing joints in various sections of the columns – would not have been necessary or happened, so we're down to the issue of maintenance. 

And I suppose it's worth just halting here just briefly to talk about what it is that conservators and architects and surveyors need to know about objects, and the key thing really is to understand the history, how best to undertake very detailed research, how to identify risk in particular, have a very good depth of knowledge in your particular material specialisation and processes of deterioration and damage that those materials may suffer and methods used, whether they're scientific methods or visual methods, for assessment and investigation and also have a very good working knowledge of common and associated materials, because metals are attached to pretty much every other material you can possibly think of, from ceramics and glass to wood to stone and terracotta, so you have to, as if you're involved in the conservation of architecture and metals particularly, have a very good working knowledge of those other things. 

And I suppose last and perhaps not least are understanding what techniques you can use for repair and very much the principles and practice involved in the maintenance. An example of this is the cast-iron balusters at Castle Ward. These potentially date from the 1770s, perhaps 1780s. We're not absolutely sure. There's lots of historic research going on, looking at watercolours and paintings and documentary evidence in terms of writing and house records, but what is happening here is the grey cast iron in which these balusters were caused is brittle, as you can see by the bottom two images on the right. What's happening is that these balusters are now falling out. The only thing that's holding them in place is the inside-- There's this image here. So that's the base of the baluster. That was held in place by a block of wood, and that was the only thing holding the baluster in its position, and of course, the wood has rotted, so all these balusters – and I think we've counted out of the 360 that exist – over 60% of them are now loose. And so something has to be done, and this one was the one that fell out, and it fell down, fortunately missing anyone on the ground. 

And the image on the right-hand side shows the rust jacking between the top capping of the baluster and the iron itself, and this was obviously originally just filled with water. Well, what's happening is it's now lifting the capping stones, and so there is a project now involving how do we resolve the health and safety issue primarily but retaining the original cast iron where we can and, where it's been badly damaged in the case of the one on the lower left, recasting where necessary. We're not going to cover today the processes of repair and/or remaking because it's too much to cover, but hopefully some of that will be covered in our webinar 2 in a few weeks' time. 

Sophie [23:28] Rupert, sorry to interrupt, but if you go back to the previous slide, this is the sort of project where you would be also collaborating with a stone conservator, isn't it? 

Rupert [23:40] Absolutely. A large number of these projects, in fact, involve-- it could be stone conservators, it could be timber conservators, it could be brickwork or anything, but we're frequently involved in collaborative working. And certainly, in this case, it cannot go ahead without that very close collaborating, and the issue of cost comes very much to play here because we have not only to close elements. The building, we have to lift very large sections of stone; we have to undertake the repair in redecoration and resecuring of the balusters, all of which has to be scheduled while hopefully the house itself remains open to the public; and scheduling that in line with the wish of the client and all the other potential conservators involved is an absolutely crucial part of the project and involves quite significant meetings and planning to make sure that it all happens to plan. And with a project of this nature, it will be phased over several years, I suspect. 

Following on from that, [indistinct] more cast iron, and we were talking about rust jacking earlier, and this is the cast-iron figure of Our Lady from Stoneyhurst College in the Lake District near Penrith. And you can see the image on the right-hand side, I think shows there's a whole section missing here, which has disappeared. In fact, it was an angel in there, and the image on the right shows clearly the rust jacking and the causing of the massive split in this [baseorb?], and when we came to look at this, there really wasn't much holding this together. In fact, it could've fallen at any time, so it was considered to be an object at risk, and although it's a listed structure, because of that list status, we were able to go and take it down quickly before it actually fell.  

And the next image shows the sort of size of the object we're talking about in its location, and so there again we're talking about access and cost and crane hire and scaffold and how you actually manage a project like this, and the thing, I suppose, to remember about this project and many of the others, that the cost of the conservation quite often is less than the cost of the access and the lifting equipment, and we'll come onto some other images that show that probably more clearly. 

