Pompeii fixed potholes with molten iron (2019)

I am sceptical on how they figured out iron stains are pothole fillings. I think much simpler explanation would be everyday items or metal pieces of carts getting stuck between stones.

jl62• 2 years ago

I do find this quite hard to believe. Iron would be considered an expensive material to use in roadbuilding even today. The pictures aren't all that convincing.

But lead author Eric Poehler of the University of Massachusetts Amherst writes that stray iron drops found on the street suggest that the molten metal was carried from a furnace to the repair site.

If the hypothesis is that they were capable of carrying molten metal from a furnace to the road, isn't it more likely that these are splashes or spills from molten iron en route to a blacksmith?

yard20102• 2 years ago

You say "even", as if the Roman empire wasn't on par with the western empire today. I disagree. Even though we're at the tip of the ice berg, the human history is episodic in a way.

sushisource• 2 years ago

as if the Roman empire wasn't on par with the western empire today

Huh? I mean, no, technologically it... definitely wasn't. Remind me how many teraflops the most powerful Roman computer was capable of?

The Romans were plenty advanced, sure, but that's just a nonsense statement.

adriand• 2 years ago

I'm currently reading a book about Cleopatra [1] (it's superb) and I've been absolutely boggled by the productive capacity of the nation states of her era. Whether it was building ships, growing and transporting grain or raising armies, these were highly sophisticated bureaucracies that knew how to make, grow and transport huge quantities of stuff.

I'm at work and don't have the book on me, so I may have this slightly wrong, but IIRC, in Cleopatra's day Alexandria (where she resided with her court) was consuming 300 tons of grain per day, which arrived on ships via the Nile. Or consider the ability of Rome to draft and train legions of highly-skilled soldiers: it was at a scale similar to that of modern-day Russia.

1: https://www.goodreads.com/book/show/7968243-cleopatra

lukan6• 2 years ago

I am somewhat sceptical, as iron was very expensive back then. And they do not come up with a working idea how they possibly could have done it in an economic way. Portable smelters were not really a thing. And building an oven next to every hole does not sound too practical either. At least not easier, than just fixing the holes with stones.

Also shouldn't we have found other instances, where it was done?

"The researchers found that repairs using liquefied ore were being carried out just before the city’s destruction."

So my first (uneducated) guess would rather be, that hot lava might have tampered with the evidence.

jl62• 2 years ago

I also thought "hang on a minute. Pompeii? As in volcano Pompeii?" but apparently the city was never flooded with lava, but rather ash, which was cooler than would melt iron (still fatally hot though).

lukan6• 2 years ago

The eruption was a violent explosion with molten rocks flying around. Some of them probably hit the city and some of them contained lots of iron would be my guess.

littlestymaar• 2 years ago

Even with Lava, you're not going to melt iron, even when' it's just leaving the volcano it's not generally hot enough, and by the time it reaches the city it's even colder.

The melting point of iron is very high, and that's why for a long time iron was never molten even during the production process (slag was, but not the iron)

0cf8612b2e1e• 2 years ago

Also from the Wikipedia, I learned that people died of the heat and not suffocation. Which means that episode of Stargate lied to me where they claimed the opposite.

  A multidisciplinary volcanological and bio-anthropological study[53] of the eruption products and victims, merged with numerical simulations and experiments, indicates that at Pompeii and surrounding towns heat was the main cause of death of people, previously believed to have died by ash suffocation.

yard20102• 2 years ago

Apparently, using ships ballast was a common practice throughout the last 500 years. You have to have it on the ship anyway.

swatcoder• 2 years ago

And they do not come up with a working idea how they possibly could have done it in an economic way.

... are you sure about that? I haven't pulled the paper, but the abstract suggests that doing exactly that was central to the research.

https://www.ajaonline.org/article/3863

lukan6• 2 years ago

I probably should get the actual paper, yes. The articles are not that great, one has to read between the lines, that they talk about iron ore and not pure iron. Or rather iron slag. The byproduct of melting.

But I meant the economics of getting the liquid iron (or slag) to the holes. If there were many furnaces nearby, maybe they just used that and carried it some meters, but longer distances?

ricree• 2 years ago

Unless I'm mistaken, this strikes me as a really incredible claim. To the best of my knowledge, Rome didn't make much use out of cast iron. Iron has a very high melting point, it's not something that people were just casually melting. There were a few exceptions, but my understanding is that Europe mostly didn't use cast iron until late in the middle ages.

The idea that some random resort town was casually melting iron and hauling it around to fill cracks strikes me as really implausible. Some other, more easily melted metal perhaps, but not iron. Not unless my understanding of Roman metallurgy is really mistaken.

gfxxxx2• 2 years ago

Not only that, but the thermal stress of pouring molten iron on wet, cold and cracked stone.... call me skeptical

jandrese• 2 years ago

Count me as skeptical as well. Not only would it have been wildly impractical, but iron is prone to rusting and expands when it rusts. Plus it is slippery when wet. It's just not a good pothole filler.

blacksmith_tb• 2 years ago

Also seems like the stone around it would wear more quickly and then instead of potholes you'd have iron bumps in the road, not much of an improvement.

dukeofdoom• 2 years ago

They lived in really nice villas too. Frescos on the wall and mosaic floors. Better constructed than modern ones in some regards. No sqeeky floors for example. Surrounded by organic gardens with lemons and oranges and fragrant spices

kragen7• 2 years ago

most of the streets in the bustling seaside city were paved with silex, a type of cooled lava stone

'silex' is a rather old-fashioned word; nowadays it's more commonly called 'flint', which is a sedimentary rock, not an igneous one. https://en.wikipedia.org/wiki/Silex

processing taconite, a type of low-grade iron ore

taconite is typically 30%–35% iron, but it's true that most iron has historically been made from higher-grade ores than that (though throughout history iron has usually been made from lower-grade ores, just in much smaller quantities)

it is indeed fairly surprising to find cast iron in a roman town. china had cast iron from around 2500 years ago, but i thought the technology only reached europe during medieval times, and even later in western europe

OnlyMortal• 2 years ago

Flint like “churt” used to make tools way back when?

kragen7• 2 years ago

yes

Modified3019• 2 years ago

Huh, I would have bet $10 that flint was igneous. Given how glasslike it can be I thought it was related to obsidian.

