Webinar on 'Conservation of Architectural Metalwork: Part 2 Iron Gates and Railings'

Conservation of Architectural Metalwork Part 2 – Iron Gates and Railings 

Speakers: Sophie Godfraind, Ruper Harris and Alex Coode 

Sophie [00:00] ...and I'm a building conservation advisor in technical conservation. For anyone who's new today, technical conservation team is a group of technical specialists, including conservators, engineers, building services engineers and geospatial surveyors. If you are interested, you can find a list of all our publications and access our technical advice on the links that you can see on the screen now. I'm delighted to welcome now our two guest speakers: Alex Coode and Rupert Harris. Alex, would you like to introduce yourself? 

Alex [00:54] Absolutely. My name's Alex Coode, originally trained as a blacksmith. I have a business entirely specialised in historic heritage work for the past eight years. 

Rupert [01:11] And I'm Rupert Harris. I'm a conservation advisor to National Trust and consultant on architectural metals for Historic England and a practising conservator. In-- We skipped an image. Go back one. I thought it'd be sensible to kick off, just to make sure that we all understand the materials we're talking about, which are significantly different, although they are both irons. We have the difference between the two is really between 3 and 4% of carbon in the alloy. Wrought iron, which is ductile and very tensile strength and has inclusions of slag, which is mainly silicones, which creates a fibrous microstructure, and there are two forms of iron, the wrought iron that we're talking about here today. One is charcoal iron, which is the early form, which is pre-1784, and from '74 onwards, we are talking about puddled iron, which was made in a reverberatory furnace, and clearly they're two very different materials. 

The cast iron has very high compressive strength but is brittle and is generally sand cast from patterns, which allows mass production of the same components over and over and over again, so that's why we see that. And to identify cast iron, often you will look for objects which have minimal undercuts, and certainly in the form of railings and gate piers and other items like that. You will find that the sides are very slightly tapered, and the tapering is there so that the iron can be pulled-- or the moulds can be pulled from the patterns without breaking them. Clearly the two different types of material have, because of their structural capabilities, are used for very different things, and obviously with the wrought iron, we have different types of assemblies. So wrought iron generally is joined by fire welding, riveted or pinned, and of course because it's wrought and it's wrought by a black smith by hand, each element is completely unique, whereas with cast iron, you have castings, which basically are-- should be almost identical time after time. 

The cast iron fabrication techniques are purely mechanical, so they're joined by screws and bolts and pins. They are not assembled by any form of welding in their original form that we're going to be talking about today. In terms of corrosion, the wrought iron tends to be really volumous, and for those of you who joined us last week and you'll see again today several examples of what we call rust jacking, very expansive forms of corrosion, whereas wrought iron tends to be really quite thin, and except in exceptional circumstances tends not to cause a structural problem. Where we have a structural problem, which we will come on today, is where wrought iron and cast iron are used in combination. And clearly because of the two different forms of strength of the material and different volumes of corrosion, this can significantly cause a problem with the corrosion and structural failure of elements like that. So that's a very, very, very brief overview of the two materials we're talking about. 

I'm going to show you first pictures of Tredegar House. These are very important gates, made by the Edney brothers of Bristol between 1714 and 1718. They were in exceedingly bad condition during the 19th century and right through to the 1950s, where they were partially dismantled for health and safety concerns. There was no restoration undertaken with these at all. In fact, in 1970s – and there may be someone from [Bridge?] Canals listening – Richard Cornell was asked to report and estimate for their restoration. No money was found, and it wasn't until the 1980s and again in 1996 that work was carried out. 

And I think it's important here to just briefly talk about the issues related to whether we consider these objects to be significant works of art and design, and if the answer is yes, then of course the principles of restoration need to be very, very carefully thought about, particularly in relation to the issues about replacement. And the reason that I'm showing these two images, this is a photograph on your right-hand side of the gates in 1908, and the image on your left is taken by me about seven years ago. And if one was to look at these – and I'll ask you to do this now – but if you were to look at them very closely, you'll see that not only are there a major design differences between the two, but there has been the addition of repoussé leaves and scrolls, which don't exist and never did exist on the photograph in 1908, and quite possibly before. 

There are obviously principles related to the conservation and restoration of all objects and particularly in this case wrought-iron and cast-iron railings and gates, and there aren't mountains of conservation principles in existence. Historic England's conservation principles, which are published in 2008, are very overarching conservation principles of all sorts of situations but will definitely pertain to ironwork. And then there are other bodies. The National Trust and others and the NHIG, who are now-- I think it's their tenth anniversary, who I've also published conservation principles for the repair and work to important historic ironwork. 

It's important, however, to be conscious that there are many factors to consider, and often pragmatism and compromise is necessary and that these considerations may override a more purist and prescriptive approach to the restoration. So although in ideal circumstances we might want to restore things very carefully using exactly the right materials and everything else, there are many, many factors, not least – which I've described in this case – finance. But I can't stress more the importance here of research, and had the two blacksmiths involved in the restoration of these in the '80s and '90s looked at the photograph of 1908, they would have clearly seen more information than perhaps they were able to deduce from the gates when they saw them. 

