Is this actually true? Because all the YouTube videos I’ve seen of people trying to make iron in primitive ways have the issue of too much carbon in the iron. This causes the iron to be very brittle and hard to work. The trick about making good steel is to get just the right amount of carbon.
You know you are in for a good time when you get to the chapter called “Sexual connotations”.
I’m not an expert on the field, so I’ve read the paper, but am not qualified to draw conclusions from it. But as I read it, the focus is more on the role of ritual and religion in the making of the iron. And the transfer of knowledge through this process and hypothesize the addition of the burning of bone is actually beneficial.
However they do not approach this from a material technology standpoint. So I would love for someone with knowledge on this point to chime in. It’s very interesting if the people back in the day knew how to make low carbon iron and the little bit of carbon they did add came from the burning of the bones. But as I see it the burning of the bones is more a ritual kind of thing and getting all of the carbon out of the iron is the harder thing to do, not putting the carbon in.
Bone char isn’t super high carbon, so it’s possible that either the calcium phosphate or calcium carbonate is playing a roll.
But honestly, you’re probably not getting very much of it mixed in from primitive smelting or forging methods.
You need >700C to decarburise iron you don’t need much for that but coal and a fan, i.e. a bloomery. Pretty much defines the beginning of the iron age. Getting very low-carbon iron is quite easy, you just need enough fuel and air, the trick is then adding the right amount of carbon back. Also, getting rid of impurities, slag inclusions, etc, long story short: Lots of hammering and folding different carbon grades together, though some work can be saved by building very large bloomeries and processing very large batches producing quite slag-free low-carbon iron which then can be case-hardened.
The way out of that is crucible steel, melting your ingredients in an air-tight crucible, but that requires advanced furnace technology that somehow noone came up with before industrialisation, with the exception of India. The banding btw is due to alloy not production method (though you need to follow specific steps to bring out the banding).
