Metal thickness in helmets

[Urselius]

I wondered if anyone had studied the relative average thickness of metal in the major skull elements of ridge helmets in comparison to the earlier helmet types with the skull and neck-guard raised in one piece.

It struck me that it would be easier to make the separate elements of a ridge or spangenhelm helmet thicker, and therfore more robust, than the single large piece of iron of the earlier types. This would be a possible reason for their adoption.

[Peroni]

Makes perfect sense.

[Ironhand]

Plus a point Matt Amt just made on a recent post, it is very easy to ruin a helm when dishing a one piece. As a smith if you spent many good hours smelting iron it is probably much safer to make a smaller piece. The image of the lone smith beating iron in his forge is usually a false one as few smiths would have at least an apprentice . By making the helm in pieces it allows several people to work on it at one time as well. You do not sacrifice quality, but get the work done more expediently. Perhaps it also helps the smith focus on his work more. If he takes his time he can use his best ore on the helm and make sure each piece comes out perfectly. Probably while also working on other projects and not having to focus exclusively on making the helm. You could forge a piece here, a piece there, use some of the lesser quality ore you smelted to make a sax to sell in the meantime and before you know it you have a helm done and have devoted your full attention to each piece without feeling rushed.

[Gaius Julius Caesar]

Hmmmmm, still, the quality of the one pieces would have required great skill, just look at the corinthian....

[Ironhand]

You're right without question Gaius, but it seems that there is often a trend in thinking that one piece helms are all extremely well made pieces while spangens are poorly made. It doesn't have to be that way at all. A one piece helm can be made out of poor material and hammered out quickly and a spangenhelm can be a superior quality piece of work. It all comes down to the smith.

[richsc]

when dishing a one piece

Actually, I got that break when sinking the metal. Dishing, where I would have done a bowl first, doesn't stretch the metal the same way at all, and with raising you're pushing the metal to the outside as you reduce its size, so it gets thicker at the edge.

Sinking may work if you start with a lot of metal in the center and thin it as you go, but you can't order that sort of thing. I imagine you could work with a really thick gauge and hopefully end up with enough metal at the center when you're done. Then you would also end up with edges thicker than the center, as Matt observed. But I think raising is a lot more predictable as if it is wobbly at the edge you can always straighten that out, but a tear in the center is a complete loss. (unless someone has a suggestion for fixing it??)

[Matthew Amt]

Uh, terminology problem here--I thought "dishing" meant the same as "sinking"! Hammering the metal into a depression. The metal thins in the middle. In raising, hammering the metal from the outside, the middle stays pretty much the same while the edge thickens.

Right, starting with thicker metal is the obvious solution. But as Richard points out, the ancients didn't necessarily start from flat sheet. They'd work down a billet, and could start dishing without progressing to a large flat piece. So they could keep the metal thicker where they needed it.

Matthew

[Dean Cunningham metalsmim]

here is a monkey wrench. You can raise from the inside so you can sink and raise if you want to shorten the hammer time. You shrink or raise in the wrinkles that happen naturally on the edge of the piece you are dishing or shinking. It is becoming more and more obvious to me that most ancinent smiths worked from the out side mostly, meaning most things were raised rather than dished.



Generally mating pieces is not the easiest thing in the world to do but the overall skill level needed is greater for raising. Making a spangenhelm would indeed give the smith an easier time of construction and allow him to make certain pieces thicker. But making some part of the helmet thicker might be a moot point when when you over lap plates.

[Urselius]

I imagine that heating the metal for half a helmet bowl evenly would be easier than trying to heat the larger piece of metal for a combined one-piece bowl and neck guard evenly. Would this tend to make producing a helmet with even metallurgical characteristics (quenching for hardness etc) easier if it were a composite of smaller pieces?

That is, would a composite helmet composed of individually better metallurgically optimised components be inherently tougher, less liable to contain internal flaws, than a helmet raised in one piece - given contemporary technological constraints?

[afmayer]

Why wouldn't roman fabricators cast the helmets first, then finish them by smithing? I read in the October/November issue of Ancient Warfare, "Sturdy Casques of Bronze: Five Hlemts in the Glasgow Museum", that "... analysis of early Montefortino helmets, including some from the former Axel Guttmann collection, has demonstrated that they were initially cast then overworked by hammering."

