Conserving War Memorials Webinar Part 2

Speakers: Clara Willett, David Odges, Rupert Harris, Matt

Clara: Welcome to part two of our war memorials webinars. In this second part, we're going to look more closely at the materials which are commonly used, that being stone and metal. Understanding these materials is key to caring for war memorials. So in this webinar we're going to discuss the conservation approach to cleaning, repairing and maintaining these materials in the context of these significant heritage assets. And as Matt mentioned, if you haven't already, I really encourage you to watch part one where we talk about the significance and the challenges of conserving war memorials. So I just want to start by briefly introducing myself.

I'm Clara Willett. I am a Senior Historic Building Advisor at Historic England. Before joining Historic England, which was then English Heritage, in 2003, I worked as a stone conservator in private practice and in my role at Historic England, now I currently focus primarily on masonry conservation, including war memorials, terracotta and the Strategic Stone Study. And I'm delighted that we have two experts, David Odgers, and Rupert Harris. David, would you like to introduce yourself first, and then, Rupert?

David: Yes, hello everybody. I'm David Odges. I trained many years ago at Wells Cathedral and ran Nimbus Conservation until 2005. Since then I've run my own conservation consultancy business. I am an accredited conservator and spend my time teaching writing and advising on stonework.

Rupert: And hello everyone, I'm Rupert Harris. I trained initially at the V&A and in metals conservation and from 1982 I've run my own practice and I now advise not only Historic England, but also the National Trust and Royal Collection and many others, apart from running a practical conservation business.

[They discuss a technical issue with the webinar recording]

Clara:  Just before we make a proper start for those of you who are new to Technical Tuesday, I’d just like to let you know a bit about the Technical Conservation team. We're a group of specialists including conservators, scientists and engineers, and we undertake research and provide advice and guidance on technical conservation issues.

And the first link that Matt is posting in the chat room for you will take you to the main technical advice page on our website where you can find all our technical advice and all our research reports, and PDF guidance documents are free to download from our website, and I think the second link you're going to put in it, Matt, will take you to the catalogue.

So there is a downloadable catalogue that you can look at all our advice and guidance and there's also obviously, as we will keep mentioning throughout this webinar, a whole wealth of more information that you can read about to do with war memorials. And if you don't know about the Technical Conservation Newsletter which is emailed out on the first Tuesday of each month, this will let you know about new technical conservation guidance, and publications or any forthcoming technical conservation training events. So if you'd like to add your name to that and you haven't already done so, then you could click ‘Yes’, I think Matt you're going to put that up on the chat room there.

Matt: I think there's a newsletter coming out tomorrow actually, if we can get your names onto that list, you'll receive a newsletter tomorrow.

Clara: And if you do click yes, again, don't worry, you won't receive the email twice. We've got a list and you'll be added to that list, so that's fantastic.

Matt: So still a few more, just one or two coming in there. There you go, all done.

Clara: Lovely, brilliant, thank you. So just to give you an overview of the webinar, so you could see where we're going. We've got six sections, but the sixth section is a question and answer. So as Matt said, if you want to put any questions in the chatroom, hopefully we'll have time at the end to answer those. But you can see we've got five sections to go through with you. So each of us will be taking those, so I'll hand over now to David and we'll start with assessment and survey.

David: Yes, thank you, Clara. So it's good to start by reminding ourselves just what a magnificent and diverse collection of war memorials we have with very significant commemorative and aesthetic values so that even A. A. Gill who's perhaps better known for his trenchant and acerbic criticism of anything from food to art, waxes lyrical about war memorials. We have a lot to cover today, but everything must start with a thorough assessment and survey. This slide shows the main factors that need to be considered in order to build up a full picture of the condition of a war memorial. The small icons indicate how best to achieve this, so for material identification we've got visual assessment, maybe microscopic assessment and maybe archive records for structural condition, visual and measurement material condition is really something for observation, environment and orientation are self-explanatory. Establishing the main causes of decay again is a visual assessment, but also one that requires us to use our brains to understand what we're actually looking at. And previous interventions again, are visual things, but also you may find good records. So the prevalence of the eye icon reinforces the idea that observation is the most important element of any survey in assessment. But these are only part of the story for us, discussed in detail in part one of the webinar. It's the heritage values and significance that can play a dominant role in deciding treatment. Rupert, is there anything specific in the element of assessment that's pertinent metals that isn't included in that list? I think from the metals point of view, the things that we would be really concentrating on the severity or not of the surface condition of the metals and structural problems, which are generally caused by failure of armatures or fractures, usually caused by poor casting techniques over periods of time which get worse partly due to corrosion, or possibly due to vandalism, but otherwise the points that you've already raised very much cover metals as well as they do stone. Excellent. Thanks, Rupert, so we've now gone through assessment, but it is a very important element of the whole process. But, of course, the most important thing is to know or find out the materials that have been used in any war memorial. And obviously, war memorials predominantly have a large stone content, but as illustrated in this slide, there's a huge variety of stone types, and identification can be difficult, but the clues can be found by close examination of the stone itself, knowledge of local quarries, and I'm hoping that Matt will put up here a link to the Strategic Stone Study which is a very useful resource for finding out local quarries. But also you can look at soiling patterns, which very much tend to give you hints as to what the stone is, and of course local history. Local archives will provide information as well. Depending on where you are in the country, of course, there will be different types of stone, but many of the larger monuments use Portland stone just because of its ready availability, and this was also the stone of choice for the Commonwealth War Graves Commission. Rupert, you're going to….