Cast iron again. This is the 19th-century electricity sub-station in Wimbledon – very important for two reasons. One, there are very few of these surviving as a structure, but most importantly is the existence of the original transformer and electrical switch gear inside it. This is a very rare example of a late-19th century distribution, and so this project, although it primarily started with the issue of preserving the exterior, and there was some problems with the cracking of the cast iron and the doors and the hinges weren't working and everything else, but once we actually opened it up and we realised that there was this very, very important piece of industrial archaeology inside, the project itself is now doubled in size, and so probably more energy is going to be put into the conservation of the inside of this object than the exterior. And this was something that we only discovered once we managed to get the actual substation opened up. 

Sophie [27:50] You mentioned that the science museum followed that quite closely as well. 

Rupert [27:59] Absolutely. Yeah, when we discover things like this, if it becomes a rare survival of any type of industrial technology, we often involve all sorts of people, like museums and other people, who quite often hold very good records. It's quite surprising that the power companies actually don't really have much of this record any less. Most of this historic record and information is held in libraries and museums, so there again more research was required, and we established where this transform was made and by which company and pretty much how it works, so it was very useful in that sense. And that project is for next year, I think. 

We're now into copper, so we're into the non-ferrous area of work. I'm going to show this very briefly. This is the Royal Observatory, King's Observatory in Greenwich-- sorry, in Richmond. Built in 1769 by George III, looking at-- He wanted to look at transit of Venus, and so he had this observatory built, specifically for that exercise. And the whole of the top of this building-- The roof and the sides of the observatory are copper-clad and painted, and this is the original copper from the 18th century. It's gone through many periods of decoration. On the right-hand side, this is a timber moulding, and in fact, we discovered by doing the paint samples again that when this was absolutely first built, this timber was just varnished with no paint at all. Only the copper was painted. But the issue about this particular project was that the house has now been let – the building has now been let as a private dwelling – and the roof on which the observatory sits needed to be reclad in lead, and initially there was a consideration to take off the copper cladding off the sides of this so the lead roof could be made so it was completely waterproof. And fortunately, with a little bit of toing and froing on the conservation front and looking quite carefully at techniques available, we were able to come up with a solution to save the copper cladding and still install a new lead roof that didn't affect this grade 1 listed building. It didn’t affect the copper at all. 

Another strange copper object. This is the Tide Gauge Hut on Westminster Pier. There are a few of these in London. This is probably the best-known one – not a very big structure, but it contains the original 19th century gauge by which the rise and fall of the tide on the Thames was measured. But because of its location, it gets vandalised on a regular basis, and although not very clearly, you see, but the copper cladding has now been pulled off. This is a timber-framed copper sheet-clad object and it's very delicate. And one of the problems-- and this has not been restored yet. One of the problems here is it's a highly populated area, exceedingly difficult access, with the river on one side and public steps on the other, no convenient access for cranage. So the issue was, could this be restored in situ? And the answer is 'with great difficulty and very high cost'. So we are now trying to come up with a solution of how this object can be saved because it is now starting to deteriorate quite badly. But there again, access, cost of work and public interference are the things that are most concerned with a project like this. 

Following on, the access issue, clearly with weathervanes. This is a significant problem. Weathervane on the right from [Harrison Halls?]. The top and right images are the late 17th-century copper grasshopper weathervane from the Royal Exchange, and the only reason we were up there recently to look at this was because scaffolding was put up to restore and clean the stonework. Otherwise, there would be no opportunity to check the physical structure of the weathervane itself, nor check the gilding. And the most critical thing, there wasn't time to restore the actual gilding or the weathervane itself. It was considered to be structurally sound enough, although degraded, but the key point was to try and make sure it was structurally sound for something that's that high off the ground, and in fact, this element here in the middle photograph, where I've got the arrow, that is a very large three-section cast-iron column. It had been worked on several times before, which we discovered once we started to take it apart, but there were absolutely no records of what had happened to it or when work had happened to it. So we've redocumented it now. Luckily, it's sound, so it's now been put back and it is considered to be safe for the next 30 years or so, until such time the scaffolding is put back up. 

