Working with glass Manchester Cathedral’s stained glass Conserving the Great South Window The greenhouse at Felton Park The long reign of Vitrolite No 177 September 2023 Institute of Historic Building Conservation
Working with glass Manchester Cathedral’s stained glass Conserving the Great South Window The greenhouse at Felton Park The long reign of Vitrolite No 177 September 2023 Institute of Historic Building Conservation CONTEXT 177 : SEPTEMBER 2023 1 www.ihbc.org.uk @IHBCtweet Registered as a charity in England and Wales number 1061593 and in Scotland number SC041945. Company Limited by Guarantee. Registered in England number 3333780. Registered Office: Jubilee House, High Street, Tisbury, Wiltshire SP3 6HA Officers President Mike Brown, president@ihbc.org.uk Chair David McDonald, chair@ihbc.org.uk Vice Chair Lone Le Vay, vchair@ihbc.org.uk Secretary Jo Evans, ihbcsecretary@ihbc.org.uk Treasurer Jill Kerry, treasurer@ihbc.org.uk National Office Director Seán O’Reilly, director@ihbc.org.uk Operations Director Fiona Newton, operations@ihbc.org.uk Consultations Coordinator consultations@ihbc.org.uk Administration Officer Lydia Porter, admin@ihbc.org.uk Professional Services Officer Michael Netter, services@ihbc.org.uk Membership Services Officer Carmen Moran, membershipservices@ihbc.org.uk Education,Training and Application Support Officer Anna Hart, training@ihbc.org.uk Committee Chairs Policy Roy Lewis, policy@ihbc.org.uk Membership & Ethics Andrew Shepherd, membership@ihbc.org.uk Education Chris Wood, education@ihbc.org.uk Communications & Outreach Dave Chetwyn, communications@ihbc.org.uk Branch Contacts North north@ihbc.org.uk North West northwest@ihbc.org.uk Yorkshire yorkshire@ihbc.org.uk West Midlands westmids@ihbc.org.uk East Midlands eastmids@ihbc.org.uk South south@ihbc.org.uk South West southwest@ihbc.org.uk East Anglia eastanglia@ihbc.org.uk South East southeast@ihbc.org.uk London london@ihbc.org.uk Scotland scotland@ihbc.org.uk Wales wales@ihbc.org.uk Northern Ireland northernireland@ihbc.org.uk Republic of Ireland republicofireland@ihbc.org.uk Rest of the World overseas@ihbc.org.uk Cover: The Hope Window in Manchester Cathedral by Alan Davis, with a statue of Humphrey Chetham (1580–1653), merchant and philanthropist (Photo: Alexandra Fairclough) See page 29 2 Briefing 3 The writer’s voice 4 Letters 5 IHBC North-West branch conference 7 Periodically 11 Editorial 14 The history of glass in the UK and Ireland Katia Papkovskaia 18 Conserving the Great South Window Jonathan Deeming 22 Environmental protective glazing Alison Gilchrist 25 Celebrating the everyday in stained glass Jeff Hopewell 29 The abstract stained glass of Manchester Cathedral Alexandra Fairclough 33 The wrought-iron greenhouse at Felton Park Edward Diestelkamp 35 The long reign of Vitrolite Katriona Byrne 38 Upgrading metal windows for thermal comfort Douglas Kent 42 Legal update 45 Notes from the chair 47 Director’s cut 49 Vox pop 51 New member 52 Book reviews 56 Inter alia 57 Products and services 60 Specialist suppliers index
Editor Rob Cowan Editorial Coordinator Michael Taylor, ihbceditorialboard@gmail.com Editorial Board Tom Copp Nigel Crowe Aimée Felton Peter de Figueiredo (book reviews) Rebecca Madgin Duncan McCallum Andrew McClelland Fiona Newton Gordon Sorensen Jonathan Taylor Michael Taylor (chair) Cartoons by Rob Cowan Context is distributed to all members of the Institute of Historic Building Conservation. © Institute of Historic Building Conservation 2023 ISSN 0958-2746 Publisher Cathedral Communications Limited, High Street, Tisbury, Wiltshire, England SP3 6HA 01747 871717 context@cathcomm.co.uk www.buildingconservation.com Non-member subscriptions to Context Context is available to corporate bodies at an annual subscription rate, including postage, of: United Kingdom £60.00 Elsewhere £90.00 Context on-line archive Past issues of Context can be viewed on the IHBC website. The archive provides a searchable database and reference for key articles. See www.ihbc.org.uk/page55/ context_archive. The views expressed in Context are not necessarily held by the IHBC or the publisher. Neither the publisher nor the IHBC shall be under any liability whatsoever in respect of contributed articles. We gratefully acknowledge the support of firms whose advertisements appear throughout this publication. While every effort has been made to ensure that the information contained in this issue of Context is current and correct, neither the IHBC nor the publisher can be held responsible for any errors or omissions which may occur. Context themes and copy deadlines Context is published four times a year in March, June, September and December. The next three themes and copy deadlines are: Rural buildings, December, issue 178 (6 October) Hadrian's Wall, March, issue 179 (22 January) Built and natural environment interface, June, issue 180 (22 March) Please contact Michael Taylor at ihbceditorialboard@gmail.com to discuss any editorial submissions or for information about the Context editorial board. 2 CONTEXT 177 : SEPTEMBER 2023 Briefing Support for heritage development trusts The National Lottery Heritage Fund and Architectural Heritage Fund (AHF) have announced a three-year partnership programme, building on AHF’s pilot heritage development trust initiative. This supported seven trusts across England with revenue funding, grants to develop plans for historic building projects and specialist advice as they scale up their activities. The new long-term partnership will expand the current heritage development trust programme across the UK. It will cover a range of organisations, from small volunteer-led trusts looking to An on-site workshop discussing the future of Pop Recs in Sunderland. The Tyne and Wear Building Preservation Trust has transformed the former pop-up record store into a coffee shop, music venue and bar. (Photo: Sally Ann Norman) The former Lancashire and Yorkshire Bank in Bacup has been restored as a co-working hub and residential apartments by the heritage development trust Valley Heritage. (Photo: Catherine Smyth Media)