Rupert: Yes, as far as metals go, obviously we're dealing with two types of metal, nonferrous in the majority. These are all copper based or copper alloys, so obviously we have bronze which would definitely form the majority of the memorials that we have. But, as you see on the right hand side of your screen, there are a large number of brass memorials. Mainly these are found in interiors and we have to remember also that there are many thousands of war memorials, interior situations that need caring as well. We are predominantly covering exterior memorials in this in this webinar in the bottom right corner where it says a Copper (electroform). This is an exception which is quite often misidentified. Copper electroforms, for those of you are not aware, are formed from moulds where copper is deposited into a mould using the electroplating process. And, quite obviously, these are quite difficult because you colour them the same. They look the same as cast bronze, but are definitely not, and one of the factors which we will see a little bit of a slide later on is that the copper lecture forms are very brittle because of the way they are deposited. And they can suffer damage quite easily from impact. But in terms of their corrosion ability to auto ability with standard corrosion, they are very much treated in the same way as bronzes. And obviously the others.

Clara: I was just going to ask Rupert, what's the best way of identifying different materials are different metals?

Rupert: Very difficult when you're talking about copper alloys because most of them obviously have either corrosion products or patination on the surface, so they all, to all intents and purposes, look the same. But because electroforms, in particular, are very thin, if you were to tap them, they often sound very, very different than the cast bronze. They have a tinny, ringing sound. And that that is the way that I go around and find out. Occasionally you find manufacturers names. Elkingtons were affirmed as very specialist in making copper electroforms. And quite often, they are signed Elkington. So that would be a good indication, but other than that, it really is a visual inspection with the with the tapping. But it takes a little time. You need to go and find someone and understand the difference between the ringing sound that you get on the different types of bronze compared with electroforms.

Clara: Thanks, great.

Rupert: And obviously the other areas that we've got to deal with, are the ferrous metals, and obviously, in this area we're talking about, in the majority, cast irons and steels.

In the top left hand corner there is a cast iron crucifix, which you hopefully can see is heavily corroded, and obviously the sign of degradation of ferrous metals is rust, but with nearly all ferrous metals they will be painted, and cast iron we will have the situation occasionally where bronzes have been painted, and cast iron will have been painted, and obviously you need to know the difference and if you are sensible you buy a £2.50 children's magnet and keep it in your pocket or your bag, which is a very good way of sorting out one material, copper alloys, from the steels, but obviously the cast irons and wrought irons and steels are very usually the object themselves helps to identify what they're made of, but you've also got some issues where the two, the tank and the submarine gun, for instance, have other materials attached to them as well. They're not just made of one material, so that we have composite or mixed media memorials as well. And they obviously take quite a lot of study to make sure that not only is the metal in good shape, but other things like fabric or leather or plastics in the case of the tank are also in protected and in good condition.

In the bottom right hand corner there is an iron railing. Well, in fact the two slides, bottom centre and bottom right. These are railings that are constructed from iron, but they're covered in very thin copper sheet to look like bronze. And the right hand shows the splitting of the copper coating caused by corrosion of the iron underneath, and this can be quite a problem. We've got basically bimetallic corrosion, but obviously with irons, particularly the corrosion volume of the corrosion can be ten times that of the metal itself. So there's a huge amount of pressure can be applied to other materials by corrosion, and in fact,. I'm sure David will cover this, but the issue of rust jacking in stone from iron fixings is a significant problem.

Clara: I was just going to mention, Rupert, as well the importance of painted surfaces. It's often found on Ferris sculptures and other types of that metal work and the importance of understanding what painted surfaces you've got there as well.

Rupert: That's an extremely good point. We would undoubtedly, if we found memorials that seemed to be originally painted rather than being painted inappropriately later, we would undertake paint sampling and analysis and doing very detailed cross-sectional analysis, to make sure that, if repainting was to take place, then it could be done with the knowledge of history and science and in the right colour.

Clara: Yes, exactly, and we're now going to move on to common issues and defects, so I'm going to hand over to David now to talk a bit more about stone.

David: And we've gone one too far, and that's better. OK, yes, thanks, Cara. So for stonework the most obvious and frequent issue is really to do with soiling on war memorials because of course they have a very strong visual characteristic. And the soiling occurs in in many different ways depending on the substrate, the location, the previous interventions and all those other criteria we discussed earlier. So on this slide you just see some examples. On the left hand side, there we've got some differential staining from uneven runoff, which is often a result of the design of the memorial. So some places suffer wetting drying and some do not.

Top centre we've got to sulphation from pollutants which react with the surface to form black crusts.

Bottom centre is sandstone with mineralogical changes which cause darkening of the stone as a result of wetting, drying and migration of minerals. And then on the right, a very common fault from where you've got a combination of bronze and stone which is staining from the metal work. The copper staining is due to runoff. Apart from that type of soil in there, the main problems that occur with war memorials relate to biological growth such as bacteria, fungi, algae and lichens which cannot only be aesthetically disfiguring, but it can also cause dire deterioration.

The three examples. Just very simple examples here. Basically you’ve got a simple obelisk with lichens on the left. You got a graveyard cross there with algae on the on the stone. And then you’ve got moss collecting on the right hand side which is just to show you the variety of biomaterials that we get. Apart from the sort of visual characteristics that there is also deterioration which can be due to a physical effect in which the hyphae penetrate the pores of the stone and place them under pressure, and biofilms can produce bacteria which can penetrate the stone matrix and enhance physical weathering as a result of changing the moisture transfer characteristics of the surface and that can increase the potential for salt decay. There's also a chemical effect in which certain microorganisms secrete organic acids and enzymes, and these can alter the surface and cause minerals to be mobilised from the stone matrix.

