When David Starley, an archaeometallurgist-inspired artist, wanted to restore and conserve a 12th century stained glass window at Canterbury Cathedral he turned to materials science. Here we get an insight into how one company turned its demo centre into a testing centre for ancient materials
When looking for suitable laboratory facilities for his metallography studies, archaeometallurgist David Starley, was recommended by fellow ancient metallurgist Dr Ellie Blakelock to contact Spectrographic, supplier of metallographic equipment to the material science industry. The company had recently set up a new preparation centre for product development and customer demonstrations – an ideal space for David to carry out some of his more complex work.
David, whose background includes working as a metallurgist for the former English Heritage Ancient Monuments Laboratory and The Royal Armouries, is a specialist in archaeometallurgy with 25 years’ experience. He currently provides freelance metallurgical services to archaeological units, museums and other heritage organisations. He has worked on many projects of historical importance, including the study of Roman metalworking debris from North Yorkshire and Saxon weapons from Essex.
Recently David’s work has involved him in the restoration and conservation of the 12th century stained glass window at Canterbury Cathedral in Kent. Canterbury Cathedral is one of the oldest Christian structures in England, having originally been founded in 597.
The project required David to examine samples from the ferrimenta – the ironwork supporting the stained glass panels. The medieval window supports are made from traditional bloomery iron, which are estimated to have been smelted in a furnace around 1190. It was this particular project that led David to get in touch with Spectrographic.
Paul Chippendale, Managing Director at Spectrographic was intrigued by the request, and offered his facilities to David, keen to support a project of such historical importance. Though only a minority of David’s work requires metallography, it is this aspect that he finds the most difficult to facilitate. Access to good laboratory facilities – that are well maintained – is unusual. Paul was delighted to support David’s work, which he recognised as being of historical importance and valuable for preserving the heritage of this country.
As a supplier of metallographic equipment and consumables to the material science industry, Spectrographic offers a range of metallographic products and equipment for material science analysis and quality inspection procedures, as well as advice in material sample preparation, computer based image analysis and microscopic inspection. Based in Baildon, West Yorkshire, the company was set up, and continues to be run, by Paul who is a skilled metallographer with over 20 years’ experience. They work regularly works with expert metallurgists working in the automotive, oil and gas and aerospace industries, and for higher and further education establishments.
Using metallography to study historic buildings is quite a rarity - and, due to the nature of the material he was working with, David wanted to avoid simply handing the precious samples over to a person familiar only with current day alloys and metals. He needed to be in a position where he could examine the samples himself, and Spectrographic’s demonstration centre provided the perfect solution.
Working with Spectrographic and with the Royal Armouries in Leeds, David was able to access the specialist equipment necessary to study the extremely rare and precious ferrous samples taken from the ancient ironwork supporting the stained glass window panels. Once the samples from Canterbury Cathedral’s iron window frames had been polished and etched, David could begin his evaluation.
The metallographic examination of samples from the ferrimenta, an impressive one tonne iron structure, showed the remarkably low slag content of the metal – far less than is encountered in wrought iron of a more recent date. Combined with a purity obtained by the relatively low smelting temperatures of the medieval bloomery furnace, and the use of charcoal fuel, this may largely explain the remarkably good condition of the ironwork, which did not show the laminating corrosion normally associated with wrought iron exposed to the British climate.
A feature of the window is the external grille of metal which served, like a modern space frame, to provide stability for large ecclesiastical windows prior to the introduction of stone tracery. The South Oculus at Canterbury is the last surviving example of this construction and the metallographic study provided evidence of its contemporaneity with the ferrimenta.
The ironwork of the window had not survived 800 years unscathed. An old repair had been made prior to the introduction of bulk steel. More recent damage was thought, on the basis of Neumann banding, which occurs under extreme stress conditions, to date to 1942 when the cathedral suffered damage during the second phase of the Luftwaffe's Baedeker raids. It was testament to the strength of the structure that although the shrapnel had completely removed a section of the ferrimenta, the integrity of the frame survived.
It is no coincidence that David lives and works in Saltaire – a 19th century industrial village recognised by UNESCO as a World Heritage Centre. Saltaire was the masterplan of the Victorian industrialist and philanthropist Sir Titus Salt, who instigated the village’s ambitious urban plan and high architectural standards. David is an artist in his own right, and has recently opened a gallery in the village, where his work is on display.
David’s art is usually inspired by the natural and historic landscape of where he lives, and includes both Yorkshire landscapes and street scenes. However, some of his recent, experimental, works relate to the metallographic structures he so often captures under the microscope.
David has also been instrumental in the promotion of the Saltaire Living Advent Calendar community event – which sees a series of 24 decorated windows lit up around the village each December. His living advent calendar design for 2012 (in David’s own words) “forms a conventional snow scene, the elements are all inspired by the crystal structures of metals and metalworking debris viewed down the microscope.
“The ‘fir trees’ are dendrites, which form when molten alloys solidify against a cooler surface. In the foreground a crystal structure likened to ‘straw on snow’ is typical of quenched steel, whilst the hills are partly transformed mineral ores. The sky is a black glassy smelting slag matrix from which small angular crystals of magnetite have precipitated and a single droplet of iron provides a full moon.”
And it is perhaps David’s affinity with art that makes his work at Canterbury Cathedral all the more significant. Early metalworkers were often remarkable craftsmen whose skill and understanding of their materials deserves our admiration in the industrial age. At Canterbury Cathedral, the most important pilgrimage destination in medieval England, innovative metallurgical technology was linked with art and religious devotion to create a structure worthy of the centre of Christianity in England.
Meanwhile Spectrographic’s demonstration centre – located only a short distance from David’s studio in Saltaire – has morphed into a testing centre for ancient and precious materials. Displayed in prime position on the walls above the high specification cut mount polish tools, high performance microscope cameras, and research grade metallurgical microscopes for the analysis of microstructures, is one of David’s dendritic-inspired artworks.
[caption id="attachment_33720" align="aligncenter" width="300" caption="Archaeometallurgist David Starley studies precious ferrous samples at Spectrographic’s preparation facility in Baildon, West Yorkshire. The monochrome artwork displayed, was produced by Starley for Saltaire’s Living Advent Calendar 2012, and was inspired by the metallographic structures viewed only under the microscope."][/caption]
01274 966 173
Further information about David Starley’s archaeometallurgy work can be found here. Details about his Saltaire gallery are available at http://davidstarleyartist.davidstarley.com/