CONTEXT 177 : SEPTEMBER 2023 3 expand, through mid-tier trusts with the potential for growth, to well established, larger trusts that are looking to make a larger impact in a particular community, place or wider area. The new heritage development trusts will receive a package of funding that includes threeyear revenue grants between £55-£70,000 a year. Included is guidance from consultants and mentors to develop their skills and knowledge alongside peerto-peer support to expand their network of contacts, with regular events to share expertise and experience. They will be eligible to apply for project viability grants and project development grants to help bring historic buildings back into use. Established trusts will be supported to grow a pipeline of projects and expand their portfolios. Additional support will be given to develop the skills of volunteers and established groups. The new programme is looking to support heritage development trusts to develop portfolios of historic buildings from which they can generate income. This ensures these important trusts become resilient and financially sustainable. Reconnecting Beckford’s tower Beckford’s Tower, currently on the Heritage at Risk Register, is to be restored by Bath Preservation Trust, with support from the National Lottery Heritage Fund, Historic England and others. Emery Brothers is the contractor. Completed in 1827, Beckford’s Tower was intended to house the collections of books, furniture and art of writer and collector William Beckford (1760–1844). Having sold the gothic-revival Fonthill Abbey in 1822, Beckford relocated to Bath and began the construction of his tower on Lansdown Hill. Riding out from his townhouse in Lansdown Crescent every morning before breakfast, he enjoyed the quiet of the tower and the views from the belvedere at the top. The ‘Our Tower: reconnecting Beckford’s tower and landscape for all’ project will transform the museum, open up the landscape and provide a new learning programme. Beckford’s wealth was secured from his ownership of plantations and enslaved people. The project will enable better interpretation of Beckford’s story based on wider exploration of his connections with the transatlantic slave trade. Beckford’s Tower: looking up From The Seven Lamps of Architecture by John Ruskin (1849) The idea of self-denial for the sake of posterity, of practicing present economy for the sake of debtors yet unborn, of planting forests that our descendants may live under their shade, or of raising cities for future nations to inhabit, never, I suppose, efficiently takes place among publicly recognized motives of exertion. Yet these are not the less our duties; nor is our part fitly sustained upon the earth, unless the range of our intended and deliberate usefulness include, not only the companions but the successors of our pilgrimage. God has lent us the earth for our life; it is a great entail. It belongs as much to those who are to come after us, and whose names are already written in the book of creation, as to us; and we have no right, by anything that we do or neglect, to involve them in unnecessary penalties, or deprive them of benefits which it was in our power to bequeath. And this the more, because it is one of the appointed conditions of the labour of men that, in proportion to the time between the seed-sowing and the harvest, is the fulness of the fruit; and that generally, therefore, the farther off we place our aim, and the less we desire to be ourselves the witnesses of what we have laboured for, the more wide and rich will be the measure of our success.
4 CONTEXT 177 : SEPTEMBER 2023 Risks of fast adoption From John Fidler, Marina Del Rey, California I was interested to read John Preston’s rendition of the decisionmaking and impacts of the scheme to clad the lead roofs of Kings College Chapel with photovoltaic cells (‘A world-wide precedent for solar panels?’ Context 176, June 2023). I greatly admire and appreciate John’s dedication and tenacity in the cause of appropriate energy conservation for historic buildings. This case must feel very depressing and issues a challenge to all of us similarly concerned. A few points and queries that follow on from his explanation of the case: 1. The subjectivity in the phrase ‘less than substantial harm’ surely needs to be addressed more aggressively by Historic England and its legal advisers through illustrated guidance and robust argument. This is otherwise a very large loophole for local planning committees to wriggle through to get what their politicians want. It seems that every planning and listed building consent application I have seen recently admits to the concept of harm, but dodges the bullet on substantive or degree of harm. Where is the detailed published weaponry for conservation officers on balancing heritage harm versus other socio-economic benefits? 2. What carbon offset was offered by the applicants with respect to the PV panels themselves? Many forms of PV panel are made via a dipping process, the chemicals from which are ozone-damaging. 3. What will be the physiochemical impacts of the PV arrays standing on top of the leadwork? The arrays will place the lead sheets under them in the shade, out of the sun, and the lead will therefore be colder than previously at night and over winter periods. Rainwater running over the surface will keep sheets wetter for longer without the otherwise hot daytime surface temperature drying them off quickly. What impacts will these circumstances have on new lead patination/corrosion, and condensate issues so far as thermal pumping and underside lead corrosion are concerned? Is anyone investigating these issues? Fast adoption of new technologies can have unforeseen risks. John Fidler Look out for faulty concrete From Charles Shapcott, conservation accredited engineer The civil and structural engineering watchdog CROSS (Collaborative Reporting for Safer Structures) UK has highlighted concerns with precast concrete floors and roofs made of reinforced autoclaved aerated concrete (RAAC). The material was marketed as being good at insulating roofs and floors, being a foamed concrete similar to early Thermalite walling blocks. A paper describes the difficulties experienced in service with RAAC roof planks on structures designed and built from the 1960s and finished before 1980. The units are about 600 mm wide and were dry jointed with smooth soffits, before the application of any surface finishes, sometimes painted direct. The trade Letters names of two manufacturers are Siporex and Durox. The defects prior to a major failure comprise excessive deflections and cracking, also identified in a number of roof planks, and there is evidence of the start of reinforcement corrosion. A roof with minimal falls may experience ponding in the middle of the span, increasing the loading above acceptable levels. Any water that gets into the material, through leaks, will be held there, unable to dry out, corroding the reinforcement. Certain chemicals that were used in the hydration and foaming of the concrete can be enlivened by unintended water being in the final matrix as built. Inspecting architects and others should look out for this type of construction during their quinquennial inspections. There have been more than 900 failures of RAAC planks in schools, hospitals and municipal buildings within the last few years, and this material may well have been used elsewhere. Charles Shapcott Since Context received Charles Shapcott’s letter, the risks of RAAC failure have been prominent in the national media. Proper governance From Richard Griffith RIBA RIAS Local authorities issue over 30,000 listed building consents each year. Those consents directly affect something like £2 billion worth of development. Yet the performance and effectiveness of listed building control are not measured at all. The control lacks even a single measured protection standard. There is no official explanation why listed building protection is not subject to measured regulation. There is no significant reason for its absence, and there are very significant reasons for its introduction. A straightforward framework of measured guardrails could be introduced without difficulty and without incurring any additional burdens at all for local authorities. Isn’t the introduction of proper governance long overdue? Richard Griffith