It is, of course, important to remember that there are some rare lichens that are protected by law, so it's just worth bearing in mind that they're not an enormous number, but there are some and you would need to get a lichenologist to come along to tell you which ones they might be. But there's also decay to stonework as a result of salt attack, freeze thaw, poor stone and other standard decay mechanisms that are not necessarily specific to war memorials.

Of course, the slight decay of a stone surface on a war memorial can have a dramatic effect on the legibility of lettering. So even small amounts of weathering, which in a building might be considered acceptable, can take on a much greater significance on a war memorial. These images show a number of the sort of issues that we come across. On the left, there you have the, the Bamber War Memorial in Northumberland, which is very close to the coast. So it's export exposed to salt and wind, and the niche in which the cross is set doesn't really offer any protection. In fact, it may even be exacerbating the wetting and drying cycles. So as a result, there's a serious salt attack on the inscription.

On the centre, we’ve got typical sort of surface decay of marble and sugaring of marble due mainly to a combination of sulphates and heating and cooling cycles, so that the areas with higher surface area and lower volume are most at risk because of expansion and contraction.

Top right is very typical freeze thaw, where saturated stone decays due to expansion of the water in it as it freezes. And finally in the bottom right, an example of what basically is just poor stone and this one is probably due to expansion of contraction of clays within the stone.

As has been mentioned a couple of times already, of course the decay of lettering is a is a very specific element of war memorials. And depending on the type of lettering, this can occur due to a loss of support for applied lettering as in lead, for instance erosion of the inscription as we saw in the previous slide, or indeed erosion of the material used to fill the inscription. Understanding the mode of inscription, the type of decay it has suffered, is a very fundamental issue for war memorials. Rupert, have you got anything you wanted to add to that in terms of metal inscriptions?

Rupert: Not a lot, and only that's one of the biggest problems and causing the loss of both lead lettering and bronze lettering, is, as you said, the erosion of the stone around and behind the letters themselves. And if, as one frequently finds, when a letter falls off, you find that the letter itself is mounted upon a little piece of raised stone in the form of the letter or the number. And this problem makes replacement and reattaching of letters particularly difficult because you're trying to set a letter back onto a little raised amount of stone, and this can cause big problems and it is very difficult to do it neatly. The image on the top right hand side was very, very fine bronze lettering which actually just corroded. And nearly both lead lettering and bronze lettering quite often are applied with minute pins going into the stone. And once they've failed or corrosion is affected, or the strength of letter itself, they just fall off. Or in the case of that right hand slide. Basically it's just deteriorating, mineralised and disappeared. But the reattachment is particularly difficult. But I know we're going to cover that later on, so I think as far as that's concerned that's all I have to say about that.

David: Over to you again now, Rupert.

Rupert: It’s me again. Yes, I think the importance as far as I'm concerned, this is almost the most critical thing we're talking, in the majority in this session, about external monuments and in the majority cop copper alloy in this case, bronze is and it's very, very important to understand what the corrosion is and how it forms, and whether it is good, bad, or indifferent in terms of the monument.

Part of which is to do with the formation of what we call natural, but we have to understand that all these memorials were when they were finished in, the foundries were chemically paginated, which I will cover later, to usually a classic statuary brown bronze colour, and in most cases protected with a wax. Once that disappears, then the natural corrosion process takes over, and if you look at the figure on the left hand side, which is now almost completely green. And the in the majority natural patinas are formed from copper carbonates and copper sulphates and they are when we call them stable patinas. This is a good example. And the interesting thing about these green patinas are that, once they've formed, the actual corrosion rate drops dramatically almost acting and its own paint and a green patina of this type would take probably 130 years to form and there is a loss of material from the surface of between two to five microns a year, so over one hundred years we're talking about half a millimetre. So you can see that the actual corrosion rate in terms of damage to the bronze is very, very slow.

But obviously with war memorials, one of the things we concern ourselves over with is with the aesthetic, the look. And quite often, greens are not considered to be appropriate for memorials, and so we then have to consider what we do about dealing with the greens and we will cover that later.

On the right hand side there is an image of what we call active corrosion, or in this case pitting corrosion. And it's identified, particularly because of these bright green spots, and I want to just deal with the issue of bronze disease, which often when people see this, they refer to it as being bronze disease. Bronze disease, generally speaking occurs from archaeological and or marine archaeological sites. It is not found on monuments. This is active corrosion pitting corrosion, but it is not technically bronze disease. So if anyone sees a report saying bronze disease, I would very much doubt that that's the case. However, this bright green corrosion is very active and very aggressive, and where it forms, it will eat pits into the surface. So clearly when we're talking about maintaining and restoring monuments, areas where this type of corrosion exists are something that we would want to deal with very specifically, and to remove what is usually chloride in materials from the surface. And the way we do that, we will also cover later.

Other issues that we need to cover are where on the left hand side we have a painted bronze, which has then been graffitied. The paint frequently used is mainly a cheap quick way of restoring the look of the bronze when it's gone green or looks unsightly and there are many examples of, in this case, black paint, but use which is being applied to memorials as a quick fix treatment.

The other thing that we suffer is the loss of structural ability from iron fixings, in this case, across. And on the right hand side, obviously in this case, theft, and this is an electroform plaque and you can probably see on the left hand the right hand corner that it has broken away. And obviously as I said to you, these parts are very brittle and very, very easily stolen. So they are things that we have to cover and be aware of when we're treating bronzes.

