Fire scale is basically an oxidation of the surface and can be
very attractive. The problem is the oxide layer is very thin and
often difficult to control. If you look at old guns or swords they
are often finished with a beautiful and controlled oxidation,
commonly by case hardening or hot bluing. This has several
advantages other than attractiveness. It shows that the piece has
been hardened and in the case of a sword, tempred as well and the
finish give an barrier against corrosion.
Very interesting Nick,
I’d like to hear a little more about how an oxide layer can tell you
that a sword is tempered? Sure you can apply a torch to a blade and
watch colours run, but this is a long way off what I’d call fire
scale (maybe fire staining is a better term?).
The swords I make are either pattern welded or polished, I’d never
leave a functional sword in a coloured tempered state. I haven’t seen
every sword there is, so if you could point me to an example of what
you’re describing that would be appreciated.
Regards Charles A.