Planning to write a story. I was wondering if it was plausible that (with a decent understanding of how the thing works), if you could build a crude Bessemer converter using only technology available in the late medieval period (1300s-1400s).


1 Answer 1


A bessemer converter is a device intended to convert bulk high-carbon molten iron into steel, on the order of 5 to 30 metric tons at a time. The converter itself was a cast iron structure lined with ceramic, which would itself have been very difficult to produce in the 14th century, and even if it was possible to construct a bessemer converter, it would have been very difficult to produce sufficient quantities of high carbon iron at a sufficient temperature to load into the converter, and similarly difficult to produce a sufficient flow of high-pressure air to bubble through the liquid metal.

My feeling for this problem is that advances would have to be introduced to iron and steel manufacture along the entire iron production chain, and it would not be practical to simply introduce the bessemer converter.

  • $\begingroup$ What about if advances were made to cast iron production technology, so that it was brought to a similar level as that of 14th century china (with blast furnaces and what not)? $\endgroup$ Commented Sep 2, 2023 at 6:16
  • $\begingroup$ As my answer says, you'd have to improve the entire production chain to be able to produce sufficient masses of iron at sufficient temperature, with sufficient high pressure air. If you can achieve that, then the bessemer converter is the next piece of the puzzle. $\endgroup$
    – Monty Wild
    Commented Sep 2, 2023 at 6:28
  • $\begingroup$ Assuming all production chain issues aside, and with the aforementioned cast iron, would it reasonably be possible to build a bessemer converter? $\endgroup$ Commented Sep 2, 2023 at 6:30
  • $\begingroup$ With sand-casting for the cast iron and ceramic fire bricks, plus some knowledge, I expect so. The main limiting factor is going to be supply of sufficient amounts of sufficiently hot iron and enough air. $\endgroup$
    – Monty Wild
    Commented Sep 2, 2023 at 6:37
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    $\begingroup$ don't forget a Bessemer converter needs large scale cast iron which took a long time to develop early cast iron is far to inconsistent to be cast into large strong shapes. large scale casting took a few hundred years to workout. You also need large quantities of high purity fuel. $\endgroup$
    – John
    Commented Sep 2, 2023 at 21:34

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