And in terms of inspection, going back to the visual inspection that David was mentioning, and then the outset. Castings, if you look at the left hand side, there are two typical things you will find on bronzes, and they are a result of two things. One is porosity, and if you look at that slide, there are areas a little bubbly indents all over the surface. And this is gas trapped in the cast bronze at the time of making, and obviously with little pinhole size things like this, they can be the source of trapping pollutants and the source of obviously active corrosion in the case of pitting corrosion. And the other thing you will often find are these bronze patches which were put in by the foundry to deal with larger faults in the surface, which they put in to hide them. So we have a slightly different material. Usually it's bronze, but quite often it could be copper plates put in and they are held in under pressure usually.

The centre one covers iron staining and obviously, we have iron fixings, securing bronzes, two monuments, and frequently iron armatures within the bronze, and this often is the case with equestrian statues, where the bronze itself is not considered to be structurally strong enough without inserting at the time of making an iron armature within the object itself. And it also acts as the method of fixing it to the stonework. And on the right hand side this is a casting floor caused by shrinkage in the cast metal as it's cooling at the time of making. So these are all faults that you will find on bronzes and they can, because of the nature of them be the site for the initiation of corrosion.

Clara: Thanks Rupert. We’ll now move on to best conservation practice and conservation principles. These principles provide us with guidelines for best conservation practice, and you can see those four sort of that they set out there maximising the life expectancy of the memorial, while retaining as much of the original fabric as possible. That's a really important aspect when you're looking to do any repairs. Any conservation method should be the least interventive to achieve the desired aims. For example, using the least invasive cleaning method to achieve appropriate removal of soiling and any practical interventions shouldn't prevent the option for repeated or alternative future interventions. Sacrificial coating, such as lime washes, are retreatable, whereas the introduction of a consolidant is often more problematic. And conservation methods should only use materials which have demonstrated that they are appropriate to the original fabric. These are usually the same or very similar to the host material, and as we'll see this, this is very pertinent to metal and stone, but in reality each memorial will have its own unique problems which require unique solutions. And these must be based on the sound understanding of the current condition and careful consideration of treatment options, particularly with regard to their effect on the heritage values. And the challenges that these principles pose, not only for war memorials, but in other heritage structures is discussed in more length in part one.

David: OK, so just to try and classify some of the treatments and there's a list you can see on this slide and some of you may have spotted that consolidation has been omitted and this is intentional as the use of consolidants on war memorials is generally very limited and is. or should be, considered as an intervention of last resort so good practice requires that any treatment should only follow measures taken to mitigate the causes of decay, and this is really important that when we've observed and assessed and find out what's gone wrong.

Is there anything we can do to stop that happening again in the future? These are mitigation measures and they may be simple measures such as ensuring that water drains away or that overhanging trees are cut back, but it's certainly an exercise we need to go through. And then we have the treatments which can be classified under stabilisation, structural pair cleaning, biocide treatments repair, repointing, protection and renewal. And men are going to go through and look. Some examples of all of those particular themes. Stabilisation and structural repair.

Within the time frame of this webinar, is not really possible to go into detail on structural issues because they are usually very, very unique and pertinent to the memorial. Suffice it to say that corrosion of fixings, and ground settlement, are amongst the main causes and solutions normally require the input of specialist engineers.

Both of these images are taken from case studies that are available on the Historic England website, so I think Matt will be putting up the link to those. Cleaning, and this is really and, in many ways the most important element of war memorials. War memorials as we know are considered to be places of commemoration and respect, and therefore are unlikely to be heavily soiled because they will have been cleaned. In many ways, that's the problem, because there is an expectation that they should be clean and so regular maintenance cleaning is common and this reached ridiculous extremes with the cenotaph. It was cleaned every four weeks during the night and it's no surprise that whenever you see, if indeed you will see it this coming Sunday or Sunday week, that actually the stonework at particularly high levels of the cenotaph in is in a very, very bad condition in general. Every time the cleaning is carried out, the equilibrium that the surface has with its environment will be changed and the surface pores will become more exposed and the potential for enhanced decay increases.

So before cleaning, it's really paramount to know what we're trying to remove, so the appropriate method of removal can be chosen. So is it biological material? And in many cases, what appears to be a black cross can actually be just a build-up of biology. Is it pollution? Is it staining from iron ore or bronze? But also it's important to know why you want to remove it. Is it to allow increased legibility of the inscriptions? or because the soiling is damaging the surface? Or perhaps just to allow for better inspection?

All of these have to be set against the effect on the heritage values and the understanding that once you've started to clean something, there will be a pressure to keep it clean. And what are there going to be the longer term effects of that repeated cleaning? So it's imperative also to carry out trials and here the two images, you see on the left hand side is water cleaning with water and handheld brushes. And on the right hand side is the use of a DOFF superheated water system. So these are some of the guiding principles for cleaning stone of war memorials. Avoid anything with high pressure. It's unusual that you would find any situation where high pressure is going to help. Methods involving water are generally preferred, and I say that on the basis that quite a lot of the soiling that you'll find on war memorials tends to be biological.

Repeated cleaning, as I've already said, can be very damaging to stone, so we need to put in place a process by which it's not cleaned on November the 9th every year.

Operatives must be experienced in the use of the machinery and technique. I know, particularly, for local authorities, it may be easier to get a term contract are in just to give them a once over every November. This is not generally in the best interests of the of the war memorial. Superheated water methods such as DOFF and Thermotech are generally acceptable, but the pressure, the temperature, and the nozzle type must all be found out through trials and they must be appropriate to the problem and the type of stone. And you can see on the left hand slide there, that is somebody using a firm attack and not. It's very hard to photograph people using Thermotech because they are usually hidden by a cloud of vapour. In the middle, you can see dry steam cleaning which is using much less water and can be easier to see what you're doing. It's a bit slower, but it's certainly worth considering.

Finally, chemical poultices can be used, as on the right hand side, where a chemical poultice has been used for removing bronze staining. Very hard to get it completely removed, except by multiple applications of the poultice.