And last but not least, the copper roof and figure, which is a repoussé copper figure of victory on top of March Town Hall. This is a hundred feet off the ground, and the arm fell off the statue, and it's still off the statue because clearly putting the arm back on and remaking it – although it was a bit flattened by the time it had fallen to the ground – the cost of scaffolding for a building of this size and in that particular venue was ten times the cost of the actual conservation work required, so currently it's being left as it is, but as far as we're concerned we've looked at it quite carefully from the ground and as close as we can with good camera images and with drones to check that it's OK, and as far as we're concerned, although armless, it will survive. 

More weathervanes. This is Saint Jude's Church in Hampstead Garden Suburb, one of the tallest spires in London, designed by Edward Lutyens, and this weathervane actually did fall off. It fell down. It disappeared from this point into the car park below, fortunately missing the section of lead here, with a rotating copper cockerel and fish. That whole section above my arrow dropped off, and just that section of lead weighed 60 kilos. 

And this image on the top-right shows the condition of the copper and the lead when we got it off or recovered it from the car park. And the reason it got off: the wind got up and this iron dowel, which went through the copper and down through the roof, and you could see at this point here where the iron had completely corroded away to such a point where it had no strength at all, and in the high wind it just fell off. And this is one of the problems with all these objects at high level, is that the access to check their condition is very, very difficult, and you sort of have to trust that it's going to be OK. But frequently what happens is there's an accident and only by the time there's an accident, you realise that there's a problem. And in this case, we reassembled the original to some degree so we could see what it looked like, but it was so damaged and so split and so weathered that, in fact, a new copper weathervane we made, and it is due to be put back on the church at the moment. 

One just interesting story about this. This ball, which is-- It's a pine ball clad in lead. This was actually taken off by steeplejacks from this point upwards, and inside the lead ball we found four-time capsules with a signed business card from Edward Lutyens, his building surveyor, photographs of the building in partial in partial state of building from the base scaffolding to the nave roof and other things. So a lot of history was discovered by sheer chance of this object being damaged so severely. 

Lead work, which I'm not going to cover in great detail here, because hopefully there will be a future webinar somewhere down the line, specifically dealing with lead work and the issues related to it. Here we have the Boycott Pavilions at Stowe, with wonderful lead roofs, and some of you listening today will be familiar with the problem of what we call 'lead conversion staining', which is the creation of this dark staining of lead roofs, in particular, although it can happen to lead statuary as well. And this is caused, we think, by the conversion of the existing natural corrosion products on lead to lead dioxide, which happens to be this purply-brown colour, and it's quite odd that it tends to happen in country situations, rather than lead roofs in city, and we think it's caused by the change due to the clean air act, the massive reduction of the sulphur dioxide, which appeared to passivate the lead, and the increase in knots, gases and pollutants, which we think destabilises and causes this conversion. 

And the other thing on the right-hand side to talk about briefly is that a lot of lead statuary was polychromed, and here we're talking about primarily 18th-century lead. This is just a very small example of one of the bluecoat figures, which were heavily polychromed, not only in multiple colours but quite often with added gilded decoration as well. But as I said, we're hopefully going to cover this in much more detail in a future webinar. 

Sophie [39:31] And just to mention, Rupert, the lead staining, in fact, is very resilient as well, so it's mainly an aesthetic problem, isn't it? 

Rupert [39:42] Absolutely. The research we've done, the lead dioxide is very hard and very brittle and very thin, so as far as we're concerned, it's not doing any damage to lead itself, but it is, as Sophie said, it's an aesthetic problem. And certainly, on statuary and on several lead roofs, particularly things like the Boycott Pavilions, where it's very obviously seen. Obviously on church and cathedral roofs, quite often it's less obvious because the roofs are hard to see from any distance. But we don't think it's deleterious to the structure of the lead and doesn't cause any particular corrosion problems in terms of weakness. 