And I think it's important to discuss here and keep in mind what we consider to be original and what not, and we will cover this in various other examples, but one has to be very careful about the addition of leaves and scrolls and other decoration to historic gates and railings, because it's not necessarily the thing that should be done in my view, although I'm sure there will be many other views and questions flying in at some point or other about this. And obviously the issue here again of colour and gilding, and we will be talking about paint samples and other things later and the issues related to paint sampling and whether or not to use original historic colours or not, and quite often that is a matter – as we will see by the very fact that [paint-ons?] exist – that they're a matter of fashion over the years. 

Move on one. As an example partly of other problems, these are gates from Hartford Hall in Northumberland. These are grade 2 star listed gates and railings. They were removed in 2002 on the instruction of the owner, but unfortunately, no one enquired to whether or not they had listed building consent to remove them, and this caused a significant amount of trouble. They are Coalbrookdale, and they were actually exhibited in the Vienna exhibition in 1873 to a designer called Bruce James. And they are very, very important, and at the moment they are now – because of the legal issues related to the problem – they are now languishing [in store?], and there is a site trying to be found for them, but they are very, very significant. One of the issues – important to look at here – we have a combination of wrought and cast iron, and particularly in the lower right-hand image, the box sections are cast iron, but you have these very wonderful twists, which I can show you here and here. These are hugely important in terms of design and development. They made by-- Or the technique was developed by Stephen [Tuddenham?], and they're now [Tuddenham?] twists, and in fact, they are marked and he developed this system for making highly elaborate, beautifully constructed scroll work, and you can find this across the country, but you need to look carefully. But it's very interesting-- For those of you who are really interested, you can look it up and find out more about him. 

But obviously we have historic paint. These were originally maroon and gilded. The centre image shows it in its cleaned – all the paint is removed – and it now has-- it's just in its semi-rusted form, ready for future work. But at the moment, they are stuck in limbo, which is very unfortunate, but it is a warning to everyone if they're going to work on historic gates and railings and are asked to remove them to make sure that they are not covered by listed building consent. Otherwise, all sorts of problems transpire. 

All of you will be familiar, I think, with Hampton Court, and I suppose that this is an absolutely classic example of grade 1 listed gates and screens, by John Tijou, and they were constructed for William and Mary between 1689 and 1692, and the Privy Gardens of which they border the river were completed in 1702, and so they are highly significant pieces of-- Tijou was a Huguenot, as were many artisans who came over during the persecution to the UK at that period. They suffered massive neglect during the 18th and 19th century, and they were eventually completely removed in the 19th century. Well, I think in 1865 is what is recorded, and they were removed to the V&A, and bits of the repoussé work, in particular, were scattered about the country to various museums. And obviously since the restoration of the Privy Gardens and the return of the screens to Hampton Court, there has been a major, major process of conservation and restoration undertaken. 

And I suppose this follows on from the images I showed of Tredegar, where one has to consider, what are you restoring and how are you restoring it? We know certainly that at least 50% and possibly more of the repoussé work on these gates is not Tijou's work. It's the work-- or Tijou and his team of blacksmiths. And we know that a huge amount was recreated, so it's the point again that I'm making about what is original and what are we saving? Are we saving design only, or are we considering the repoussé work undertaken at the period it was made as being the most important? But these particular-- Because they're in such a prominent position, of course they attracted major attention, and there are two things to consider here. The architects wrote a very brief statement about their approach that was agreed with the Historic Royal Palaces, which I'm going to read you, because it's probably easier. And it says, 'Rather than adopting a moment-in-time approach to further repair and restoration, we have imposed a series of baseline principles that will ultimately see the screen returned as closely as possible to its original condition.' 

That's quite tricky in my view because what is its original condition and who knows what it was? And an example of that, I suppose, in the two images on your right-hand side of your screen, one shows the original mask and scroll work that was taken out, and the bottom image shows the replacement. And it's fairly easy to see, even though there's massive losses from the original, that there were elements of the replacement that do not match the original. And so we have a question that arises, and it will arise all the way through this talk, of what is original and what isn't and what is important to save, which I'm not sure what the answer is. And I think it is such a difficult subject, but I am raising it as an important issue about what we consider we are saving, and if you project this forward with ongoing restoration over years and years and years, we'll eventually end up with gates and screens made by a series of blacksmiths over many years in very different stages of quality and workmanship. And so we need to think hard about how we approach these things. 

And this just another image about the paint. There are two things here. One is that there was no evidence at all that these were ever gilded apart from a couple of documented verbal descriptions that says there might have been some gold. So the gilding on these is a wish, I think, from the Historic Royal Palaces at the time to make them spectacular and stand out. We do know, from paint samples, that the gates and railings and screens were originally this pale grey colour, which is absolutely correct – usual and frequently found colour on ironwork of this period. But you will see on the right-hand side that there is a slightly darker grey green that's been added, so we have here a whole combination of things – many, many forms of restoration, much of which is not original, but we have them back in a visually good and sound condition, so most people, you wouldn't know that they're not Tijou, and we have various stages of decoration, which are represented. So I know it's a work in progress, but it's quite interesting to see as an example of how these things progress through time. And I think that I'm going to pass over to Alex now, who seems to have disappeared. 