[They discuss a technical issue with sound levels for the recording]

David: So successful cleaning allows the aim of the cleaning to be achieved without harming the surface and while maintaining or even enhancing heritage values. And this is shown in these two pairs of photographs where the top one is just being gently cleaned and has managed to enhance the inscription and yet retained the sense of the memorial. The lower one actually has new inscription panels, but the way in which the surround has been cleaned ensures that the heritage values have not been compromised. This is you, Rupert.

Rupert: It is me, yes, and I think it's important just to make one point here. There is when we're talking about cleaning methods. There are two things that we might be talking about. One is cleaning as part of a restoration to put a memorial into good condition, or the metal work or model into good condition, and the second is cleaning as form of maintenance, whether that be yearly or every two years, for instance.

So I'm going to cover two things really dealing with both aspects. The most problematic thing with metals and war memorials is the collection of pollutants on the surface, which causes both the pitting corrosion and other forms of more aggressive corrosion, due to water runoff and everything else. But the accumulation of pollutant dusts which generally are hydroscopic and the rainfall which may or may not be acidic, can cause quite a big problem, which is why obviously we want to remove those particular things from the surface. And in that case then the use of superheated steam for the removal of pollutants and paints and varnishes and other things. And you have to remember with things like waxes and varnishes, they will also accumulate pollutants and waxes. Although they're very good are not completely impermeable to water, and certainly they will accumulate pollutants on their surface. So from time to time the removal of some of the wax you might put on the surface of maintenance. We might be necessary. The use of abrasives. If on bronzes would generally be frowned upon, whether they are war memorials or not. However, in instances where you've got the pitting corrosion, then localised use of abrasive for the removal of corrosion products or varnishes might be necessary. It's quite difficult to get these out. Or gentle hand cleaning, which is perfectly acceptable in certain areas and all I would suggest say is that these things used locally where necessary is all you need to consider. The use of chemicals is dangerous to be honest, very difficult to control, it will strip natural patina off bronze, and once a bronze has thirty years or so of unstable naturally formed corrosion surface on it, then the idea that you remove it and start again in is a very, very bad idea. You're basically removing it the surface from the bronze and all that will happen with lack of maintenance is that surface will start to reform again, so leaving it where it is definitely the best solution.

What we do about the green we will cover a little bit later on and there are also things like laser cleaning that have been tried on bronze are generally considered to be not very effective at differentiating between what is corrosion and what isn't it? So it would be very rare that I would advise the use of laser cleaning. So going back to the use of steam cleaning and/or other chemicals, and in instances where we have to remove paint or varnishes or waxes, then the use of high pressure steam, in conjunction, occasionally with eco-friendly paint strippers is the best way of dealing with this problem. And fairly simple to do, but as David has already mentioned, it does need some degree of expertise and understanding before you start to do this sort of thing and you have to remember that the wash off that you get in chemical terms and particulates from the surface coatings, of course, will potentially drop onto the stones. You need to be very careful to protect the surrounding material while you're actually undertaking a work like this.

Clara: Thanks, Rupert. We're now just going to look briefly at biocides. And although biocides might be seen as a suitable alternative to regular cleaning, neither Historic England nor the War Memorials Trust advocate the use of them in most cases. As well as the harmful environmental impact of the component chemicals, the effect is generally quite short term. We've also noticed that. on some occasions, repeated application can lead to staining. We are currently working with the Commonwealth War Graves Commission, supporting them in some research that they're looking into to a more sustainable way of cleaning their estate. They've got obviously a huge number of war memorials and grey stones to look after. Historic England is also currently undertaking research into alternative treatments of treating biological growth, which includes UVC treatment, essential oils, and enzymes. I think Matt will put just a link just to our website which will give you a bit more information.

The short term effect of biocides is perfectly illustrated in these two pictures here at the Royal Artillery War Memorial in Hyde Park Corner, where biological growth just keeps coming back. Biocides have been used, but as you can see here in less than a year, the green algae and biofilm is back with a vengeance and attempts to mitigate, as David mentioned, mitigating measures such as persuading Westminster councils to perhaps take down the trees that overhang the war memorial that proved unsuccessful. And the continual ongoing cleaning to maintain this memorial is eroding, due to this regularity of cleaning, if some of you with a BDI may notice that on the vertical relief carving. That was actually treated with Brethane in 1982 and there's no algae on that. So that's a very interesting point. David will now talk about some mitigation strategies that may be more appropriate.

David: Yes, thanks Clara, just worth mentioning on that Royal Artillery War Memorial, that the Brethane that was used to treat the relief carving contained a lead catalyst, which is why it's no longer available because it failed to conform to new Health and Safety standards. But the lead is still sufficiently active to prevent the growth of algae. In terms of examples of mitigation strategies, this is the Cheltenham Cenotaph, the main Cheltenham war memorial, which is a simple sort of obelisk design. It has over 1500 names, incised and filled with mortar. The design of the obelisk means that water runs over the inscription panels, encouraging the formation of by microbiology and thus obscuring the names. Repeated cleaning caused the stone surface to decay, and the letters to fall out, as you can see on the bottom left slide there. So faced with this issue, there are a number of alternatives, including accepting illegibility alongside public education for the causes, amending the cleaning regime, or altering the design. So after a good deal of justification, a stainless steel flashing has been installed above the inscription panel which you can see on the picture on the right and this deflects water from the inscriptions and means that the regularity of cleaning has been substantially reduced. And I should add that despite fears to the contrary, hardly anybody has notice the flashing. Clara.