This is aluminium. So we're talking about the eagle from the old American embassy in Grosvenor Square. It's very big, as you can see by the image on the left-hand side. It's 12 metres wing span, and this image here, it is thought that when this was made, and it was made in New York and shipped over in sections and then assembled in the UK and then put on the embassy, that it was attempted to anodise this [skull's collar?], and you can see here these little aluminium – they are in fact aluminium – decorative [freezes?], which are quite gold in colour, and we think almost certainly that the eagle was intended to be a very bright gold colour, and preferably anodised. But for anyone who understands the anodising process, which requires dipping in [tanks?], will realise that dipping aluminium of this sort of size of a welded and rather sculptural condition, getting it clean enough and secure enough to be able to hold a secure anodised coating is almost impossible, so I think that this failed very rapidly and paint was then used to decorate it with, and in this case it was a metallic paint – metal-flake paint – and what has happened over the years, that the paint medium and the metal flakes have oxidised, so now the eagle is looking this rather muddy brown colour. 

And on this bottom-left image shows the condition of a lot of the aluminium, where the paint is coming off, a huge amount of aluminium oxide on the surface, and this is an extreme example of underfilm corrosion, where once the paint's surface breaks down, water penetrates under the paint, and corrosion continues, and so this project is going to involve the complete removal of all surface coatings and all the corrosion and the redecoration. And along with that, obviously with a piece of sculpture in the position that this is in, we had to make sure that the internal structure was such that it was safe to put back on the building, so we did internal video and camera inspection of the internal armature and discovered that, in fact, although there was some light surface corrosion on the inside that it was all welds and bolt fixings and other things were still in very sound condition. 

More issues of maintenance and access. Fountains are a particular problem for two reasons – clearly access but secondly the maintenance and cleaning and redecoration, if necessary, can be very problematic because you're surrounding with water that either contains fish or plant life that you need to protect. So the care and maintenance of things like this becomes even more critical, because you really don't want to get to a situation where you've got to undertake major restoration work and worry about the protection of the environmental areas around it. The Lichfield-- This is a cast-iron fountain, so originally painted in lead-based paints in polychrome colours. So really to deal with something like this, you have to take the paint off, so that either involves abrasive media or forms of chemical. There again having to protect the water. 

The central image is a copy of a very important renaissance fountain, [the original now and the VNA?], but this is a problem of limescale appearing on the bronze itself, and bronze loves limescale, or limescale loves bronze, so if you do not regularly maintain and wax the surface of bronzes, you get this very heavy build-up of robust limescale, which is exceedingly difficult to remove. 

And last but not least, this is the Diana Fountain in Bushy Park. Very important renaissance fountain. Figures by Le Sueur, Sir Charles I royal sculpture. And on a Robert Adams – in this case – plinth, there was a scaffold walkway built to get access to this, so a hundred metres of scaffold walkway, and then the whole object was fully scaffolded to hopefully protect it and [cheat?] it. And this case, we have patinated bronzes, so their chemical patination with wax protection, and leaf-gilded bronze on the top. But the real point about this is access and environmental protection and cost. Not too bad with the other two, but the cost for the Diana Fountain was significant in terms of access. 

Sophie [46:03] Rupert, regarding the fountain, there are also examples where the use of chlorinated water activates the corrosion even faster? 

Rupert [46:16] Yeah, hopefully-- Well, certainly in the examples that I've just shown you, they don't suffer from chlorinated water problems, but certainly with a lot of fountains within buildings or city environments, where there is perceived to be a health and safety issue for water that is not clean, they do put chlorinated water through the systems, and of course, chlorine and metals of any sort really don't like one another at all, and you can end up with massive corrosion problems if you don't undertake very regular maintenance. Chlorine rapidly attacks metals, and really, it's a problem which you just have to deal with, and anyone who commissions, and it tends to be modern fountains fortunately. But anyone who commissions modern fountains needs to think very carefully about the cost of maintenance long-term and perhaps what materials they make them from in the first instance. 