Alex [19:27] Forgive me. 

Sophie [19:28] I think we have lost Alex. 

Alex [19:29] No, no. 

Sophie [19:30] There, you're back. 

Alex [19:32] It's referring to condition assessment. Along with background research already covered by Rupert, condition surveying is critical to identifying not just the obvious issues but also the underlying causes that are driving them. And the production of a detailed report will inform any decision on the level and form of interventions that are scheduled. A solid understanding of techniques and materials is essential when addressing ironwork. Now, this may seem self-evident, but it is often not the case. For instance, there is an enduring confusion in specifications over correctly identifying cast and wrought iron. It's on a par with confusing bricks and concrete. They each have their strengths and vulnerabilities, and different approaches are needed when conserving them. When knowledge is lacking, a specialist should always be consulted. As well as what Rupert said earlier on, we will be addressing some of the visual differences to look for later on in the talk. The condition of the protective coating would generally be key to the condition of the ironwork underneath. Areas where this has failed always require closest examination, and bubbling beneath the surface should be explored to assess damage. And environmental factors are also important, such as encroaching vegetation subsidence or high wear through constant use. 

Now, when doing a condition assessment, access is not always straightforward. Allowance should be factored into any assessment. Here's an example of ideal access, at North Mymms Park. You can get all the way round it. You're not going to be bothered whilst you do so. And at the other end of the scale, there is the balcony and weathervane on the Caledonian Clock Tower. Now, occasionally assessment's made just a little bit harder by undocumented and overenthusiastic extraction, as happened with these earlier 18th-century listed railings, which are on the bottom left here. This obviously is best avoided. It adds considerable cost to the restoration and the historic record and is likely to be noticed by the planning officer at some point. 

Rupert [22:44] Sorry, I have microphone muted. Following on from Alex, this is just a list – and it's a minimal list – of really what needs to be included in any specification for the work to historic ironwork, and it's really split into perhaps two major things, which is the background research and brief, which is absolutely crucial, and it really goes back to Hampton Court and Tredegar and other things and Hartford Hall. And the other half is the technical section, which will cover all the performance: the level of work, the quality of work, the coatings, the cleaning and all the things that are practically involved in the restoration. And finally and definitely not least is the recording of all the work, and to some degree – and we'll include it in the specification and contract – is the issue of performance and how long a client should expect the work that anyone undertakes during restoration to last, and we will come on to that in terms of coating and other things later. 

But the real question is, who prepares the specification? And it obviously needs, if possible, to avoid a potential conflict of interest. If a blacksmith writes a technical specification for the work that they are tendering for, it should in ideal circumstances form part of a much larger document, which will make sure that is prepared and submitted in a format that can be clearly and fairly assessed, and Alex will tell me better and others may comment, but I think it's usual that blacksmiths – when it should be not the case – that blacksmiths do not write their own specification. Fine to write the technical specification, but the rest of it probably should be done by others. And I think that's probably all I've got to say about specifications for now. The list is there, but obviously it is not exhaustive, so I will now pass back to Alex. 

Alex [25:12] I think this is still you. 

Rupert [25:14] Oh, well I could-- Yes, it is me. I do beg your pardon. This is just one instance that we'll talk about. These are the railings and gates at the Royal Academy, Burlington House, and the issue here was that the specification was written, and the idea was that they would be restored in situ. Obviously, that causes massive problems in terms of cleaning them, and where they needed to be repaired – doing repairs in situ – the gates obviously can be removed. But the railings, in particular, couldn't be, but it was decided for practical reasons, although it would generally go against conservation principles, to cut them out. So all the railings, both within the courtyard and on the street, were cut out and removed. Now, that's an ethical question of whether or not that was right, and it might have been-- even if it was wrong or right in terms of conservation, it was definitely controlled by the client and issues of health and safety and ease of work. So there are factors way outside the technical restraints of working that govern conservation work. And that's the only point I want to make about that, is there are many ways to skin the cat. Alex. He disappeared again. 

Alex [27:06] Sorry. Following on from what Rupert's just said, it is ideal to conserve or restore items in situ to avoid the potential for damage to an item or its surroundings on extraction, or the potential damage and cost incurred in transit. But it should always be balanced against other considerations. As well as being a controlled environment, a good workshop will always have the right tools to hand. This widens the options available to the conservator, including hot works, which is often restricted on site. 

Practically speaking, it also avoids time and expense incurred getting unexpectedly needed items. There's always something and when the site is isolated, as is [Hearst Castle?], it's not always straightforward to pop out and grab what you need. There's generally increased labour costs with sustained site work – overheads like accommodation and subsistence. Some places are accessible by the public and this often leads to health and safety considerations from noise, dust, sparks or fumes. It can also cause restricted working or isolation of areas that are normally needed for access. There are great opportunities to demonstrate conservation in action, but sometimes time also needs to be factored in to answer sometimes a lot of questions from the curious.  