Clara: Thanks, David and when it comes to repointing the choice of mortar will depend on many factors. And the mortar should aim to be sympathetic, not only to the colour and the texture of the stone, but should be more permeable to allow moisture to move through this rather than the surrounding stone. Mortar, which is less permeable than the surrounding stone will encourage it to deteriorate, so the stone will deteriorate rather than the mortar. Obviously the mortar can be replaced more easily. Also, depending on the type of stonework, if it is a more formal ashlar which you can see on sort of the two left hand side images there or perhaps on the right hand side and more random stone joints must be filled fully and the pointing joints of the mortar should be finished appropriately as well and packed in, and also tended to make sure that the mortar cures completely. We would advocate that the most suitable binder when doing mortar repair, sorry pointing, mortars should be aligned putty or a hydraulic line depending on the type of stone. And same in the case of mortar repairs.

Here you can see on the left hand side. There is an example ion the Royal Artillery War Memorial where very small repairs have been used to protect the stone and to stop water entrapment. On the right hand side. This shows the use of a proprietary mortar on the inscription panel, Aston War Memorial, you can see on the top image of the inscription, which is barely legible, and then on the bottom image you can see that the right hand stone there you can read, it's formed the inscription. And the properties of this particular mortar allow it to be applied in a very thin layer into which then the inscription can be cut. So the choice here to use a mineral mortar has improved the legibility of the inscription, when sharpening of the original stone isn't possible and replacing the section of that stone would be extremely disruptive. These mineral mortars which are often using a liquid binder of something, say like zinc hydroxy chloride. They also have various additives. They can be useful for specific situations, but we wouldn't usually think they would be suitable for general stone repair. David.

David: Stone was traditionally protected by limewash, but there are very few of any lime washed or painted stone war memorials. Instead, shelter coat, which is essentially an aggregated limewash, is applied and brushed well into the surface. You can see in the centre two images that there. The top one is the open texture of stone x 50 magnification, and the lower one is the same piece of stone, after the application of a shelter coat, whereby you can still see the characteristic sort of texture of the surface, but the pores have been filled. So by filling the pores of the stone, the accumulation of pollutants and, and the colonisation by microbiology on the surface can be reduced. As a result, there should be less need for regular cleaning. So on the left is a typical memorial with the recently applied shelter coat and on the right the Cenotaph, which has had shelter coat applied to all the stone above the upper offsets. We're just going to cover here an issue related to the use of wax. It is the traditional coating for bronzes and there is a difference between hot waxing and cold waxing.

The reason that we hot wax bronze is the patina layer, the natural patina layer or chemical patina applied by the particular foundry doesn't matter, is that porous surface. If you apply wax to that surface cold, it tends to sit on the surface of the bronze rather than actually soak into the porous patina. The hot waxing process makes the wax mobile and is absorbed into that porous patina layer, thereby offering it far more protection. The one result you will always get with hot waxing is it'll turn whatever colour your bronze happens to be darker hues, because of that absorbing of the wax. And it's perfectly possible, and in my view acceptable, to apply hot waxing over a stable natural green patina, without the need for any additional colouring technique.

There are obviously two several different techniques for colouring bronzes. You can apply a patina over the natural chemical Bettina in the same method that they would have done in the foundry. This can be applied over a green stable patina. It will just change its colour. And it is, in my view, the least interventive of any of the process. There are of course other ways of producing Browns on bronzes, one of which is to use pigmented wax, which are the two images in the centre and the right hand side you have to remember that using wax is impregnated with pigments, is that, to all intents and purposes, you are applying a paint again. And we have, obviously, some disagreement about the use of paint on normal war memorials, but it is a method that you can use. One of the problems is that patina it or waxed bronzes that you're trying to replicate a varied coloured patina means that you're mixing little areas of different colours of waxes together. Which is fine for the first treatment, but as maintenance goes on, especially if you have to use hot wax again, then of course you're going to be stirring those mixed pigments together and you will end up with a bronze that looks exceedingly flat and uniform in colour. And the same would apply to the use, for those of you have come across it, bronzing powders. They are designed there again using metal based pigments to rub into the surface of a bronze, over which you then apply wax as a treatment. But they both are additional pigmented coatings, and I think, if it's possible to use traditional techniques in the way that the foundry would have done in the past, it's preferential. And this is an example of that chemical patination.

So on the left hand side you have a stable green patina on a line and this was chemically patinated using potassium polysulfide, very weak potassium polysulfide, and that is turned green, brown and then that has been waxed. And it's a very, very stable colour and maintained in that way, and I would say that with most bronzes in outdoor environments, with the exception occasionally of some bad city environments, that once a bronze has been restored in hot wax well, then rewashing it, maybe yearly to remove pollutants, but certainly no more than every two years, would you need to apply another wax coating. And if you continue to do that there is no reason that that bronze will ever change colour again. And it will also obviously stop the dissolution of copper salts from the surface, causing problems for David and stone conservators. I think that's you David.

David:  So the enhancement of lettering is a common issue with war memorials and obviously needs to be approached with great sensitivity. The inscriptions are in most memorials the most significant element of the memorial. So enhancement can be done, depending on the type of inscription. So it might be very careful painting where paint is faded, gentle recutting of incised lettering, where the inscriptions have become less legible or insertion of lead letters where they're missing or regilding, all of which are illustrated here. But all of these interventions must be guided by good evidence or a record of what the inscriptions were. And that was covered to a certain extent in part one of the webinar where we outlined the rules for inserting new names as well as enhancing old ones. In terms of renewal, of course there are occasions when stone has to be replaced, and again, that requires great sensitivity. Because of the widespread loss of quarries over the past few decades, the selection of a matching stone can be very difficult, but there is some Historic England guidance, which again, I think Matt will magically make appear a link to it. And apart from the choice of stone itself though, which of course needs to reflect what was there originally. Joint widths and surface finish or are very important aspects that need to be addressed, so you need to have you know very thin joints and the finish you know need to reflect the adjacent stone and not be straight off the saw. So those are issues which you need to look at really when renewing stone. Rupert.

