Making Roman Republican helmets

[Erpingham]

I was watching Larry Lamb's series on the rise if Rome on Channel 5 on Friday and it contained some interesting bits and pieces on the Punic Wars.  One was a discussion of helmet making.  It was suggested that the Romans originally cast their bronze helmets but, with the expansion of their army, took to mass producing them by spinning them up on animal or slave powered lathes.  There was no mention of raising helmets from sheet bronze.  Perhaps significantly, the demonstration of helmet making was done on a modern powered lathe, not on any reconstructed Roman equipment.  I admit to being a bit sceptical, so is anyone aware of this mass production technique?

[Patrick Waterson]

It seems to be taken for granted by re-enactors Legio XX that late Republican and early Imperial helmets were spun.

One should note this applied only to bronze helmets because iron was too hard for this technique.   Also, the examples of historical helmet finds listed as having spin marks are all coolus helmets (see the first picture on this page) and I am not sure which other types the technique may have been applied to.

It does however seem to be solidly attested by the mute markings in the brazen helmet-bowls.

[Duncan Head]

Spinning seems fine - Russell Robinson was already talking about spin marks in the 1970s. But casting may be dubious:

It has often been said that some ancient helmets may have been cast, including some Montefortino forms. This has never been satisfactorily repudiated. Firstly, casting would make the bowl very brittle due to the change that the crystaline structure undergoes especially when the walls of the helmet bowl are usually 1.5 mm thick. Furthermore without a modern vacuum chamber it is unlikely that the bronze could be forced to fill all the cavities in the mould. The work involved in preparing an original and then preparing a mould and finally casting the item, would far outweigh the cost of it being raised by beating. It has also been suggested that the basic form of the helmet was cast and then the bowl was reannealed and worked but this would not sufficiently alter the cast structure of such thin bronze so as to overcome the brittleness of the cast metal. These assertions are confirmed by Craddock (1984) whose recent analyses of Etruscan helmets in the collections of the British Museum indicate that all the helmets tested had been raised from sheet metal and not cast.

- from John Miles Paddock's thesis The Bronze Italian Helmet: The development of the Cassis from the last quarter of the sixth century B. C. to the third quarter of the first century A. D. available from http://discovery.ucl.ac.uk/1348999/

Paddock does accept that some helmets had separate cast decoration attached, including Montefortinos with cast crest-knobs, which might partly account for the idea that some helmets were cast. He reckons spinning was widely adopted in the 1st century BC, on Montefortino helmets, when the scale of production became so great that the advantages of lathe-spinning offset the setup costs (producing the lathes, etc).