This Roman Gladius was a study of producing my own historical steel, in this case Shear Steel from Wrought Iron.
I packed these five bars of Wrought into a can (on the right of the photo) with bone charcoal and vegetable tanned leather, then welded the can closed on both ends with only a small weep hole to allow pressure to escape. To produce steel from iron in this way one needs to heat the can and its contents hot enough and for long enough to allow the carbon from the bone and the leather to penetrate into the iron. The iron never gets hot enough to melt, the carbon only penetrates the surface of the bars much the same as "case hardening" though with deeper penetration.
I started the can's soak in the gas forge while I continued working on another project, after a few hours I chucked the can and its contents into the wood stove where it stayed in our heating fire for 3 days.
After the Iron's long soak in the heated carbon I removed the bars from the can and forge welded them together on edge to form the core of the sword. Here you can see where I have cut and polished the forge welded stack - one can clearly see the dark carbonized edges of the bars with the soft iron still in the centers.