This issue, moving to internal metalwork, this is the state dining room at Apsley House. There was a concern that the laylights in the ceiling of the banqueting hall were unstable, and these are glazed lights, and so we had internal scaffolding put up to look at the condition of what were considered at that point to be the glazing bars. And clearly, as you can see here and here, there are fractures in those, and there was a major concern that the engraved glass panels that fit into the light were only held in using what turns out to be painted brass sleeving with some putty. And in fact, so we were looking to see whether or not this was safe or not. So first of all, we did that inspection from the inside of the building, and then we went into the roof space – so the image on the right-hand side – and luckily with gave us much more confidence, we discovered that there's a very robust wrought-iron frame with the glass set into very well-puttied recesses. And the brass decoration was purely decorative to cover up the what-would-have-been a slightly ugly puttied joint from below. So the conclusion was, although this was visually not great when you look closely at it, they weren't going to drop off, they seemed to be quite stable and we assume that, in fact, it was caused by a little bit of substance in the building over time, so a few of these had come loose, but the overall assessment of the lights themselves were that they were absolutely stable, and we didn't need to consider a health and safety issue. 

Internal metalwork. I'm going to push on with this now because I know we're running short of time. Skidmore ironwork. So, we're inside here highly elaborate polychromed metal ironwork, absolute classic Skidmore work, with a lot of brass decoration. Can include lots of leaf gilding as well. Sadly, in many churches, this came out of fashion and some of them were removed. The Hereford Screen at the V&A is a classic example. But they do present quite a problem in terms of maintaining the original decoration. There are many, many examples around the country where these have been re-painted without proper research of the paint colours, and incorrectly, so there again research being very important. 

Back again to country-house technology to some degree. This is the yellow drawing room from Wimpole, and this is the rather wonderful late-19th century gaselier. So these little areas here on the right-hand image are the gas lights, and the whole thing, and this is a chimney running right up to a skylight, or a vent at the top. And we have gilt metal, steel, mica, heat-resistant cowling and then brass decoration and obviously glass pendants. So there again, it didn't look good, clearly hadn't been cleaned properly since it's been put up there and here again health and access, very difficult access. This is a seven-tier scaffold required to get to this object inside a highly important room, and there was an issue whether or not the chandelier glass elements were sound and safe. And so that was restrung, and the whole object was probably cleaned and reassembled and the glass rehung. But the scaffolding for this project alone was £20,000, which was more than the cost of the conservation work. 

Bridges. A huge problem because of the two things really. The materials – and this is why I showed you Vauxhall Bridge in the very first image of the subject – this is the steel work bridge built in the 1860s, replacing what was a cast iron bridge, which only survived 70 years, and so one of the issues about all this is that we live in a world of great transience and the ability for objects to survive is minimal, and they often don't last very long. And we're in an ever-changing world, and who knows how long Vauxhall Bridge will survive, because the cost of maintaining bridges – whether it be Hammersmith Bridge, Vauxhall Bridge, Black Friars Bridge, wherever they are – massive, and of course, the traffic hold-ups of dealing with them are extensive. One of the reasons for showing this is the bronze figures, which are rather wonderful. They're by Pomeroy and Frances Drury. They're four metres high and they weigh two tons each. Most people have never seen them before, and if anyone wants to have a quiz of where do you find a model of St Paul's in London, there it is. In this case, because of no access and the ability to look after the bronze, it's been painted to protect it. 