Of course, some things, like railings, if the fixings are sound, and sometimes they're just too huge, it's not always practical and sometimes it's overly invasive to remove them, so I mean all of these are factors which will affect it, affect the decision making. The great British weather, even when not near the sea, is unpredictable, and many processes are undermined by damp or cold conditions, most notably coatings, which will rapidly fail if applied in sub-optimal conditions. Of course, this can be minimised by building covered frameworks over items, some larger than others. But again, this involves increased cost, all of which should be factored in. 

Now, these rather splendid gates and railings from Lambton Castle needed too much work to make in situ repairs practical, for some of the above reasons, and they were taken out over the course of a day. Even though the piers are over five metres tall and the curved railings extend roughly 13 metres out on either side, it is in the nature of most gates and railings to stack without taking up too much space. It's obviously important to have a good relationship with a trusted transport company, who are sensitive to the particular requirements of heritage projects. As much as the transport, the cranes are a crucial element to the extraction and the reinstallation of larger items, particularly. The picture on the left, we've got one crane easing the pier over to one side to enable the other one to extract the throw and side gate, which had corrosion jacked into place. Obviously, planning and coordination are critical. 

Now, moving on to wrought iron. I should clarify that the historic wrought iron that we're talking about is a material. It is different from the modern steel used to make many often-mass-produced items, currently advertised as wrought iron. There's been no industrial production of either type of historic wrought iron since the '70s, and as such, it's a finite resource. Commercial production of [rolled?] stock from reclaimed puddled iron is available from one business in the UK. It is more expensive than mild stell though. Here are some pictures of salvage chain ready for rolling into section. Chain is ideal, being it consistently very high-quality iron. 

Now, Rupert covered the two different processes-- two different forms of wrought iron and their nature, their fibrous nature earlier on. And on the bottom left here, you can see on this nick-break test, the distinctive grain-- If I bring out-- Forgive me. OK, well, there's no arrow. It's the picture on the bottom left. The distinctive grain – ah, it's there now. Hoorah. Thank you – in the middle there. Both forms of wrought iron lend themselves very readily to the forging process, becoming softer at heat and more easily fire welded than non-steel. It should be said that mild steel, or pure iron, can be used to create all the traditional fixing styles and motifs commonly found in old ironwork, but you do have to work quite a bit harder to achieve it. 

And not all heritage work is wrought iron. You've got Charles Rennie Mackintosh's railings on the Glasgow School of Art, all of which is steel. As time passed, it became common to use cast iron, which works well under compression in culmination with wrought iron, each playing to their strengths, like these gates and piers from the West Dean Estate. And on the right, we've got a picture of a slightly rough fire weld from a very old set of Spanish gates from Seville. It's been heated to make it visible. Generally, they're not. If they can be found, it's only by the presence of a very fine seam in the surface metal and often not even that. But it's a very, very strong fixing when it's done well. 

If you look at this picture of the Clifton Gorge. It's from the laying of the foundation stone through Brunel's suspension bridge, and if you look carefully, in the upper part of the picture, you'll see a thin line that runs from the top of one side across to the other, with a little dot in the middle. This is made of a single wrought iron round bar, made of lengths fire-welded together on the Ashton Court side and pulled across, and it was used to support a basket – that dot in the middle – for transporting workers and materials. While modern health and safety would probably take a fairly dim view of this, it's still quite impressive and is an indication of quite how good the Victorians got. 

Now, the grain that's present in wrought iron will tend to cause it to split if not forged sufficiently hot enough. These splits can often be found where holes have been punched and drifted. This can be seen on the middle bottom and on the right-hand side there. Also, corrosion can sometimes find its way into floors in the laminations and lift the metal apart. You can see this on the left-hand side with this section here. This is called a roke. Both of these things are useful to look for when trying to identify a material. Cast and steel are homogenous. They won't do this. 

A few more identifying features are older wrought-iron section has an uneven surface from being forged into shape, rather than rolled, and this can sometimes be felt if you run your hand down swellings where material's been punched and the use of tannins, like this up here. It's a common feature of forged work but is equally true of forged steel, but if it was made before about 1900, it'll almost certainly be wrought. Foundry stamps are generally stamped into the metal, and you can't do this, obviously, with cast, and they tend to be raised if they're there at all in cast iron. A really useful thing, particularly relating to impact damage, is that wrought iron will generally bend if sufficient force is applied to it. Historic cast iron will snap. If it's bent, it's almost certainly not historic cast. Having said that, the reverse is not always the case. Occasionally wrought can [share?] cleanly, so that only works one way. A more invasive test, such as the nick-break that we've seen and spark tests do exist, but they're generally inappropriate when you're surveying historic material. 

Rupert [37:43] Yes, thank you. I just thought I'd very quickly show you four examples of cast iron. On the top right is the Eagle Slayer. It's the very first cast-iron sculpture ever made by Coalbrookdale, and it was exhibited at the Great Exhibition in 1851. To its right is the Cornhill Pump, which was cast in 1799. These are both prior to their restoration, and there's probably someone listening who was involved in the Cornhill Pump, definitely. And the bottom left is the Bandstand in Clapham Common, which dates from 1890, and it's the largest bandstand in London. The only technical interesting thing about this is the hollow cast-iron columns actually double up as the rainwater downpipes, which is quite a cunning use of the cast-iron structure without having to have any ancillary drainage. 

