A breastplate shown with its x-ray and sectional view demonstrating its bullet-proofing.

Duplex bulletproof armour

The question

During the 16th-century improvements in firearms and gunpowder led to the wearing of fewer, but thicker pieces of armour. In recent years it was realised that some of the surviving breastplates had been made by combining two thinner plates. X-radiography was undertaken to identify maker’s stamp marks on the rear plates or those that are obscured by paint or corrosion on the front.

Results of analysis

X-radiography very successfully allowed many maker’s marks to be identified so that the date and provenance of the breastplates could be determined. However, the X-radiographs also revealed an entirely unexpected feature. Some of the “duplex” armour contained three breastplates. Others had further scrap iron or even armour, such as a tasset from a pikeman’s leg armour, sandwiched between the inner and outer plates.


In an additional twist it appeared that some duplex armour was not simply cobbled together old armour, but had been newly made that way. Was this to provide more effective protection? A clue to the possible benefits of such armour may be found in 19th-century research into the protection of iron-clad ships. Penetration by the projectile is achieved through the propagation and growth of a crack in the metal. Where two layers are used the interface between the two acts as a barrier to the crack and thereby prevents failure.


Since publication in the Arms and Armour Journal, many more examples of duplex armours have come to light worldwide. It is hoped that recent collaboration with the Technical University of Delft into the impact resistance of armour will be expanded to test the relative merits of single and double layers of armour.

Did you know?

Too hot to handle

Before the Smith & Wesson .44 Magnum revolver, the most powerful handgun in the world was the Mars pistol. It was so powerful that, during testing in 1906, the Royal Navy vowed never to fire it again.