If you want to find a building that sums up all these issues of external metalwork in all its glory, Selfridges is a very good example. You have the Queen of Time clock, gilded and silvered bronze with mosaic and ceramic. These are cast-iron windows on the right-hand side, bronze decoration, pressed steel and glass, and also, it's the very first steel-frame building in the country. So Selfridges is a great example of architectural metals in one place to go and look at if you ever get the chance. 

Door furniture and [fiskings?] of fittings. The point I'm making here, because I'm not going to cover this in any great detail, is the recording of them. So often when there is a problem with houses disasters, information relating to these – what we call – small and perhaps insignificant items are lost. No one has photographed them, recorded them and know what they look like, and some of them can be absolutely important. The image on this right-hand side, this is a fantastic, pierced steel lock from Powys Castle in Wales, a 17th-century door locker on a church and ironwork holding windows in place, and going back to Sophie's issue, we've got issues of spalling of the stone due to rust jacking and protection. But all of this-- The point I'm making here, is record, record, record before you do anything. 

And last but not least, what happens when everything goes desperately wrong? And that's the point of recording, I suppose. This is the most recent fire at Clandon, and the house was lost. This is the entrance hall, there rather wonderful bracket lamps. There's one on the right-hand side still existing. In fact, they both survived and the house is going to be put back. This fire was caused by electrical problems in the basement, which spread to the roof, and then the house burned from the top down. And then we have Uppark, which is earlier. This is back into the late 1980s, caused by lead burning on the roof, so repair of the lead. It wasn't monitored adequately. There was a strong wind, the house caught fire and there again burned from the top down. 

And the image on the right, more disaster. So, the house was saved. The external part of the house was saved. The scaffolding was put up. Then we had a hurricane, and the hurricane then blew the scaffolding down and very sadly killed one person in the process. So even though when you've had a major disaster, other disasters can follow, and I suppose there again, it goes back to this issue of transience and the problem of saving stuff long term. 

And last but not least, other-- 

Sophie [56:49] Sorry, Rupert. Can I-- 

Rupert [56:52] Yes, Sophie. 

Sophie [56:53] Can I just return back to the fire, just to mention also the importance of heading an energy salvage plan in place, that has been covered, I think, by [Colize?] of the building services engineering team, where there is a plan for access to the firemen and to know where the objects to salvage are located so that in case of a disaster like this, one knows how to act really. You can find a link on our technical advice pages. 

Rupert [57:38] Yeah, it's absolutely crucially important. In fact, obviously these are National Trust properties, and National Trust are very, very high on their planning for salvage and everything else, and access, so it is covered. But obviously, there are many, many private residences where this may sadly happen in the future, and working out a salvage plan, knowing where to go, where the fire brigade can actually get access to the building, where they might [not to?], where there is enough water source are all crucial things to look at, and listing star objects and things like that are very important. So if the fire brigade turn up, you can actually get, hopefully, some of these objects out of the house before they disappear in smoke. 

On the right-- 

Sophie [58:24] And sticking to the health and safety rules as well, because a lot of those fires happen after hot works have taken place. 

Rupert [58:36] Well, monitoring site works is absolutely crucial. I mean, fortunately within architectural metals, apart from lead burning, it's not often that we have an issue where metals are going to be the source of the problem, but certainly with lead burning on roofs it is absolutely crucial that the health and safety assessment is undertaken and fire watches afterwards are carried out. Yeah, it's-- I don't think anyone would do it these days, hopefully not anyway, without going through that process. 

And then this, very lastly, this is the-- sadly Ickworth comes in for a bit of a banging really. This is a car that drove down a very straight drive and missed the gate completely and demolished the stone piers and the cast-iron railings. Unfortunately, the two [indistinct] occupants of the car, they happened to crash their building next to the lodge, where a profoundly deaf person lived, and so no one knew that the accident happened until half an hour afterwards. And the theft of sculpture and metalwork – whether it be lead of roofs or anything else like that – this is an attempted theft of a lead figure from [Southall?], where luckily the lead was too heavy to carry off. But they managed to demolish the plinth and do damage to the figure in the process. 

