Conservation of Architectural Ironwork

Conservation of Architectural Ironwork, David S Mitchell, Routledge, 261 page, black and white illustrations with some colour plates, hardback.

The last 20 years has seen a renewed appreciation of architectural ironwork, particularly that of the Victorian period. This has been partly driven by funding programmes such as the Heritage Lottery Fund’s Parks for People programme. Investment in urban parks which contain many fine iron structures, from bandstands to glass-houses, fountains to gates, has been significant. It is in this context that David Mitchell has produced his timely publication ‘Conservation of Architectural Ironwork’.

Starting with a history of iron, its manufacture and use architecturally, the book then describes the varied types, their chemical and physical properties, their weaknesses and decay mechanisms. It dispels many oft-perpetuated myths regarding iron (cast and wrought) and steels. Mitchell effectively combines technical and scientific information with practical descriptions and a clear narrative history.

The book covers the diverse and ever-evolving manufacturing processes and the development of alloyed materials, through to common weaknesses and even manufacturers’ tricks to conceal defects in poor-quality castings. The most infamous example is the use of Beaumont’s Egg (a composition of beeswax, fiddler’s rosin, iron borings and lamp-black) in the casting and manufacture of the Tay Bridge near Dundee, which consequently collapsed in 1879. An excellent overview of the survey of iron structures provides practical advice on the application of a variety of survey techniques to identify different materials and make diagnostic assessment of defects. It highlights the potential pitfalls and illustrates how easy it is to make erroneous assumptions.

Unusually for a technical conservation publication, the robust management of a project and its material effect on the outcome are given a significant weighting. This is both refreshing and helpful. The conservation practitioner, in any field, would do well to read the sensible processes outlined. The book acknowledges the reality of working in a procurement-led, cost-driven environment, and provides a sound methodology to achieve good conservation outcomes.

Mitchell addresses the philosophical and technical challenges faced when conserving an iron structure. From the removal (or not) of surface finishes to wide-ranging corrosion issues, the principles of repair and the inherent challenges of different types of iron are covered in detail and cross-referenced to practical examples. As with most conservation work, there is rarely a definitive right answer, but Mitchell paints a clear picture and establishes a robust framework within which to make decisions.

The narrative on fixings and their appropriateness is particularly interesting, balancing the technical, philosophical and aesthetic rationale for using traditional or modern fixings in particular contexts and environments. The illustration of the factors to be considered when joining different metals and the consequent potential specifications are invaluable. Following a discussion on the relative merits or weaknesses of different coating systems, traditional and modern, Mitchell effectively illustrates the themes of the previous chapters with a series of detailed case studies.

Throughout the book the descriptive text is supported by well-considered and appropriate examples and illustrations. It is entirely appropriate that the book uses Scottish examples extensively (Mitchell is director of conservation at Historic Environment Scotland) as the great Scottish manufacturers were leaders both in the global market place and in technological innovation.

A well-thumbed copy of ‘Conservation of Architectural Ironwork’ should be found on the shelves of all conservation practitioners. The philosophically robust, yet practical approach not only provides a sound framework for the conservation of iron structures, it has a much wider potential application as a benchmark for developing approaches to the conservation of modern component-based buildings.

This article originally appeared as ‘Hard lessons’ in IHBC's Context 157 (Page 61), published in November 2018. It was written by Robert Chambers, director of Chambers Conservation, Chester.

--Institute of Historic Building Conservation

Related articles on Designing Buildings Wiki

• Cast iron.
• Code of Practice for Ironwork Systems Installation and Refurbishment.
• Conservation.
• Difference between cast iron and wrought iron.
• Failure of cast iron beams.
• IHBC articles.
• Iron.
• Ironwork.
• Steel.
• The Institute of Historic Building Conservation.
• Wrought iron.