The Wallace Collection in London is a national museum that includes the largest collection of arms and armour in London. The collection has a conservation department that has been analysing Medieval armour for the last 20 years by using metallography. This is the microscopic examination of a prepared edge of a plate from a suit of armour.
This is an non-invasive technique, since a sample need not be detached. However, it is not suitable for swords , nor for objects which do not have a rim where the plate was previously cut. To examine swords from the Oriental Armoury, or difficult helmets, such as that belonging to the Black Prince, in Canterbury Cathedral, the conservation department investigated the feasibility of using alternative, non-invasive, techniques to study these historical artefacts. One of these was neutron diffraction, which causes no damage to the sample.
The technique of neutron diffraction works by the neutrons passing through the sample material and interacting with the the atoms. Different crystalline phases interact with the neutrons differently, allowing them to be detected separately, and so the steel may be analysed.
The helmet of the Black Prince hangs over his tomb in Canterbury cathedral. The Black Prince, Edward of Woodstock, was born in 1330, eldest son of King Edward III. He was only the second holder of the title of Prince of Wales, victorious against the Kings of France at the battles of Crecy and Poitiers, but who died in 1376 before succeeding to the throne.
The shape of the helmet made analysis difficult by metallography, so it was brought to the ISIS Neutron and Muon source to be analysed using the INES instrument.
Curators had wondered whether it had been a working helmet worn in battle, or simply a piece manufactured for decorative purposes after the funeral.
Neutron diffraction showed evidence of microstrain in the metal in the (2mm thick) front plate. This was evidenty due to the helmet receiving a blow which dented it and was later repaired by hammering, without annealing, leaving no visual damage but hidden microstrain.
As well as this helmet, numerous artefacts from the the Oriental Armoury of the Wallace collection have been brought to ISIS for analysis. Many of these were made of crucible steel.
Crucible steel is a type of steel prepared in a unique method developed in the middle east. The steel is made by placing lumps of iron with lumps of carbon rich plant material in a covered crucible and heating them up over a long period of several hours, or even days, to form an ingot of high-carbon cast steel.
Damascus steel or wootz is a name for patterned crucible steel. Damascus steel swords are some of the most famous in history. Made in India and Iran they had a very high carbon content, and also had a ‘watered-silk’ or ‘damask’ pattern on their surface, which was regarded as evidence of the quality of the steel, and justified their considerable cost.
Tabarzin are Indo-Persian saddle axes carried by horsemen. They frequently exhibit patterns on their surfaces which appear to be Damascus steel. However, over time, poor maintenance and corrosion has led to the pattern being obscured.
In order to view their original patterns, 16 Indo-Persian axes were brought to ISIS for analysis using neutron diffraction. This technique allows the measurement of the relative concentration of ferrite and cementite and, from that, the carbon content of the steel can be obtained. In addition, if any anisotropy in the distribution of cementite can be found then the presence of a surface pattern, even if hidden, can be deduced.
Each axe was measured in several areas, and it was found that very few of the sixteen axes brought for analysis were made up from steel of any significant carbon content. Many were simply just iron, with only one of the sixteen being made from crucible steel. However, it appeared as though there were three axes that were actually veneered with a thin layer of high-carbon steel over the top of the iron, in order to create the illusion of the axe having been made from Damascus steel. These were evidently made as contemporary fakes, due to the high cost of making genuine Damascus steel.
One unique piece in the Wallace Collection is a jewel studded dagger which had belonged to the Mughal Emperor, Shah Jahan (builder of the Taj Mahal).
When examined using the INES beamline at ISIS it was found that the carbon content of different areas on the sword confirmed it was a high carbon crucible steel sword, consistent with that of the finest Indian and Iranian blades, so it had been made from what was then the best steel in the world, for the richest man in the world.
These findings were all published within the book ‘Arms and Armour: Essays in honour of David Edge.’ David Edge was the head conservator of the Wallace Collection retiring in 2020 after an incredible 45 years working at the collection. The work carried out by the Wallace collection in collaboration with ISIS won the 2018 ISIS Society Impact award for the utilisation of neutrons for non-invasive analysis of arms and armour. The neutron analysis undertaken on these historical artefacts has offered an eye-opening insight to the fascinating history held within the pieces of arms and armour that would not otherwise be obtainable.