So that, I'm afraid, is a very, very rapid whizz through, and I've missed out so many things I'd loved to have said, but I hope that's given everyone attending some very brief glimpse of what we were talking about, and I hope that there might be some questions if everyone can stay, or those people that can stay, that we can deal with now. 

Alice [01:00:34] Thank you very much, Sophie and Rupert. We have a few questions from earlier. If anybody has any questions that they want to add to the chat, that's not a problem. It's a good time to do that. We have a few minutes, and if you'd like to stay with us, that would be great. So we had a question, Sophie and David, from Daniel [Cantrill?]. He was interested about the uses of sort of iron-painted versus bees’ wax finishing when we were talking about the painted ironwork railings at the beginning of the presentation. I don't know if you'd like to weigh in on that. I'm not quite sure what his question was. He did ask it a second time. He was wondering about ironwork such as door handles that have no sign of paint or probably hot bees’ wax finished, rather than changed by painting. So I'm not sure if his question is about using microcrystal and wax versus painting them. If you have any opinions on that, please weigh in. 

Rupert [01:01:29] Do you want to take that, Sophie. 

Sophie [01:01:37] Rupert, I was going to say for you, but we had a query about a bridge some time ago, whether there might be an option for using. But actually that was not bees’ wax. That was for the use of linseed oil instead of paint, whether that might be cheaper, but actually in that case it wouldn't have assured the protection of the metal for much longer either. There wasn't any advantage in that, to doing nothing. In terms of the door handles, I'm not sure, Rupert, is that something you have seen? 

Rupert [01:02:17] Well, in terms of door furniture and internal fixings made of iron or steel, generally speaking the key question is about ironwork, is whether or not the environment is good enough. If the environment is poor, then you're going to have a problem, in which case some protection is probably necessary. Generally speaking, if one looks at – take the National Trust, for instance – then we would use, if necessary, a very light coating of wax. But often we would leave it alone. Obviously, the perspiration from hands can cause corrosion, but we wouldn't out of choice put surface coatings particularly onto burnished or polished ironwork in properties themselves. But if you're going to, then a light coating of clear wax is perfectly adequate. We certainly wouldn't paint any type of internal ironwork like that that was not intended to be painted in the first instance. 

Do we have more questions, Alice? 

Alice [01:03:28] Apologies. I was on silent there. It actually leads onto [Karen Pritchards'?] query on-- Basically, she's asked for a comment on [ice?] being testing the use of linseed oil as a rust prohibitory. So you've kind of mentioned that already, Sophie, in the last question. So don't know if you have any further comments on that. 

Rupert [01:03:49] I do. 

Sophie [01:03:50] Not for my-- 

Rupert [01:03:54] On external ironwork, oil's, generally speaking, are not particularly good at preventing the penetration of moisture, and one of the problems of using something like boiled linseed oil, which does dry reasonably well, but certainly in any types of elevated temperatures, it becomes sticky and collects dirt and dust and is difficult to handle. And obviously, once you've painted something with an oil like that, it precludes completely the application of any type of future contemporary or even historic-type paint, because it just won't stick. So if you're going to use oil on external ironwork, then by all means use it and try it, but you have to understand that it's going to make it very difficult to apply any coatings in the future, should you choose to do so. 

Alice [01:04:47] We've just had an additional question from Robert Frostick. Do you have any advice on loosening cast-iron joints and structural connections which have rusted closed? Any lubricants or corrosion removal measures? 

