Fire Steels - in theory?

(Taken from an ongoing discussions related to a research project on Viking Age / L'Anse aux Meadows and Vinland beyond / Flint & Jasper strikers / Fire Steels)

I freely admit that making fire steels has * not * been my best thing in the past.

Like many apparently simple things, the metal selection, and actual heat treating, for best results in fire steels is complex.

Quickly (as I understand it) :
The way these work is that the steel resists the tearing action of the stone. The pressure required eventually tears off a splinter, which due to the force heats under impact. Hot enough to actually heat the fragment above the 'burn point' of the steel. This makes the spark, with temperatures in the 1100 - 1200 C range.
Different carbon contents have different shear strengths.
Different carbon contents also have different burn points
You can modify the shear point (strength / hardness) of any one given alloy (carbon content) based on the quenching method chosen.
Different stones themselves will break with different applied force.
So this suggests there is a dance between metal type, making method, and stone selected - combines for best results

Generally my understanding is that a good fire steel would have a high carbon content to the alloy. Here meaning at least 0.05 % (spring), but maybe as high as 0.1 % (file).
But the quench may slightly on the slower side, to keep the result from becoming so hard the stone chosen can't actually shear off that small flake.

(I took a fast look over the past blog entries - as I thought I had worked up something on the topic. Yup - based on something the same researcher had asked about back in 2011! )
https://warehamforgeblog.blogspot.com/2011/04/this-came-in-from-my-friend-and-mentor.html

   " I may order 2-3 fire-strikers from a couple of sites on Etsy that
   are selling Viking Era types (one site is a forge in Canada, the
   other's in Germany). Those might get us started with some basic
   experiments on how the jasper / chert responds (how many flakes and spalls are generated per 100 strikes, etc.) and of course we'll make
   some sparks, even if we don't have information on the carbon content
   of the steel. "

(site references deliberately removed!)

I think it illustrative that the Canadian chosen does NOT refer to the actual metal type used.
The German does state 'carbon steel' - which is what is needed for correct function.

from Marstein, Uppland, Norway : 7.7 cm. Common 'boat shape' forged from flat bar (Image from 'Viking Artifacts' - Graham-Campbell)

The German also is offering shapes that look more like the actual artifacts I am familiar with.
For this reason I would suggest the German (shipping is the only cost variable).




Readers may have seen way too many things as being named 'Viking' - when in fact they are not even remotely like the real objects! This is a *big* problem for me. Truth before Advertising please!