CONTEXT 177 : SEPTEMBER 2023 5 IHBC NORTH-WEST BRANCH CONFERENCE Adapting heritage to climate change At its conference ‘Adapting to Climate Change: heritage and its sustainable future’ in Chester Cathedral in April, the IHBC North-West Branch challenged Historic England to find common ground between conservation architects looking to place historic buildings at the centre of the climate challenge and conservation officers uncertain about the impact of change on listed buildings. Tony Barton, chairman of Donald Insall Associates, hosted the conference and opened with two messages he had received on the same day. A Grade I listed building in Yorkshire had received permission to replace its windows with double glazed units, yet pre-app advice for a Grade II barn conversion was that replacement glass should be single glazed. ‘Where are we?’ Barton asked Historic England’s strategic head of climate change, Clare Hedley. She responded that policy advice was forthcoming, in the form of a new Historic England advice note ‘Climate Change’, due later this year. Tim Stratford, the Dean of Chester, a scientist in a previous life, gave the conference sobering facts on the economic realities of heating and lighting the cathedral. Electricity and gas consumption had reduced by 15 per cent and 40 per cent respectively, but energy costs had nearly doubled. Staff had been provided with heated jackets and walking visitors were warm. But, as the conference discovered, sitting for any length of time was uncomfortable in a largely unheated cathedral. The cathedral plans to use two historic spaces for conferences Chester Cathedral, the ‘largely unheated’ venue for the IHBC North-West Branch conference (Photo: David Iliff, Wikimedia)
6 CONTEXT 177 : SEPTEMBER 2023 and events. These will be vital to its income but it would involve secondary glazing to the stainedglass windows. Were the heritage authorities ready to even consider this yet, Stratford asked, when the cathedral was still in discussions about whether it could have a glazed draughtproofing screen to one of its entrance doors? Hedley responded that Historic England was promoting England’s historic buildings as part of the solution to the climate emergency, and that architects and conservationists alike were good at managing change. She accepted that the planning system, as it stood, could make this difficult, but that advice on mitigation and adaptation to help tackle the climate emergency was imminent. She said that Historic England believed that every building could be made more energy efficient but acknowledged that this could be uncomfortable for some conservationists. She likened the need for change to the previous generation’s, largely successful, drive for equality of access into historic buildings. Jane Entwistle, recent past president of the Institute of Structural Engineers, gave a perspective from other climates where resilience against increased wind and rain are the challenge. The UK’s buildings, including Chester Cathedral, were also being adapted to cope with heavier summer downpours, a tangible result of climate change. News from the front line came from Sophie Norton of the Carbon Co-op. She described an inspiring community based project in Levenshulme, Manchester, where traditionally built houses are taking a ‘fabric first, whole house approach’ to insulate, draughtproof and secondary double glaze family homes. Norton explained that in addition to the lack of any financial assistance, the real challenge was training operatives and installers within the PAS2035 model, but that the co-op was delivering its target of a minimum EPC ‘C’ rating for traditionally built buildings. The danger of historic buildings being stranded by their inability to gain viable EPC ratings for the rental market was one of the drivers behind the current Grosvenor and Insall research project in rural Cheshire. Joby Howard, Grosvenor’s director of buildings services, explained the group’s published commitment to meeting the climate challenge. He said that Grosvenor had collaborated with Donald Insall Associates on a rural property, which was currently under construction, following detailed research and analysis. This was a pilot project to inform how their rural estate could both meet the climate challenge and maintain economic viability. The design options had been carefully assessed against climate impact, cost, buildability and attraction to the rental market. Insall’s analysis had been aided by Diane Hubbard of Green Footprint. She explained the iniquities of the current EPC system but said that the project was showing a 65 per cent improvement in carbon emissions, which was increased to 85 per cent if embedded carbon were to be added for the lifespan of the house. Hubbard summarised that: • EPC assessments were not fit for purpose. • In-situ tests proved that historic buildings performed better than expected from U-value calculations. • Training and improving installer skills were key factors for success. • The research project showed that the commercial aspects could be met. Tenants had already signed up for the house and would contribute to the monitoring of the project and aid further research. Grosvenor and Insall have also collaborated on policy issues. Insall’s Cordula Zeidler, practice director and historic building consultant, gave advice on how policy and regulation interacted and conflicted. She asked how policy guidance could be followed in practice to meet the UK’s climate targets, and whether low carbon mitigation measures were defined as ‘harm’ in the National Planning Policy Framework. Zeidler pointed out that Chester Cathedral had installed photovoltaic panels and that Kings College Chapel, Cambridge, also had consent, despite opposition from the conservation authorities. Heritage partnership agreements and local listed building consent orders were