Theory into Practice at Surveying Seminar

Our latest seminar at Hartlebury Castle in Worcestershire saw some 35 delegates – architects, conservators and practitioners from far and wide – tackle the issue of Surveying and Recording Historic Ironwork.  The seminar opened with Paul Ashmore’s potted history of the Bromsgrove Guild, with an opportunity to view some of the Guild portfolios as well as a large wrought iron hinge that the Museum curators kindly brought out of storage for us, which prompted much interesting discussion.

There followed presentations from John Wallis (Dorothea Restorations) on understanding specifications, David Gent (Atkins Global) on surveying wrought iron railway bridges and Peter Meehan with a case study from Harlaxton Manor.

After a hearty lunch delegates were divided into groups and sent out to survey some historic iron gates within the castle grounds and at nearby St James’ Church.  Armed with photographs and clip boards and facilitated by the speakers and NHIG team, delegates were able to practically apply what had been presented in the morning sessions. Thankfully the weather remained favourable and the afternoon provided an excellent opportunity for group learning – a fitting end to a thoroughly enjoyable day.

Examining a hinge from the Bromsgrove Guild archives

Delegates grapple with the NHIG magnetic gate puzzle conundrum!

Scroll down to read more about the presentations in detail …

Paul Ashmore

The Bromsgrove Guild was founded in 1898 by Walter Gilbert a former art master at the Bromsgrove School, in partnership with William Whitehouse and architects Butler and Crouch. The Guild was established on ‘art and crafts’ principles and influenced by the philosophies of John Ruskin and William Morris. They followed the philosophy of earlier Guilds in that individual craftsmen remained anonymous and groups would be responsible for a single project.
The Guild brought new opportunities to the dying Bromsgrove nail making industry which had been overtaken by mechanised processes. Gilbert secured the services of skilled craftsmen from the famous Coalbrookdale Company and travelled the globe securing commissions and craftsmen as he went. Guild members worked from their studios and workshops in Bromsgrove Birmingham and London and had agents worldwide. As the Guild developed they collaborated with other makers and designers, expanding beyond ironwork to wood carving, stained glass, plaster, lead and textiles. No surprise then that they secured the prestigious commissions of outfitting the Lusitania and Mauretania.

In 1905 Gilbert obtained   the commission for the Buckingham Palace gates as part of Sir Aston Webb’s remodelling project.  Louis Weintgartner a designer of Swiss origin was significant in the guild and is credited with the great lock and royal coat of arms on Buckingham Palace Gates. On completion of this work in 1908 the Guild was issued with a Royal warrant and appointed metal workers to H.M. King Edward V11 and more commissions followed

The Guild produced exceptional ironwork for nearly 70 years that was exported all around the world including the liver bird of the Royal Liver Assurance company and the gates to Lords Cricket ground, to mention a few.

In 1918 Gilbert left the guild to work for H.H. Martyn of Cheltenham and many of the guild craftsmen followed him, possibly due to artistic differences or financial weaknesses. Thereafter, lack of demand – probably during the world wars – brought about the demise of the Guild which finally closed in 1966.

John Wallis gave an interesting presentation about understanding specifications from a practitioner’s point of view. He outlined the position that client, main contractor and subcontractor hold and the emphasised the importance of clear communication to define exactly what the client wants in the specification making reference to standards, principals and performance. Significantly, he pointed out that the specification should concentrate on what the client wants, not how it should be done which should be established through a conversation with the practitioner directly. He also covered CDM regulations 2015 site specification, security, supervision and insurance etc.

John pointed out that pictures often communicate information more effectively than words. Good drawings can give not only site location and assembly instructions but with the use of 3D and enlargement can provide all the necessary detail. He also highlighted the importance of setting realistic time frames for labour intensive work, especially allowing for inevitable difficulties in acquiring historic materials.

He gave an example of some work carried out on some Grade II listed gates which were being repaired. They had been restored recently but when the paint was stripped back it was found that repairs methods had not incorporated the correct material or used appropriate processes and barely resembled the original. Paint covers a multitude of sins but monitoring of the work can eliminate such errors.  Hence the importance of recording at different stages using a digital camera, which is invaluable in giving the client/main contractor a clear picture of what is happening at each stage, although there is no substitute for visiting the work in progress if possible.