Rupert [01:05:04] Right. Two things. Possibly penetrating oil first to see when you can break some of the rust down. Heat will probably do the job, whether it's wrought iron or cast iron, used carefully. Certainly, if it's cast-iron, then you want to hopefully warm and heat the whole object, and it will break down the rust to some degree. But it slightly depends on what the wrought or cast iron is attached to, whether or not you can actually safely do that. But the same process of using heat to break down rust scale is used in the cleaning and preparation of wrought-iron gates and railings quite frequently. So it is quite effective, but you've got to look very carefully whether or not there is risk to the object due to possible thermal cracking if it's cast iron or any types of other material that the wrought iron's attached to. So it has to be taken on a case-by-case basis. I would suggest that penetration to start with, followed by heat and perhaps a little bit of care and leverage is what you need to do, but it's not an easy thing to answer, and it has to be looked at, as I said, really on a case-by-case basis. 

Sophie [01:06:40] And you and Alex [Goode?] will cover that topic in more details as well in the part two of this session. Yes, I noticed, actually, Alex is one of the participants today, so hi, Alex, and I hope you've picked up some hints on what we've covered today for the next webinar. But yes, we will cover in much more detail, hopefully, the techniques for the treatment of ironwork generally, both cast and wrought. 

Alice [01:07:14] Will that include some elaboration on biometallic corrosion in the next seminar? 

Rupert [01:07:21] If necessary, yes. Absolutely, yeah, yeah. 

Alice [01:07:24] Because we have a question from Matthew [Wichrick?], which I think will be our last question for today. I've got two short ones after him. His question is an elaboration on biometallic corrosion, especially when it comes to fixings and cast iron. It would appear that many of the options available have drawbacks, and should these be chosen on a case-by-case basis? Which I think you've alluded to in previous conversations. 

Rupert [01:07:50] Yeah, the issue of biometallic corrosion between bronze alloys, for instance, copper alloys and ironwork would be a big problem. There has been a long tendency of introducing a tipping of railings and gates and other things into stonework using stainless steels. It can be done, but obviously with all ironwork, external ironwork, the surface coating that you put on it is the crucial thing. If you do not maintain the surface coatings, you will get some corrosion. But there is a reasonably limited amount of disastrous biometallic corrosion between stainless steels and iron if you use the correct welding rods to do the joint, or maybe a physical joint, whether it's nuts and bolts or rivets. But protection with surface coatings is the key for long-term maintenance. 

Alice [01:08:56] We have a short question. I'm not sure if you know the answer, but Adam Bent asks, 'Who made the gaselier?' Do we know? 

Rupert [01:09:01] Ah, we don't know. Unfortunately, it's not signed, nor stamped anywhere. There is some research trying to-- We think it might have actually been a special commission and designed for making gaslights, and it was specifically designed for the yellow drawing room at Wimpole only. But the trouble is that the burners, which you normally try and get the name from, they do have a name on them, but that doesn't necessarily mean they were the manufacturer of the gaselier itself, because they were a sort of off-the-shelf item. But if we find out, I'm sure Wimpole will have that information available. 

Sophie [01:09:48] And if I remember, you mentioned that the glass element was shredded with an iron thread, which is why you were worried that it might crack. 

Rupert [01:09:57] No, they're brass. They're very thin brass wire, and one of the problems with brass, particularly in environments where you have sulphurous gas, the wire can corrode and become quite brittle, and that's the problem with chandelier wires sometimes. And there is generally a rule that if access is provided, you use that opportunity to replace the wire just to be on the safe side. 

Alice [01:10:33] We have one last sneaky question from Adam. 'Rupert, have you come across hot linseed oil foundry seasoning of cast iron as a transport protection before painting. 

Rupert [01:10:43] Yes. Generally not used that much anymore because there are a whole load of modern plastic polymer-type coatings that can be sprayed on in film form, that you can peel off afterwards. And so generally speaking, because of the handling issue and the post-installation cleaning issues, the use of oils of any description, whether it be linseed oil or any type of mineral oil, is generally speaking out of fashion now. But it certainly used to be a process used right through the 19th century and 20th century-- early 20th century. So yes, I know about the process, but I think these days it's been superseded with other materials. 

Alice [01:11:37] And on that note, I think on that note, we are going to draw this technical Tuesday to a close. Thank you so much, Sophie--