good tools to enable consents for the necessary improvement to historic buildings. The skills of architects working with conservation officers and Historic England, within an agreed statutory framework, could enable listed buildings more easily to meet the challenges of the climate emergency. This was now a standard procedure, in Kensington and Chelsea, for example, and Zeidler asked that professionals listen to the strong public feeling for thermal improvements and carbon mitigation to be made easier to achieve. Max Fordham’s Gwilym Still gave a technical briefing on what current technologies could offer in changing older buildings, including mitigation of overheating in summer. He stressed the need for careful research and modelling, allied to basic building maintenance. Great strides had been made in air handling in recent years. Still demonstrated how space heating could run at lower temperatures and explained the factors to be considered when specifying heat pump technology. As well as paying for high quality design, clients must be thoroughly trained on how to properly control their systems. The panel summed up the conference’s key points for government: • totally revise the EPC system • align the planning system to sensitive climate-change mitigation through the NPPF • invest in bridging the skills gap • give financial incentive by abolishing or reducing VAT on thermal improvements to traditional buildings.
CONTEXT 177 : SEPTEMBER 2023 7 Periodically The IHBC encourages members to read widely to accumulate expertise and technical knowledge as a contribution to their CPD. Your reviewer encourages readers of this column to range widely in furtherance of that aim. SPAB Magazine One of the perennial intractable problems faced by practitioners is that of the energy performance, upgrading or replacement of traditional windows. Incorrect choices will result in buildings losing much of the character, beauty and historic interest, but doing nothing is no longer an affordable or socially responsible option. In the summer 2023 issue of the SPAB Magazine, Marianne Suhr discusses ways to reduce heat loss and eco-proof listed dwellings without detriment to the heritage value or the climate. While there can be no excuse for removing an old window with historic significance, the key question Suhr poses is what should be put back when the window to be replaced is genuinely beyond repair? Many historic building professionals remain fixed on the idea of single glazing secured with traditional linseed oil putty as the only option for an old building. Conversely the green lobby, in pursuit of passivhaus standards, has long since moved on to triple glazing in the quest for carbonneutral buildings. Suhr notes that many homeowners concerned about energy conservation regard replacement windows as quick wins. Her stance is that there is no one-size-fits-all solution, as each sash or casement window needs to be looked at for its age and significance; its orientation; its condition and crucially, its pattern of use. Only from this level of understanding can a sensible strategy to reduce heat loss be understood. She rightly identifies the frustration of being unable to find skilled carpenters who can carry out careful in-situ repairs without breaking any old glass, and a decorator to properly remove all the flaky old paint to give the repainted joinery a reasonable chance of longevity. These seem increasingly to be big asks. The article also looks at secondary-glazing issues, and highlights that when upgrading old windows, draft-proofing alone is no longer adequate as this does not address the loss of heat by way of conduction through the glass. The article precedes a conference on the future of historic windows at Warwick University in September, the outcomes of which may be reported later. Elsewhere Christina Emerson, head of casework at SPAB, gives the society’s view about the controversial proposals for the application to install solar panels on the roof of Kings College Chapel, Cambridge (which John Preston addressed in Context 176, June 2023) and states the conservation principles underpinning the SPAB’s concerns. As part of its technical role, SPAB recently called for evidence regarding buildings that have received colourless hydrophobic water-repellent treatments, so that researchers could visit the sites to gauge whether this has met with apparent success or where subsequent problems have been identified. The results will be awaited with interest. THE SPAB MAGAZINE SUMMER 2023 FALERONE, ITALY Post-earthquake recovery and regeneration MEMBER REPAIR PROJECT Conserving a Georgian house in Kircudbright BUILDING IN FOCUS Stoke’s former Free Public Library Exploring eco-solutions Historic windows A window at Sissinghurst Castle, Kent (Photo: Rob Cowan)
8 CONTEXT 177 : SEPTEMBER 2023 The Georgian The Georgian (Issue 1, 2023) continues to highlight identification of historic architectural fixtures drawn from the Charles Brooking Collection. The sixth instalment looks at hob-fire grates and once again is splendidly illustrated. Where such grates survive in-situ, this article will help practitioners more accurately date Georgian and early Victorian buildings. Also of note is an nicely illustrated article by Nigel Hankin, an archival volunteer for the Georgian Group, who shares his research on ‘Egyptian taste’ in Georgian England. Chrissie Paver, head of marketing and communications at Painshill, explores the development and restoration of this important landscape garden, currently attracting around 200,000 visitors a year. Much of the restoration work followed the establishment of the Painshill Park Trust in 1981. The author points out that there are still many management challenges. Climate change means that the park is increasingly subject to flooding, bridges have been damaged, and the ongoing upkeep and restoration have become more difficult to sustain financially. C20 Underrepresented building types in the statutory list continues to surprise. The first 2023 issue of C20, the magazine of the Twentieth Century Society, highlights this by way of an exploration of 20th-century fire stations. Billy Reading’s illuminating article sets out a potted history of this building type and a plea for greater recognition of its merits. Illustrations, drawn from a wide range of locations, cover the earliest extant 20th-century examples and the architectural treatments of the 1930s. Reading examines the technological innovations regarding architecture for firefighting; the impact of the second world war on fire services; and further post-war changes. These and other aspects are also covered in the author’s recently published book Fire Stations (Britain’s Heritage). The appropriate upgrading of important 1970s modernist