Rupert: Yes, got it there. Yes, there are occasions where replacement is required on the metal’s front usually due to vandalism and theft and both these examples are from the Bootle War Memorial, for which there is a detailed study for Historic England on that project itself, and in this case there was a gun strap that had been stolen. And luckily there were original bits of it left, so we were able to copy exactly the same material and the same design of the strap. And on the right hand side, the original bayonet was missing and there was a huge amount of research to work out which exactly Enfield gun and what size of bayonet it actually was. And after about four weeks of research, we decided that we had found the right Lee Enfield and right size and length bayonet. And that was made and put in. You can also see that it was originally put in using a ferrous fixing which split the handle of the bayonet it the grip of the bayonet. And in this instance, because of the theft problem, we've made the bayonet removal. So if you go to look at the memorial now, unless it's anywhere near a Memorial Day, you will find that this particular gun doesn't have a bayonet in it. It's only put in at the time that's the memorial being used as a commemoration. So replacement parts are very good, but as Dave has also said and Clara has reiterated several times also, the issue of research and record keeping is absolutely critical.

Clara: Thanks, Rupert, you’ll have heard various mentions of the word maintenance and we can't emphasise it enough. It's an essential part of caring for a war memorial. And here we've just listed some of the critical components of that regular inspection, which carried out by the local community who can easily keep an eye on any changes in the condition. That's really helpful, and keeping records of these changes through a simple condition survey. There is actually a template in the Historic England Wars publication, which is just a couple of sides, so it's very easy, easy to sort of make, take notes. Photographs, they are invaluable and these can easily just be sent to specialists and professionals to review, just to get an idea without you know the need of a site visit. Obviously, you know a more detailed condition survey. An investigation examination is something that we would suggest that specialist conservators are involved with. But then programming any practical intervention is important.

Simple tasks such as clearing loose debris, cutting back overhanging trees if we've seen, and removing weeds from around the War Memorial can be done by volunteers, but the upkeep of the war memorial itself is best undertaken by professionals. Rupert and David, you've mentioned about the importance of maintenance. But just to reiterate here, can you just give us your last views on maintenance for each of those metals and stonework group? Rupert, if you'd like to say.

Rupert: Yes, I'll go first. I've got a little list, so I'll almost read the list. I think I'm going to emphasise the importance of regular inspection and maintenance, and the scheduling of the requirements for any care regime that's found to be necessary. And there will also be very different regimes for metals and stone. So whereas a bronze might need washing and waxing once a year, the stone nightly cleaning every three years, and it's important to understand that to make sure that you get the best benefit of time and money. Obviously regular maintenance, keeping things in good condition is a very cost effective exercise in the long term, rather than undertaking a major restoration programme. The production of very clear maintenance specifications by the person that the company may have carried out the initial restoration for its care in the future with materials and techniques all identified.

Generally speaking, simple techniques and materials are definitely the best and it is with small memorials, not things like the Bootle Memorial. Obviously with small memorials, it may just mould a bronze plaque and it’s quite possible to produce the specification that could be done by volunteers with minimal amount of training. At least you have someone who cares for it, looks after it, records it and can alert anyone to any problems that occur and lastly, when major works are scheduled, i.e. that was the conservation restoration.

The work that the stone conservator will do to a war memorial, and those that one might do for metals are to be worked out quite often. Because this happens with this memorial i.e. that we’ve restored and rewaxed and dealt with all the bronzes on the monument. And then the stone mason decided to do a lot of stonework and ended up covering the bronzes in stone dust, which we had to spend another three days cleaning all the bronzes down again. The scheduling has part of works in really critical. David? David’s off.

David: I’d only add that stonework, as Rupert intimates, probably needs less regular intervention. But factors like checking on the condition of pointing, and possible reapplications of salt, will ensure that the stonework is not allowed to deteriorate to the point that major work is required and that is the point ultimately, the main element of maintenance, it is to keep doing a little bit often to prevent the major cost of large works occasionally.

Clara: Thanks, David and Rupert. I think the little and often is a really good phrase to use. So just to finish off, just to remind you. You will find more of our technical guidance on war memorials on the Historic England website. Also, there is a wealth of information on the War Memorial Trust website. We’ve got videos, technical advice, notes and case studies, so some of which we've mentioned here. And if you haven't already signed up for the technical conservation email then I would encourage you to do that. But thank you very much for your time today. Hopefully you've got a little bit of time. We've got a few questions so hopefully we can address some of those in the time we've got left.

Matt: Clara, David and Rupert thank you so much. Absolutely fantastic presentation. We do indeed have a few questions and I know we're running overtime. So to all of those who have to leave us now, many apologies. But do remember we have the recording that you can refer back to and the Q&A will be in that recording. So first of all, would it be appropriate to remove an applied patina (dark grey) that was introduced as part of an earlier treatment where the where the patina does not reproduce the artists or foundry’s original intent, nor the naturally occurring patina?