Turns out it’s sedimentary, and I overlooked considering all the non-volcanic places it can show up naturally. I guess it’s time to brush up on my geology and mineralogy: https://en.m.wikipedia.org/wiki/Flint

jacobolus• 2 years ago

Your Wikipedia link says: "The word silex was previously used to refer to flint and chert and sometimes other hard rocks." Seems this was a fairly generic word.

According to http://doi.org/10.3764/aja.122.4.0579 which is the paper this blog post was based on, "The paving stones of Pompeii consist of a heavy, dark basaltic lava stone, which we describe as 'lava stone,' or silex, using the general Latin term. For local travertine stones, we use the common name, 'Sarno limestone.'"

One of the authors of the paper wrote a book, The Traffic Systems of Pompeii, which has: "When covered in gravel or created in beaten earth, the surface was calld glarea, but when paved in harder stones, the term silex was applied."

kragen7• 2 years ago

yes, the ancients often erred in their identification of minerals, lacking things like the flame test and spectrometers, not to mention atomic theory

thanks for finding the reference from the paper! it's puzzling that the article would describe 'heavy, dark basaltic lava stone' as 'a type of cooled lava stone that wore away relatively quickly'. basalt is one of the more wear-resistant rocks

ralferoo2• 2 years ago

'silex' is a rather old-fashioned word; nowadays it's more commonly called 'flint', which is a sedimentary rock, not an igneous one. https://en.wikipedia.org/wiki/Silex

From the start of the wikipedia link you yourself provided: "Silex is any of various forms of ground stone."

kragen7• 2 years ago

the next sentence says, 'In modern contexts the word refers to a finely ground, nearly pure form of silica or silicate' and then it goes on to explain that it historically referred to either flint or things that people confused with flint

jjk166• 2 years ago

This article is incorrect. The actual claim is that the romans were making repairs with molten ore, ie slag, which has a substantially lower melting point than molten iron and would be a cheap byproduct of iron production.

gfxxxx2• 2 years ago

Thank you. I was extremely skeptical that they used molten iron.

kortex• 2 years ago

I believe this is the article:

https://www.ajaonline.org/article/3863

In July 2014, we conducted a survey of Pompeii’s street network to document traces of iron that were observed on the stone-paved streets, which resulted in the identification of 434 instances of solid iron and iron staining among the paving stones. ... Pompeians were—in addition to using solid iron wedges—pouring molten iron and iron slag onto their streets as a method of emergency repair.

There's a huge gulf of difference between "a civilization is capable of melting iron" and "molten iron is so cheap and easy they used it to fill potholes".

Castable iron: Valuable, scarce, energy intensive, very hard to melt (comparatively), corrodes readily (especially on the coast)

Iron and other metal slag: Byproduct of iron smelting, basically waste, melts fairly easily, was used as ballast in ships, comparatively cheap, rusts superficially but is mostly a matrix of oxides which don't meaningfully react

I'm beyond skeptical that perfectly good cast iron was used to fill potholes. Using slag/dross/failed smelts/other byproducts of metallurgy makes far better sense.

It would be like far future archeologists unearthing rammed earth tire walls and concluding "the 20th century was so efficient at producing rubber they used excess tires as a building material" vs "they used a waste product which would have been landfill anyways".

kragen7• 2 years ago

and bloomery slag is always contaminated with bits of iron that never melted

aidenn0• 2 years ago

No iron melts in a bloomery; the slag is liquid and the solid bits of iron sink to the bottom of it. Blast furnaces melt the iron, but weren't found in Europe until much later than the eruption of Vesuvius (China was just getting them around this time).

tomcam• 2 years ago

Here in Seattle they do nothing. At this point I’d be happy if they filled them with chewing gum, crack pipes, and McDonald’s wrappers.

dinkleberg• 2 years ago

I wonder if this was just the doings of some eccentric in an act of euergetism (the wealthy supporting their cities through public works and the like) who thought that iron was just the thing. It was a resort city that attracted a lot of rich folk. It seems possible that rather than giving us insight into how the Romans maintained their cities it is just unveiling some small interesting idea someone brought into reality.

It is unlikely we'll ever know for sure. But it is interesting to contemplate how much of what we think we know about the past could be just way off and we've invested too much into artifacts of odd occurrences that just happened to survive while the more mundane and "real" are lost to time.

12thhandyman• 2 years ago

Badass article, super cool to think about filling pot holes with molten iron. Visited Pompeii with family when younger and one of the few things I remember “experiencing” were the wheel ruts while walking around. Very much makes sense now how difficult it’d be to fill in given the depth and width of the ruts; they’re expansive. Am not familiar with iron making but curious about iron slag. Welding slag is pretty light but if iron slag was used for ballast it must be substantial

Pompeii fixed potholes with molten iron (2019)

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