architecture can be a challenge. Catherine Slessor reports on the completion of the £68.25 million six-year refurbishment of Glasgow’s much-admired Burrell Collection. Barry Gasson won the original architectural competition. Slessor assesses whether the recently completed works have preserved the original magic, and in a what-if moment wonders how things might have turned out if second-placed Denys Lasdun’s pre-cast concrete pavilion, topped by a tinted glass space frame, had won instead? Local authority housing is rarely the focus of heritage management, but John Boughton’s thoughtprovoking piece about the concept of well-designed council estates has brought this back into focus, based on his RIBA-published book A History of Council Housing in 100 Estates. Perhaps more schemes should be listed. Catherine Croft’s endpiece about conserving estates ‘What works – and what doesn’t’ highlights the key to conservation as finding sympathetic, affordable ways to upgrade thermal performance without destroying what makes the estate significant (and subject to heritage protection). Well worth noting in this issue is a celebration of the work of an unsung army of architectural model makers that helped to shape ideas about 20th-century Britain, with some very striking examples of their work. Many of the examples are very ambitious and unrealised projects, including a pretty staggering 1972 proposed obliteration by Richard Seifert of Liverpool Waterfront. Heritage Now The summer issue of Heritage Now (02/2023) provides some well-illustrated lessons regarding sensitively improving accessibility, functionality and energy efficiency in the Grade I listed Porter’s Lodge at Exeter College, Oxford (built between 1671 and 1710). Elsewhere, Alan Calder, the biographer of Edward Guy Dawber (1861–1938), draws attention to three of his finest buildings away from the Cotswolds (with which he has generally most Head of Persephone (c420 BCE) in the Burrell Collection (Photo: OSM Amin, Wikimedia)
CONTEXT 177 : SEPTEMBER 2023 9 been associated) near Salisbury and Matlock, and in Dorset. The issue also looks back at the 70-year publishing history of the Ancient Monuments Society Transactions (now continuing as the Journal of Historic Buildings and Places); and Paul Holden is in conversation with Frank Kelsall and Timothy Walker about their new book Nicholas Barbon: developing London, 1667-1698. Journal of Historic Buildings and Places While on the subject of the Journal of Historic Buildings and Places (incidentally, one of the great benefits of membership), the latest issue (Vol 2, 2023), running to 166 pages, reflects the role of the society in campaigning for buildings of all periods. Subjects range from the 14th-century Clevedon Court, Somerset, to a reconsideration of the Victoria Centre shopping megastructure, Nottingham, on the 50th anniversary of its opening, and the loss by fire in 1994 of the late1950s Norwich Central Library. These cases help provide a context for the buildings that were considered worth campaigning for at the start of heritage protection; ones now lost to us; and those of the modern era that might justify a re-evaluation in the light of heritage protection reform, particularly where evolution in response to commercial and other pressures may have devalued the special architectural or historic interest to the point of denial of protection. In the case of Clevedon Court, it was the efforts of the owner to save his family home from probable demolition shortly after the Historic Buildings and Ancient Monuments Act 1953 came into force. Shortly after, the Historic Buildings Council for England (a department of the Ministry of Works) was established, and Clevedon was one of the earliest test cases for its operation and the effectiveness of the new Act. This involved tortuous negotiations over a further six years (also involving the SPAB, the National Trust and the Treasury) as they all juggled conflicting requirements and priorities. The chronicling of this case puts into perspective evolution of statutory protection and more recent heritage protection reforms, some parts of which are perhaps now taken for granted. The lost Norwich Central Library is a particularly interesting post-war case. The received view of the building was that it was banal, brutal and ill-favoured. But it should perhaps be considered in the context of the 1959 report of the Committee of Public Libraries, and procurement within the social and political auspices of the postwar welfare state. That might prompt reflection of other difficult buildings of that era. Particular attention in this issue of the journal should be paid to the paper by Pete Smith, formerly a senior architectural investigator with Historic England. He provides (possibly) the definitive illustrated history and lengthy gazetteer of balconies or pergolas in 17th-century England. The paper looks at their architectural derivation and their Italian origins, and lists the locations of 198 balconies on 128 buildings. Georgian Group Journal Having referred to The Georgian, it would be remiss not to also mention the splendid annual Georgian Group Journal (Vol 31, 2023), another great benefit of membership of the group. Over its 190 pages, 14 papers are divided into three sections, examining town houses of the aristocracy; estate development; and late Heritage now The Magazine of Historic Buildings & Places | www.hbap.org.uk (02/2023) SUMMER 2023 CeLeBrating Heritage in aLL itS riCHneSS anD DiVerSitY Cleveden Court, Somerset (Photo: Celuici, Wikimedia) Norwich Central Library on fire in 1994 (Photo: mira66, Wikimedia)
10 CONTEXT 177 : SEPTEMBER 2023 Georgian and Recency London. Particular highlights include India Wright’s erudite analysis of the redevelopment of the Middle Temple following the Restoration; Iain Black’s insightful evaluation of the rebuilding of Martins Bank by George Dance the Younger between 1791 and 1795; and Gillian Williamson’s informative paper on overlooked aspects of life and lodgings in Georgian London. Journal of Architectural Conservation Two papers are worth highlighting in the latest Journal of Architectural Conservation (Vol 29, No 1, March 2023). The first, by Hadas Rix and Steven Emmett, looks at issues of authenticity when conserving historic imitative crafts, particularly scagliola, Coade stone, marbling and graining, where their unique and original use was promoted and articulated between the end of the 16th and 19th centuries. The authors emphasise that the conservation of such materials can be compromised without a nuanced specific approach. They set out the fundamental differences between artificial materials and the imitation of surfaces to inform guidance for conservation policy. They make a good case for the skills of