A series of 4 metal samples as see under a microscope.

The metallurgy of plate armour

The question

Traditionally, the development of armour is explained in terms of stylistic changes. Are there also changes in the availability, use and working of different ferrous alloys that would contribute to the effectiveness of these armours against increasingly more powerful projectile weapons?

Results of analysis

Medieval armour is now one of the best-studied areas of medieval metalworking. The picture that has emerged shows trends in both the choice of materials and their working. For example, for the famous south German armourers, until the end of the 15th-century most armour was of unhardenable iron. However from around 1500 there is a transition to steel and this was carefully heat-treated to harden it.

The Greenwich workshops founded by Henry VIII appear to have used materials from the same sources but seem to have been slower to fully harden their steel. However, cheaper munition armour was always of iron or sometimes an alloy of iron containing a small amount of phosphorus, which gave a marginal increase in hardness.


Metallographic studies have shown that at a time when efficient firearms were making their appearance on the battlefield, the high quality armour centres sought the best quality materials and developed metallurgical techniques to ensure that the wearer of their armour remained well protected. Such expense was, however not extended to the armour of the ordinary soldier on the battlefield.


Much of this research reported above was carried out as part of the Royal Armouries’ Science Officer’s PhD research. However, the specialist who has worked most extensively on European armour, including much from the Armouries Collection is Dr. Alan Williams who has published widely including a recent major volume entitled the Knight and The Blast Furnace (Brill, 2003).

Did you know?

4 Eiffel Towers

During the siege of Sebastopol the British fired about 10,000 tonnes of iron shot; the French fired 510,000 round shot, 236,000 howitzer shells and 350,000 mortar shells – a total of around 43,000 tonnes of iron! About the same weight as 4 Eiffel Towers.