And on the right-hand side is one of my favourite objects in the country, which is the Whiteford Bay Lighthouse. It's cast-iron plates. It's a grade 2 star listed construction, and the plates are held together with cast-iron bolts, and each of the bolts weigh nearly two kilos, and the only reason that this is still standing is because they used cast-iron bolts and not wrought-iron bolts, because had they used wrought-iron bolts, they would have corroded and by this stage it would have fallen down long ago. And very quickly, I wanted just to make a case of how things change. On the left-hand side is the marble Queen Ann monument outside St Paul's Cathedral, with cast-iron railings, which are late 19th century, and on the right is a picture of the monument taken probably somewhere around 1875, which shows the very, very important sculpture by Francis Bird, which was taken away and now is languishing as a monument at risk in a garden near Hastings, or in a field near Hastings, and they at the same time of remaking the sculpture as a so-called copy, they decided to take out the absolutely wonderful wrought-iron railings that surround it, and it just shows you how change happens massively and perhaps in this case unnecessarily. But it's the nature of fashion. 

More cast iron. These are railings at Wimpole Hall surrounding the church, and they are a combination of cast-iron uprights and baluster panels with wrought-iron top-bottom rails and little intermediate round bars. And the image on the right just shows what happens with the two pieces of material together, that the corrosion caused by the wrought iron has pushed out and split the [pored?] lead plug that was holding the two pieces together. And that is, where we were talking about earlier on, the difference in material. If you put the two together, you get corrosion problems, potentially, if not maintained, which we will come onto later. 

Just two very quick slides here of one of my pet problems in terms of conservation, is the loss of historic park gates and railings. Often, they're not careful. They are often made in unique form, and they generally are so important to the landscape. And what happens if they are not maintained, they get affected by corrosion, undergrowth, bad care and generally dereliction, and the loss of some historic landscape is very, very sad. The centred one is really quite interesting. These posts, or in fact, pressed steel, they're in Ireland and rather wonderful, but it's the only example of these I've found in the country so far. And as such, I consider them to be highly significant and important but often neglected. 

And just some other examples of cast and wrought iron, in most cases gates, and obviously you've got the issue of treeing growth and other things that happen to things like this, which is all part of the nature of the rural environment in which they're sighted, and there is nothing worse than to come up to a property where they've taken out historic railings and replaced them with modern uniform, generally badly made and badly designed railings instead. And in my view, they are equally as important to the historic landscape as England as the more significant and major wrought-iron work that we are mainly concentrating on today. And I think I'm back to you, Alex. 

Alex [43:57] Indeed. We're having a look at some common problems. Iron, unlike many other commonly used metals, the oxide layer does not stabilise on the surface and the reaction is ongoing, particularly aggressive in marine environments, where the chlorides drive accelerated corrosion. The picture on the top right was once a galvanised tube. As well as the loss of material, rust has seven to ten times greater volume than iron. Its production in a confined space caused corrosion jacking or rust heave, deforms frames, cracks cast iron and stone. 

Common problems are generally due to a lack of consistent maintenance outside of accidents or wear on unlubricated moving parts. It's corrosion that's driving the degradation of iron gates and railings. And the presence of water drives this process, and the coatings are designed to insulate the metal from it, while most exterior or ironwork that's situated in sunny, well-ventilated areas will corrode slowly. The exception is wherever water can get trapped. Now this pattern means we see the same set of problems repeated with small variations again and again all driven by lack of consistent maintenance. There are some common design elements that lend themselves to creating the ideal conditions for corrosion, such as mating faces, crevices or water traps, where coating failure results in water ingress, and they are by their nature hard to maintain and will retain moisture. 

Now, on the bottom right-hand side, we've got corrosion heave here and here on both of the shadow rails. It's a very typical pattern of damage. Also affects slam bars. They're very hard to access once problems have started, and this cast-iron detail in the middle has also been snapped off - again, probably rust heave. And there's classic damage to the water leaves. It's a design classic – leaves that hold water and are, by their design, very hard to coat effectively. Now, on the left, we see some fairly heroic corrosion jacking. Now, I raised this as an interesting thing, because if you look at the same place on the post-conserved, post-restored top rail there, what's noticeable is how little of the material is actually gone. Given the opportunity, that rust jacking would probably have gone quite a bit further. 

And we've got a typical corrosion profile on the top left up here, with this repoussé leaf. They're often the first things to suffer following a coating failure because they're made of very thin material. They don't have much material to lose, and they're hard to coat effectively, starting with the mating faces on the material that they're laid on top of. And it is a typical corrosion profile where it's lying against the supported stock, and if it was allowed to continue, the leaf would be heaved off and possibly lost. Collars tend to blow. They often have tapered section, which feeds water into them. And this detail here in the middle could not have been better designed to collect and hold water. This obviously reduces the life of a coating and encourages corrosion when it fails. In this case, it's a confined area. Another very common driver of corrosion is a build-up of vegetation or detritus at ground level. This is a critical part of maintenance to avoid this happening. It maintains a high moisture level, and whilst the rest of this structure is largely intact, the feet have almost completely rotted off. Ironically, the lead fixings were in perfect shape. 