John concluded by underlining the functionality of good specification including payment methods and conservation plans which should include historic content, vulnerabilities, heritage value and conservation policy. The question was asked about how detailed an initial specification should be. John replied that an initial phone conversation keeping a broad specification was best with detail being added as the process developed. He stressed how long detailed specs may take to price and emphasised that they need to be given that time.

The presentation included examples from John’s experience at Dorothea Restorations and was well received, with conversation spilling over into a coffee break.

David Gent

David is responsible for surveying railway bridges which are either in commercial use or redundant and used as cycle or footpaths. Some have had to be modified to cope with the higher demands of modern transport systems. Cast iron bridges are unable to cope and have had to be replaced. Surveying is in the first instance to ensure the structure is safe and recommend any repairs. Bridges are not often painted due to the high cost.

Gaining accesses is often with ropes and tackle and the surveyor would be looking to assess the construction form, section sizes and the surrounding environment (old structures become home to a variety of wildlife). Any existing drawings are often so old that they may take significant time to interpret. However, old photographs can often give good information. There is a hidden critical element with some bridges where the structure may be assessed as in sound condition but where the surrounding elements have issues.

Initially any inspection on unused bridges would be visual, looking at the corrosion and whether there was any reduction in material thickness. Accurate measurements are made with callipers and chalk and wax are used to detect cracks while hollow structures are examined with an endoscope. Details are recorded and photographs taken from which drawings can be made. David showed a photograph of the failure of a typical railway bridge not of the iron work but of the supporting parapet. Of the 4000 bridges tested for similar defects 100 were found to have similar problems.

Normal everyday testing would include hardness testing, ultra sonic thickness gauges, acoustic emission testing for cracks, magnetic particle testing and portable electron microscope. Measurements have to be accurate as a 2mm loss of thickness could result in the structure being condemned.

Repair techniques present their own problems: welding is avoided on wrought iron as it can contaminate the original material, rivet replacement by bolts can be problematic because when over-tightened they case stress corrosion cracking and stainless steel tends to set up galvanic action.

The presentation was based on the surveying of Bennerley wrought iron Viaduct which is now disused and a home to all manner of wildlife (infra-red is also useful for identifying this). He showed video footage taken by drones and from the information they provided, drawings were created to an accuracy of 5mm which enabled them to estimate how many rivets were missing etc. The drone technology allowed the survey to be carried out significantly quicker and more efficiently than conventional rope and tackle methods.

Peter Meehan

Peter’s presentation was a case study on the surveying and conservation of the triple iron gateway at Harlaxton Manor in Grantham. He started with a history of the 19th century manor house originally dating back to 1340. The wrought iron gates set in stone predate the house so were probably moved from elsewhere.

Peter’s slides showed the poor condition of the gates, highlighting corrosion delamination and failed hinges etc. Before he would carry out a survey he would try to find out as much about the history as he could and he would take with him camera, notebook & pen, tape measure, telescopic ladder, magnet and compass.

He would normally allow 3hours for a survey depending on the size of the project. Photographs with the compass would show the orientation. He would record material and section sizes, construction methods and any interesting features like makers’ marks. He would also record on the photographs any rust jacking, loss of section, wastage and previous repairs.

He takes paint samples, recording and photographing where they had been taken from and keeps the samples in a plastic bag. Samples are then set in resin and polished back to expose the layers. On these particular gates the layers revealed lead white, carbon black and linseed oil. He also commented on how the rusting ironwork had lifted the stonework pillars and split the stone in another area.

He talked a little on the repair program which had exposed maker/rolling marks and a space in the overthrow which would have been for a family cartouche very popular on 18th century iron work. The paint system used was an epoxy base coat with an oil based top layer which although not recommended by manufacturers does have a significant life span. The gates were refitted into the restored masonry using resin and then capped with lead in the traditional manner.

There was a question about lead based paints. These can only be used on Grade I listed work and require the permission of Historic England and the environment agency. It is also very expensive.

NHIG would like to thank the seminar speakers for their presentations and support. Hartlebury Castle for allowing NHIG to host the surveying seminar and their staff who were so very helpful.

 

 

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