imitative crafts being protected to retain their cultural significance. The second paper of interest, by Kate Jordan, is entitled ‘Victorian values, past and present, in the refurbishment of London’s historic churches’. The paper commences by looking at the influence of The Ecclesiologist on the restoration of countless medieval churches over the 19th century, ultimately leading to the foundation of the SPAB. Jordan suggests that a number of recent church re-orderings in London illustrate a great shift away from orthodox conservation principles towards creative restoration. The paper explores the factors that are influencing new approaches to church refurbishment, reading these against 19th-century debates on conservation and restoration. This is a particularly interesting paper for those involved with ecclesiastical work. Construction History Lucie Clarke discusses the heritage significance of building services in her article on the installation and impact of artificial lighting at Hatfield House, where Lord Salisbury adopted gas and electric lighting in the late 19th century. This appears in Construction History, the international journal of the Construction History Society (Vol 38, No 1, 2023). The author draws on previously unpublished archival records to explore the complex role played by Hatfield’s owner who, renowned for his interest in science and technology, was personally involved with the works to the house, setting him apart from the vast majority of his contemporary aristocratic landowners. Clark attempts to answer questions as to how the owners of great country houses went about installing new technologies, and the effect of such efforts on the fabric of the buildings. The Historic Environment The latest issue of The Historic Environment: policy and practice (Vol 14, No 2, 2023) concerns itself principally with the heritage implications of the invasion of Ukraine by Russia. The papers deal with issues such as the archaeological monitoring of war-torn Ukraine, contested heritage, and the reluctance of the USA to accept the terms of the 1954 Hague Convention. On a UK-related note there is a paper by Richard Newman entitled ‘Lest We Forget: the archaeology of warfare, conservation, interpretation and engagement in Hull and the East Riding of Yorkshire’. This explains the significance of conflict archaeology, the legacy of bomb damage in Hull and continuing community engagement. Bob Kindred MBE CONSTRUCTION ____ Volume 38, No. 1 2023 CONSTRUCTION HISTORY International Journal of the Construction History Society Vol. 38 No. 1 (2023) CONTENTS Editorial Inge Bertels, Nicholas Bill, Michael Chrimes, Sarah Melsens, Yiting Pan, Hermann Schlimme, Christine Wall and David Yeomans i Corrigendum David Yeomans 1 The installation and impact of artificial lighting at Hatfield House: Lord Salisbury’s adoption of gas and electric lighting in the later nineteenth century Lucie Clark 3 A progressive and pragmatic solution for Cape Town: the context and realisation of the first Steenbras Dam 1917-1921 Kevin Wall and Arne T. Singels 27 Edgar Cardoso’s bridge at Quiamafulo, Angola. Design and construction in the late 1950’s of the third road viaduct across the River Cuanza José Luís Possolo de Saldanha 49 Advanced technologies and people’s creations: the politics of concrete bridge construction in China, 1964-1978 Yichuan Chen 73 Bridging the gap: Engineer Eduardo Torroja in the post-war networks of Modern architecture Ramon Graus 99 Seabees in Rota. Platform frame in prefabricated housing in Spain in the 1960s María del Pilar Salazar Lozano, Antonio J. Cidoncha Pérez, Fernando M. Alonso Pedrero 117 Book Reviews Building a profession: a history of general contractors in Belgium (1870-1970) by Jelena Dobbels Survey of London: Vols 54 and 55 – Whitechapel by Peter Guillery (Editor) Eiserne Eremitage. Bauen mit Eisen im Russland der ersten Hälfte des 19. Jahrhunderts. by Sergej G. Fedorov, Bernhard Heres, Werner Lorenz, Karl-Eugen Kurrer (Series Editor) 139 142 145 HISTORY____ International Journal of the Construction History Society CONSTRUCTION HISTORY Volume 38, No. 1. 2023
CONTEXT 177 : SEPTEMBER 2023 13 WORKING WITH GLASS Opposite: The Flight window and Trinity reredos (stained glass, and oil on wood, both by Mark Cazalet) in Fraser’s Chapel, Manchester Cathedral. See page 29 Editorial Where aesthetics and technology meet ‘That’s strange,’ she said. ‘I’m sure the architect assured us that the glass extension would be invisible.’ Such comments are often heard when a significant amount of glass has been used in adapting a historic building. The use of glass as a material for roofing and walling is relatively new. How such glass looks will depend on what sort of glass it is, how it is designed and detailed, and how the building is lit from within and without. In some circumstances glass can be almost invisible or transparent, but usually one can see both the material itself and its reflections. Its particular characteristics can make it successfully complement a historic building when designed by someone who understands the material and its potential for constructing roofs and walls. For most of history, glass in buildings has meant windows. If modern glass is more than just glass, historic glass is also more than just glass. What the glass looks like from the outside and inside will depend on the technology with which it was made, whether cylinder, crown, plate, sheet, float or any other type of glass. That is part of the reason why it can be important to conserve historic glass, or to reglaze windows that have lost their glass with a historically appropriate replacement. Will anyone notice? Some will, and others will enjoy the building more without knowing how much its glass is contributing to its character. Glass rarely survives a change of window (unless it is so valued that, as in the case of Canterbury Cathedral’s Great South Window, featured on page 18, fragments of ancient glass were reinstated in the past). Windows are among the most changeable features of a building, facing us with questions of when to conserve or replace, and what glass will be appropriate for the building. As Historic England advises, before we decide what to do, we need to know the form, materials and history of the windows, their significance and the impact of proposed changes. Windows, like doors, are celebrated in architecture as the elements where inside and outside meet. That aesthetic function complements the practical ones. In addition to lighting the interior and providing views out, glass can let too much heat in, or too much heat out; and it will help to determine how much energy is used in constructing or adapting a building. As ever with historic buildings, glass is where aesthetics and technology meet.