Now-- Hang on. Forgive me. On the left-hand side here, is the other side of the problem with rust heave, where it comes into contact with stone. If the iron is embedded in stone, the corrosion jacking will fracture it or crack it and, as has happened here, will occasionally just split whole chunks off. This can and often does develop into structural issues because it's generally the fixings that's holding everything in place. Now, here's an example of a sadly not entirely uncommon problem. On the right-hand side, you can see the result of a vehicle impact on the really impressive gates to Mentmore Towers – fairly straightforward cause and effect but attached to the stay that will need to come off to be straightened and restored. This is a slightly Heath Robinson bracket here, which stabilises the throw. Presumably, this was considered enough of an issue for it to be needed. And we have a problem if you're going to take the stay off. You're going to undermine that, and so a cursory further inspection revealed that the throw that would need to be stabilised to do this work is attached to the rail below it by a series of 15 cable ties. 

Now, this rail attached by cable ties is all that's holding the gates up. The top pin here on the right-hand picture goes into that rail at that point. On the left-hand side, the bigger picture on the bottom left where the arrow is, that rail has almost completely come out of the pier. To put this in perspective, the gates are close to half a ton each. I don't think the cable ties would hold it if they decided to fall. If it did fall, it would sustain damage, probably the throw as well, and it would result in distinctly suboptimal outcomes for anything that was underneath them as well. It's just a good illustration of the need to take into account previous repairs and how they made be affecting an item's structural integrity. Also underlines the need for a thorough understanding of construction and stress loading when assessing damage. 

And-- 

Rupert [52:27] Oop, right, me. Going on the cast iron-- I'm very conscious of time. I'm hoping that those who are listening are able to stay longer, but I'm sorry; we are definitely going to overrun today. But we'll whizz through this as quickly as we can. The centre picture and the top right are railings from Buscot Coalbrookdale castings, and the reason I'm showing this is that the only reason that the cast pier is cracked is because the wrought iron screws that are holding the panels together have corroded, which has caused this cracking of the cast iron. On the right-hand side is some in situ welding of cast iron, which is possible, but generally is not very neat, and as you can see in this image, it's rather lumpy and everything else. But it can be done in an emergency and a way to keep things stable and structurally OK. And on the bottom right is the classic combination of wrought iron and cast iron, where the wrought iron is split and lifted the capping off the baluster. 

And another example of this is the Warrington Gates, now called the Golden Gates, although these [indistinct] Coalbrookdale again, dated 1862, grade 2 star listed objects. Were never gilded until 1977, where the queen's jubilee, the council, decided it would be very nice to smarten them up. So they've now been fully restored, with the gilding, and the paint colours are not as original, so what we're looking at again, going back to Hampton Court and Wimpole and other examples, visually we are not looking at something that existed when these were first made. The reason I'm showing this is for two reasons, for that one particularly, but secondly for the missing detail here and here, where the only cause again, rather like the Buscot example, the reason that these castings have fallen off is that the screws that were holding them in place, the screws and pins, had corroded and so a lot of the cast detail attachments have failed, so they needed to be done, and there is a little bit of rust jacking you can see on the left-hand image where my arrow is now. But they have now been fully restored in their new former glory – well, 1977 former glory. 

We're now just going to move on very quickly to cleaning. Obviously cleaning, depending on where you're doing it, is particularly difficult sometimes. If you have to do it in situ, the control of the environment is very important. And I've listed in the centre the various forms of cleaning that can be adopted, and these two images show dry ice blasting on the right-hand side, which are the test trial we did at Osterley Park, because we're very close to a grade 1 listed building, which is occupied by highly important furniture and paintings, and of course, dust is one of the critical things that we'll have to prevent getting into the house, so we tried dry ice blasting, which was successful, very noisy and expensive. And on the right-hand side, this is ultra-high-pressure water cleaning, using water at about 32,000 PSI, which is fine on solid objects. This demonstration was actually working on some zinc sculpture, but it's certainly applicable to ironwork as long as you don't have delicate items, which obviously the pressure of that would damage them significantly. But these six methods of cleaning are ones that we would consider, the pros and cons of which we might try and cover if we can later. And now back to Alex. 

Alex [56:50] I put these up purely to illustrate some of the earlier points. Blasting is sometimes quite aggressive and will damage very, very fine sheet work, rather like this ram's head, although some of the alternatives like flame cleaning, apart from the slightly restrictive PPE and clean-up due to the lead, but that is equally true of blasting where lead paints are involved. You have to be extremely cautious with this panel on the left here from the Miserden Estate. It's from a gate from about 1705. And flame cleaning's very effective, but here, these skirts that lie underneath this front piece, they're zinc. These stirrup leathers up here are made of very, very thin brass, which is also the inside of the petals of this flower, and these are lead. Obviously, these have much lower melting points, and if you put a flame on them, they won't last very long. Sometimes dipping is restricted by the size of items. And also it has a tendency to leach into small cracks and can be quite hard to remove, and so whilst there are pros to every one of the different processes, there are equally cons and they need to be weighed up quite carefully. 