Rupert: I think the answer to that would be yes. As long as the historic references there of what the patina was like in the first place. I mean clearly if it is dark grey. It's unusual to have a dark grey patina. I'm not quite sure how that would be formed, but if it's dark grey, it is, and it's a bronze we're talking about, then I would suggest that is not appropriate, nor right. And so the recolouring of the bronze, whether it be by the use of chemical patinas over the top of a natural patina that's there, would be OK. One of the problems you would have is, if the existing bronze you're talking about that’s gone grey, is a chemical patina that has soaked into or converted natural patina. Then obviously the removal of it would be almost impossible, but if it's applied on top of what's already there, then I think the removal of it and the repatination/colouring of it to a more appropriate colour, brown perhaps, would be perfectly acceptable, yes.

Clara: I was just going to say, Rupert, that you mentioned they about you, it's important to understand what that Gray additional patina is and to understand what it is why you want to remove it, and then how you're going to remove it as well, isn't it?

Rupert: Absolutely yes. I mean, it will be. I can't think of a grey patina but if it is actually a patina and not an applied pigmented coating, then we definitely want to find out which it was, and if it worked and what it was made of and how it was applied, yes absolutely.

Matt: Thank you. OK, let's have another question. How would you remove rust staining from limestone? I think that one is for David.

David: Yes, it's a quite a regular problem because also a lot of the wreaths have wire enmeshed in them and, and they often rust and stain the stone. I know that's a regular problem at the Cenotaph. There are materials, there are specific poultices that you can obtain from suppliers, such as Stone Health or Restorative Techniques, which are iron removal poultices and they are chemicals that are applied to the surface and basically suck up the staining. A word of caution when using them, though they can quite easily overclean the stonework and so therefore you have a clean shadow of where you've been trying to remove the stain. But again things like concentrations and dwell times and how you rinse them. And all of those issues are things that need to be established through trials. But yes, that's the best method of removing the rust staining, if you use a lot of water, it can drive the rust further into the stone and which will then come out later on. So definitely a poultice which sucks out the stainers is the best option.

Rupert: Can I just add something to these? Quite often you do find rust standing on bronzes, either caused by core pins, iron core pins that have been left in the casting or rust emanating from the corrosion of armatures inside a bronze, and we would use the same again poulticed, either using these very locally applied poultices, using oxalic acid or thioglycolic acid, both of which form a nice poultice and will get rid of enough of the rust staining to make it treatable in terms of overpatination and/or waxing afterwards.

Matt: OK, another question, how often would you recommend condition survey inspection?

Clara: I would have said as we mentioned, if you've got a keen local community who are willing to take on some sort of regular monitoring, then a very basic sort of observational survey can be done on an annual basis. Calling in somebody to do a sort of full blown condition survey, I think, is something that can be done when you particularly go to a certain issue, but obviously those sort of things do cost money, so I think it's a combination of local community and willingness and enthusiasm, and good relationship with a professional architect, surveyor or specialist conservator. And just to sort of capture the question, from Colin, about the examples of regular conservation management and maintenance plans with regards to a typical war memorial, we don't have those specific to war memorials, but we've got a lot of information in the War Memorial guidance documents, and in part one we did talk about the care cycle and that whole process of setting up, recording, condition surveys, taking photographs and then planning that maintenance and work. So I would recommend that you have a look at Part one webinar. Have a look at our guidance document. Also practical building conservation basics that volume talks a lot about maintenance plans and conservation management, so there's lots of information there that can help you put something together.

Matt: And I've noticed also I've got the link there in the chat and that's for all the historic England videos on maintaining war memorials as well. One last question before we go: is rewaxing bronze once a year a reasonable regime, one for Rupert.

Rupert: Right, the answer to that is it's reasonable, and certainly in city environments probably necessary. However, if a bronze has gone through long periods of being maintained. You probably don't need to wax it every year. You might need to just wash it down with a little bit of very light detergent and water and give it a light buffing once it's dry and leave it alone. I'm against overwaxing things, but obviously you want to maintain the protective coating. We've looked after many, many memorials over the years and still do, and we would certainly say that in most cases where we've been looking after memorials for say twenty years that we now probably do it every once every two years. But it has very much to do with the environment and where the memorial is, and certainly if you're talking about coastal environments, I would say once a year would be very reasonable.

Matt: OK, and one very quick answer to this last question, what detergent would you use to wash a bronze?

Rupert: A simple non foaming household detergent. Occasionally it might be useful to use a detergent that you would find in a car wash if it's in a city environment where you get traffic film, which tends to be rather greasy and city quite difficult to remove. So a simple car wash type detergent is very good at removing things like that. Applied with just a hand spray and some very light low level pressure washing. And I mean low level. Obviously the issue, really, is making sure that you remove the residue, both residue detergent and all the material you're washing off so not only do you wash it off the bronze but then you have to wash it off the stone. Otherwise I'm just applying the pollutants that were on the on the bronze onto David’s stonework.

Matt: Thank you, OK, that brings this webinar to an end so you'll see here I put another window in front of in front of the slides. These are some links for you, webinars. If you click on the word webinars, you'll see the URL appear at the bottom of that window. That will take you to the webinar pages on the Historic England website, where you will find details of future webinars and links to the recordings from previous webinars. So the war memorials part one, you'll find there advice and guidance pages on the Historic England website. Again, all our advice and guidance are available there to download. And if you'd like a copy of today's slides, click on the on the title slides and again you'll see the URL appear at the bottom of the window there for you. At this juncture, it is for me just to say a huge thank you to Rupert and David and Clara for today's webinar. Absolutely superb. I hope everyone found it as fascinating and informative as I have. And to all our guests, thank you so much for your time today. I hope you found it as interesting as I did and we hope to see you all again very, very soon. Hopefully for next week's webinar, which is now up on the website and you can register. So I will mute our microphones now and leave the session open just for a couple of minutes so you can copy some of those links. At which points I will close the session. So thank you all for your time today and very good afternoon. Take care. All the best. Bye bye.