Sheet Metal

[Marcus Velius Avitus]

I am trying to research something as it is a subject near and dear to my heart. I am a blacksmith and I was interested in probing this forvm full of smart people to see if anyone can point me in the right direction.

In ancient Rome, what was the general process of forging sheet metal. Would they simply take iron ore and forge-weld multiple pieces into one large mass and forge it out to a relatively uniform thickness? I imagine that this would be done by hand. I have acutally done this myself on a small scale(making small pieces of sheet). It is extremely labor intensive. Did the Romans have a means of speeding up this process (like running it hot through sizing rollers or anything like this)?

Basically my question is this: Was all Roman sheet metal hand hammered into sheets? If so how uniform was it? It would proabably depend hevaily on the skill of the smith doing it. Additionally, would this have been a specialized skill and were there manufactories that did only this(perhaps utilizing slave labor)

[jvrjenivs]

First, I don't think there is any general answer to be given. I have the impression that from several places that are identified as 'workshops', we can conclude (some) Roman craftsman knew what they were doing. Metals are found sorted out quite good for different qualities, and unfinished pieces are also found, which suggest that several craftsman had their own 'speciality' like making plate steel???

Anyway, to get more into your question, I would like to answer that with one example. (or a set of some archeological finds, actually). I've no idea however, how these reflect other specimens, as they are ornate and very crafted pieces. Now, it's all about the Nijmegen facemasks, of which you can see the original and a repro I got made here:



Lets concentrate on the masks. Nevertheless it's good to point out that several helmets like this were found in the area, and that most of them share the following feature. The mask was namely made out of layered metal. Folded 3 times, it thus was made out of 8 layers. I would say a craftsman thus had to hammer that piece out 4 times. Then the layer seems to be quite uniform, as (for what we can tell now) most of these masks were pretty uniform in thickness. (Not to mention that in this particular example (and 2 others) the iron mask was then covered in a second mask made out of silver sheet, glued to it At least the people working on these pieces knew what they were doing.

[mcbishop]

Basically my question is this: Was all Roman sheet metal hand hammered into sheets? If so how uniform was it? It would proabably depend hevaily on the skill of the smith doing it. Additionally, would this have been a specialized skill and were there manufactories that did only this(perhaps utilizing slave labor)

You need to see David Sim and Jaime Kaminski's forthcoming book Roman Imperial Armour (to be published by Oxbow) - he has metallographically analysed Roman armour, including plate armour, and concluded that it originates in a liquid state (the slag inclusions are apparently the big giveaway) and goes through a process - probably rolling - that ensures it is of a uniform thickness. The plates of bog-standard lorica segmentata are of a higher quality than the best Renaissance armour. David is a blacksmith so knows what he sees (and tests his reconstructions at Shrivenham). The paradox of Roman plate armour is that the plate is of high quality, but is put together by those whose skills left something to be desired in the handicraft department, so most lorica seg looks shoddy, to say the least.

Mike Bishop

[Matthew Amt]

Zoiks! Well, we're looking forward to that book, that's for sure! It might also be considered that a lot of items, especially non-Roman, were not necessarily started from sheet, as we would naturally do today. A helmet could have been formed directly from a plate or billet, without the bother of making it flat first and then making it not flat!

And we should add that sheet metal of alarming regularity was a pretty common item from as far back as the Bronze Age, all hammered out very laboriously. While iron can be forge-welded from pieces or layers (and is regularly folded to help remove slag), bronze sheet must be worked out from a single cast plate without significant flaws, cracks, or charcoal inclusions. And it is generally worked cold with repeated heatings to anneal it.

Those guys were good...

Matthew

[PhilusEstilius]

I do believe there are papers on the subject of smelting iron in the true Roman fashion by the late John Ansty who did a lot of this kind of work.

[Marcus Velius Avitus]

This is all good information. Thank you to all who replied! It is a topic that has always interested me(for obvious reasons). I had heard that the quality of Roman metal manufacturing was quite good and their knowledge of metallurgy was pretty sophisticated(without actually understanding chemistry, that is). It makes sense I suppose that even if the quality of the metals were good and well made - you must rely on the laborers in armor manufactories and shops to cut and assemble things. I look forward to such a book as was mentioned eariler!

[Medicus matt]

Zoiks! Well, we're looking forward to that book, that's for sure!

Out in June and available for pre-order at Oxbow at a bargain price.

Just wondering...I know that water powered trip hammers were used to crush ore on a large scale (I've sat on one of the anvil stones at Dolaucothi) but is there any evidence that they might have used the same principle to produce sheet metal from blooms or billet?

[Rutilia]

Pre-ordered that one, sure enough. I will be working my forge a fair bit this year. This helps. Excellent question too..and a grand link to go with it.

Those guys were *really* good.

Rutilia