Now, we're on wrought iron repair, and again, I'm conscious of time, so I'm going to do my best to speed things up. You've got a car-- I think one of the most important things that I can say is that there is one practical factor that will lead to suboptimal outcomes: when restoring historic ironwork of really crucial influence will be in the craft skills of those contracted to do the work. Metalworking has moved on, and many modern metalworkers don't have the training in traditional techniques. If the contractor's ability and understanding fall short of that of the original craftsman, the results can be disappointing. And this was-- the item of the right is supposed to be a copy of the one on the left in this picture, and it was part of the Long Water at Hampton Court Palace for some years before it was removed. It is a slightly extreme example but, I think, makes a point. 

On the left, we've got some repoussé repairs brazed in sections where the material was lost – these three areas here – and a replacement leaf. The two sections above were the only survivors of 16 leaves. One of them was found in the ground, which was a great relief because it meant we had at least got one example to copy. 

Now, whilst a lot of the time, original techniques and materials, or techniques, are ideal, they are sometimes limited. A good restorer will have a wide range of treatment options and a good understanding of their strengths and weaknesses while retaining as much historic material as possible. For instance, the fire weld, whilst traditional and in many cases ideal, is often invasive in that it requires dismantling an object with a loss of the original fixings, along with a historical record that they contain. And whilst not historically accurate in most cases, welded or brazed repairs when done with care can often a smooth and unbroken appearance when introducing new material. Their advantage is that this can often be achieved while the elements are still attached, with the retention of the original fixings and context. These severely jacked panels here, with blown collars, have been bent back into shape and the badly wasted areas replaced with new wrought iron stamped at each end of the introduced material and the original collars replaced to avoid getting water back into the crevices. Particularly where there's material loss. It's important to seal the areas with some flexible filler. Hard filler will often crack, which opens a whole new can of worms. Whatever technique is used, it's important wherever possible to date and mark introduced material. This adds to the historical record rather than obscuring it. Detailed recording at all stages with a reason behind every intervention is equally important, but it has to be said more easily lost than stamps on the metal. 

Now, I can't go through this without talking about removing lead, because it's such a common problem where the stone has jacked or the bases of things have rotted away. It can be done by drilling out. It's slow, but it avoids excessive damage to the surrounding stonework. If the stone is of lesser importance, the iron can be cut and the fixing with the lead, core drilled out, to be reattached before reinstallation, or the stone can be replaced entirely. Again, case-by-case basis. A well-tamped and chamfered lead fixing will last for potentially hundreds of years. If there is any dip at the base of the fixing, water will pool there. It's going to be interesting to see how the resin fixings, now commonly used, will be holding up after timescales like that. Over to you, Rupert. 

Rupert [01:04:10] I'm going to very quickly go through cast-iron repair. This is just an image of metal stitching carried out in the cases of the two images on the left-hand side on sections of the construction of Albert Memorial, and this is a cold process. They are described by the image on the right - very strong and very suitable where you cannot undertake any type of other repair and you definitely want to consider recasting. 

Other forms of cast-iron repair which can be done. The image on the left-hand side is just of the Eagle Slayer, and this is a Coalbrookdale. You can see here, there's a line with [indistinct]. And on the right-hand side is a cast-iron gate from St Leonard's Church, whereas a temporary repair they put clamps in. Now, clamps are absolutely fine as a temporary repair, but the problem is, of course, that they generally are made out of steel and they again will corrode if not looked after and cause the same problem all over again. But as a temporary repair, that is one way round it, but as I stress it should be only temporary. Here is an image of gas fusion welding. This is a way which you can only do off site and for relatively small components. You build a kiln around it. You heat the whole iron component up to red heat and then you apply with an oxy acetylene torch cast-iron welding rods. Very, very strong repair, expensive to do, but it saves the original object, so it is another option. 

And we're now onto paint – very quickly. This is the Cenotaph, which is a steel ship's mast, 90 feet high in the centre of Sheffield. The image on the right-hand side is the degraded paint. One of the problems here was lead-based paints and the underlying coatings, and it was decided here that it was easier to encapsulate the paint and treat the rust and the topped coatings, which were not lead based, were rubbed down and the whole thing was repainted, keeping the lead paint in place where it was still sound, because the health and safety complications of removing it are too extreme. 

Clearly, the middle picture at the top is of paint samples, showing the entire history of coatings – absolutely crucial – but the point I would make that paints should be taken before work starts, and certainly if dismantling is undertaken, to look very carefully again to make sure that there isn't other paint samples that exist which haven't been cleaned off by past restoration. And in the bottom centre: paint thickness gauge, and it's a bug-bearer of mine that many, many specifications for paint are provided but the paint is not applied in adequate thicknesses to the specification, and it's one of the problems with spray coatings in particular that not adequate protection is provided, and there are many examples that I've encountered over the years where paint has started to fail completely unnecessarily because the paint has not been applied either correctly, and painting is an art in its own right, or to the right specification. And I'm not insisting with specifications that we test the paint that is applied to newly restored projects to make sure that the specification is adequate and there isn't going to be a contentious, possibly legal problem at the end of it. 