14 CONTEXT 177 : SEPTEMBER 2023 KATIA PAPKOVSKAIA The history of glass in the UK and Ireland The texture, nature, patterns of imperfections and subtle hues of historic glass derive from the variety of techniques with which the material has been made since the 13th century. Where historic glass survives in old buildings, it is often an inseparable part of their character and history. Visually, the glass bends the light, transforming the interior and gently distorting the views out from the windows. Historically, the texture of the glass, the nature and patterns of its imperfections and subtle hues of colour tell the story of how and when the glass was made, while the size and quality of the panes can hint at the wealth and social status of the past owners. Between the 13th and mid-20th centuries, glass manufacture in Great Britain and Ireland was a complicated craft requiring the firing of precise quantities of materials in large furnaces under harsh conditions. Depending on the variations in the glassmaking technique over time, molten liquid glass was blown, spun, pulled, polished, ground and cut to make increasingly larger and more affordable window panes. The processes gradually improved to reduce the imperfections and achieve a consistent colour, texture and thickness, culminating in the fully mechanised manufacture of modern clear float glass on an industrial scale in the 1950s. Window tax Until the mid-1800s, glass and window taxes made glass an expensive commodity. In Britain, windows were taxed from 1696 to 1851, and glass was separately taxed from 1745 to 1845. Cylinder glass being blown in the workshop of Glashütte Lamberts, Germany (Photo: Glashütte Lamberts) The characteristic radiating ripples of crown glass in a window at Trinity College, Dublin (Photo: Graham Hickey) Window tax was levied in Ireland from 1799 to 1822, and glass from 1825 to 1845. Glass tax was calculated by glass weight and window tax by the number of windows in a property. In addition to the taxes, the Crown controlled
CONTEXT 177 : SEPTEMBER 2023 15 WORKING WITH GLASS the import and export of glass from other countries, including Ireland, which had a flourishing glassmaking industry in the 17th and 18th centuries. In 1746, export of all glass from Ireland was prohibited, with import allowed only from Great Britain. Further duty on Irish glass in 1825 effectively shut down any remaining glasshouses.1 Improved cylinder glass, produced in Britain from the 1830s and widely exported, was never made in Ireland.² The abolition of window and glass taxes in Britain coincided with improvements in cylinder glass technology in the 1850s, which reduced manufacturing costs and allowed for larger sheets of glass to be produced. The availability of larger panes, and therefore larger windows with fewer glazing bars, greatly impacted the appearance of the Victorian buildings, and made large glass structures like conservatories and glasshouses affordable to the emerging middle class. What is glass? Window glass was historically made by firing a measured mixture of sand, flux (plant ash) and lime. Incidental or intentional presence of metallic oxides in the mix can offer glass various hues of colour. Glass must rapidly solidify from its hot fluid state to become clear and prevent formation of visible crystals. As it begins cooling, glass becomes viscous and can be shaped, followed by further slower cooling to reach its final solid state. Broad sheet glass, also known as broad cylinder glass, was the earliest type made in Great Britain and Ireland. It was manufactured by blowing molten glass into a pear shape, about 60 to 75 cm long by 20 to 25 cm in diameter. The ends were removed and the resulting hot cylinder was split with shears and flattened on a sanded iron plate. Broad glass is textured and contains imperfections, picked up from the flattening process. The glass is thin, frequently with a grey tint. Due to the limitations of the cylinder size, panes of broad glass were very small, so they were fixed together by a lattice of lead kames to form small window lights, separated by timber or stone mullions.3 Crown glass, or spun glass, was the preferred choice for window glass from the late-17th until the mid-19th century. The glass quality was often very good, with an almost unmarked fire-finished surface. The crown glass making process was eloquently described by Henry Chance in 1888: A man… with a veil before his face, stands in front of a huge circle of flame, into which he thrusts his piece rapidly, meanwhile revolving his ponty (the iron rod). The action of heat and centrifugal To make crown glass, square panes were cut from a round crown, involving wastage. The numbers give the sizes in inches. Crown glass in production, from Roger Dodsworth’s Glass and Glass Making (1984) 1 George O’Brien (1918) The Economic History of Ireland in the 18th Century, Maunsel and Company, London. ² Andrew Carpenter, Rolf Loeber, Hugh Campbell, Livia Hurley, John Montague, Ellen Rowley (eds) (2015) Art and Architecture of Ireland Volume IV: architecture 1600– 2000, Royal Irish Academy. ³ Christopher Salmond (1995) ‘A Brief History of Glass’, Context 48, December. force combined is soon visible. The nose of the piece expands, the parts around can not resist the tendency… the next moment, before the eyes of the spectator, is whirling a thin transparent circular plate of glass which but a few minutes before was lying in the glass pot. The disc, ranging between 1.4 to 1.8 metres in diameter, was cut into orthogonal panes, with some resulting wastage. The central section of the disc, the bullion, was usually discarded. Crown glass is slightly concave and often has distinctive semi-circular lines. It is thinner, brighter and more reflective than cylinder glass.