This is in reference to bronze, but why wouldn't it continue for iron? It makes perfect sense and saves so much work and keeps the metal thickness even throughout the helmet. Casting alone? NO! Cast then toughen-up with hammering? Why not?

Andy Mayer

[LUCIUS ALFENUS AVITIANUS]

Cast iron it's dificult, because needs a lot of heat and the iron dont smelt so liquid as copperallloys, silver or gold. You can cast a billet, but (in roman times) it's veruy difficult to cast a complex shape.

[Matthew Amt]

Generally speaking, the Romans didn't have cast iron. (There is only one *possible* exception that I've heard of.) Cast iron did occur now and then, but iron picks up so much carbon when it melts that it is far too hard and brittle to work. So it was considered a waste product until around the 17th century. Roman iron production did not actually melt the iron to get it out of the ore, so it was never in liquid state. If you do succeed in casting an iron helmet or helmet blank, it will be both far too thick to use, and far too hard and brittle to work with Roman forging technology.

The whole concept of cast bronze (or brass) helmets still leaves me dubious. They're just too thin! The folks I know of who do bronze casting are pretty sure that it is nearly impossible to cast an item that large less than 2mm thick. And since most helmets are less than 1mm thick in many places, I just don't see it happening. Even a 2mm thick helmet is going to weigh 7 or 8 pounds, at least, and I've never seen an original that weighs more than 4 (usually less than that!) Now, it is quite possible that a flatter or partly-domed blank was cast, and then hammered out to the desired form. This would explain casting voids still detectable by Xray, if they're in the rim or maybe the crest knob. Problem is, I've never heard of any molds or pieces of molds like that, though I've seen molds of many other items. We've also never found any partly-finished cast helmet blanks (from ANY era!), though there are a couple surviving Roman helmets which are clearly unfinished but clearly not cast (plus other unfinished cast items).

Even if casting a whole bronze or brass helmet were possible, there would be MANY unsuccessful casts for each success. Any holes or cracks in a bronze or brass helmet can only be repaired by riveting on a patch, which is practically never seen on surviving originals. (Whereas on a hammered iron helmet, you can forge-weld on a patch which may be good enough to be detectable only by Xray!) When you consider how many days go into the production of a mold for a single item, then consider how low the chance for success is for something that complex, it just doesn't make sense any more. Casting can go wrong at any number of places in the process. But hammering a thin plate or sheet into a helmet is basically only a day's work, with far less potential for complete failure of the process.

Even so, I'd still like to see more details of the analysis done on those bronze helmets that were supposedly cast and then worked. It's important information, and a brief summary doesn't tell me enough!

Valete,

Matthew

[Tarbicus]

But cast copper cheek pieces have been verified by the British Museum as genuine, attached to the helmet (a Weisenau IIRC).

[Endre Fodstad]

It would be far easier to cast a set of cheek pieces than a whole helmet, Tarbicus. Copper or copper-alloy, by the way?

Roman iron production did not actually melt the iron to get it out of the ore, so it was never in liquid state.

I believe that's only partly correct, Matthew. In a bloomery, some of the iron will exist in a molten to semi-molten state. This is not desireable, as you have noted; the pig iron produced melts out into the slag tap in the bloomery. Some "cast iron" will appear in most reconstructed bloomery ironmaking experiments; it would typically be recycled if possible by bloomery operators in ancient and medieval times, if possible.

Pig iron was produced intentionally before the 17th century in Europe; from the 12th century onward (the newer datings of the complex in Norberg are from around 1150, meaning Tylecote's hypothethised mongol connection isn't applicable. I have read some references to a german language article said to claim central european blast furnace finds from before 1100, but haven't tracked it down yet), swedish blast furnaces produced pig iron for decarburization into wrought iron and export - this process spread (or was separately invented) to germany in the 13th century. However, cast iron artifacts - appear much later; mid-to-late 14th century at the earliest.

[Tarbicus]

Copper or copper-alloy, by the way?

Copper, not brass or bronze.