Alex and I can share this really, but this is at [Clandon?] Gates, very beautifully restored in situ, and the list on the right-hand side is just the types of coatings that we would consider. I won't go into what electrophoretic coatings are, but obviously there are rust converters, which can be good, bad or indifferent. Thermal spray coatings, and or galvanising, is generally considered for important historic ironwork not to be suitable because it's irreversible, and the issues of reversibility in conservation generally is always a problem. But as it stands at the moment, it is generally not advised to use thermal spray coatings on historic ironwork. And then you have a whole list of paints. One came [indistinct] midcoats, and Alex has covered, to some degree, epoxies and polyurethanes. There is a favouring to oil alkyd paints. And then of course you have the very, very traditional standard oil-based paints with lead, which is in my view not to be used, even though you can get authority on grade 1 listed gates to use them, but they're a health and safety issue and continue to be a problem for those that are going to follow on. And this is Alex. Alex? 

Alice [01:09:54] Hi Alex or Sophie, shall we do some poll? 

Alex [01:09:59] Yeah, go for the pole. It's time. 

Alice [01:10:27] It looks like we're at the end for the poll, Alex. 

Alex [01:10:32] Well, it was a horrid trick question. The supporting upright is wrought iron and the bar going through it is some more galvanised steel tube – well, was, I should say, once in its past. If it's a smaller job or a less important job, that little paint sample down there is an example if the budgetary restraints mean that paint analysis can't be done by a professional. If you just want to know about the colour, before it's removed – if it's going to be removed – chip some of the old paint off and just have a visual look. It will give you an idea of what the original colour was. And as a rule of thumb, it's always good to be guided by that for historic accuracy. The [Mims?] Gates are up there for a couple of reasons, but I'll only talk about one of them, which is whilst there is no encroaching vegetation, it is surrounded by trees, and one of the things that can happen is sap and general detritus can fall on it, so it's quite important to up the maintenance schedule in those occasions. Over to Rupert. 

Rupert [01:12:07] And this is purely an example of very well-restored and painted ironwork, and I'm only showing it because, as an example, that this is the Palace of Westminster, and it's the reintroduction of historic paint colouring and gilding as it was and the use of semi-matte paints to simulate the older style of paints. We generally would consider the use of gloss paint on historic ironwork to be not acceptable or correct, and it just looks visually awful. And we're here again with Alex for other issues related to paint. 

Alex [01:12:54] It's just relating to the degradation of paint. The example on the left is from Ranger's House. I understand it's only two years – it's an old picture – but when this picture was taken, it's two years after they were originally coated, and there are some signs here that there is incompatibility issues, and the water leaves are doing their thing. It's being allowed in due to a failure of the coating. 

The two pictures on the right-hand side. The picture on the bottom, if you look carefully, there is water on there. That coating is seven years old, and the top picture is exactly the same coating recoated over the top. And you notice the way that the water is beading up. Both of them are wet, and it just shows you the hydrophobic qualities of a fresh layer of an oil-based alkyd paint and the hydrophobic qualities and indicates that seven to ten years is a good time. I think Rupert's about to do maintenance, but it underlines the need to regularly recoat coatings, preferably before they fail. You'll save a great deal of money. 

Rupert [01:14:35] We're going to go very quick on this. This image shows everything that's wrong with paint really. We've got algal growth, paint failing because of ink compatibility would be the underlying paint, we have corrosion and we clearly have a long-term lack of maintenance. And if one was going to stress anything about these particular projects relate to maintenance, forget the grandstanding projects; maintain regularly. And when I mean regularly, inspect every year. If it needs retouching, you find corrosion, then repair it there and then. If you do that, you will get round the problem of this endless amount of huge expense on major restoration projects, and it's a common problem, and even my best and most informed clients will fail to do this, unfortunately. It's something that has to be done if you want to save money. And if you were to take the [Rawington?] Gates as an example, had they been looked after properly in the years since 1977, it wouldn't have required the 400 thousand, or 350–400 thousand pounds, that it cost to restore them. And it's just sad, in my view, and it needs to be addressed. 

An example which I just want to point out: these are the church railings that I showed you, Davies brother railings of Chirk castle on the left-hand side, and we're just writing a new spec for this, and I asked the property manager what paint was used last time, and no one knows. And they're pointing out the issue of record-keeping and making sure that it is recorded properly because it solves so much later problems of incompatibility. If you don't know what paint was used, how are you going to put a new coating over the top that you can be assured, without doing endless trials, which you cannot do quickly. 

And on the right-hand side are gilded gates from [Clifton?], and I can't show you an example of close-up, but they have started to rust already, and that's because of insufficient paint coating. So the paint maintenance and proper painting are probably the most-- if you want to take anything away from today's talk, that would be it: care and regular care would be my strong advice, and if anyone's still with us and wishes to ask this gentleman a question, then please do. And I do apologise greatly for the overrun, but I hope we managed to skip through it with some – apart from my phone going off – with some degree of informative information for you to go away with. Thanks very much. 

Alice Hi, Rupert. Hi.