16 CONTEXT 177 : SEPTEMBER 2023 Polished plate glass was manufactured from 1773, providing high quality glass, mostly for use in mirrors, coaches, shopfronts and the homes of the very wealthy. The process was very labour intensive and therefore expensive. Molten glass was cast on to large iron tables, rolled flat, and then placed in an annealing oven to cool. A grinding wheel was used to Manufacturing mechanical cylinders Creating mouthblown cylinders remove roughness and polish the glass to a very smooth finish. In 1789 the British Cast Plate Glass Company began using a steam-powered machine to grind and polish plate glass, a process permitting large panes. The glass was thick and heavy, to bear the large size, and glass tax made it expensive at the time. Improved cylinder glass became available in the early 19th century, following developments in the earlier broad sheet process. Blown cylinders were swung in a trench to achieve sizes of around 4 x 0.6 metres. Larger resulting cylinders were flattened out and cut into sizeable panes which were more affordable and of better quality than crown glass. Improved cylinder glass was used to glaze the Crystal Palace in 1851. Cylinder glass has a slightly rippled surface and long air bubbles align with the ripples to form straight, parallel lines. Machine drawn cylinder glass was produced from 1903, when glass manufacture was developed on an industrial scale in the USA, propelled by advances coal and gas firing technologies. The American Window Glass Company in Pittsburgh, Pennsylvania, developed a method for making very large cylinders 12 metres high. These were mechanically drawn vertically from a circular tank, after which the glass was slowly cooled, cut lengthways, reheated and flattened to form vast sheets of cylinder glass. In the UK machine drawn cylinder glass was manufactured by Pilkington from 1910 to 1933.
CONTEXT 177 : SEPTEMBER 2023 17 WORKING WITH GLASS Flat drawn sheet glass, emerging in Belgium in 1913, was produced in Kent in the UK from 1919. The glass was drawn vertically in a flat sheet until it cooled sufficiently to allow the glass to be cut. The glass has a wave in one direction only. Single and twin ground polished plate glass was cast and then ground and polished on a conveyor belt to a fine quality without distortion. Single ground was available from 1923 and in 1935 Pilkington developed the twin ground polished plate system. A continuous ribbon of glass about 300 metres long was ground simultaneously on both surfaces in the electrically powered machine, with enormous grinding wheels fed with progressively finer sand. Float glass, which is now ubiquitous, had emerged by 1960. Earlier glassmaking processes relied on interrupted sequences of firing, shaping and cooling of glass. In the 1950s Sir Alistair Pilkington invested large amounts into developing an interrupted process to continuously manufacture large quantities of glass. A continuous ribbon of molten glass was floated onto a bath of molten tin, held in a chemically controlled atmosphere at a high enough temperature for a long enough time for the irregularities to melt out. During the process, the surfaces of the glass became flat and parallel, assuming the dead flat qualities of the molten tin, and resulting in a reflective and unblemished glass.4 In 1959 Pilkington successfully produced high quality glass in this method, which is used to this day to produce window glass. Until recently, float glass was produced in different grades, with lowest grade ‘horticultural glass’ containing slight imperfections. It was used for greenhouses and industrial buildings, and as replacement for crown glass in conservation. Early double glazing As early as the 19th century, concerns about heat and noise transfer of windows led to developments in double glazing. In 1865, an American, Thomas Stetson, patented a simple system comprising two puttied sheets of glass with a narrow cavity and a timber spacer bar. The system had its limitations, as it did not allow for differential movement between the two glass panes. Double glazing was manufactured in the US on a commercial scale by 1944, but it did not take off in the UK until the 1970s.5 Double glazing was initially difficult to retrofit into historic windows because of the deeper glazing rebate required by the double glazing unit. Developments in ‘slimglaze’ technology in recent years have permitted slimmer glazing units to be fitted into older windows, resulting in the loss of historic glass. Conserving historic window glass While local authority consent is generally required to replace glass on protected structures and in conservation areas, the removal of historic glass in the remaining older housing stock is continuously contributing to the loss of character in the towns and cities in Ireland and in the UK. Where traditional glass is present in a window, it should be retained if possible. Replacement of panes due to small cracks in the corners of panes should be avoided unless there is evidence of water ingress. It may be possible to repair larger cracks in very valuable glass with epoxy applied by a specialist. Replacement glass should match the original as closely as possible and may require sustainably sourced salvaged glass.6 Flat drawn sheet glass being drawn vertically in the Fourcault Process (Image: An advertisement for Union des Verreries Mécaniques Belges, Univerbel, La Maison, 1955) ⁴ L.A.B. Pilkington (1969) ‘Review Lecture: The Float Glass Process’, Proceedings of the Royal Society of London, Royal Society, December 16. ⁵ https:// passivehouseplus.ie/ blogs/double-talka-brief-history-ofinsulated-glazing ⁶ Inform Guide: Maintaining Traditional Plain Glass and Glazing, Historic Environment Scotland (2007) Katia Papkovskaia, a conservation architect, is an associate of John McLaughlin Architects, Dublin. Rolling polished plate glass
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