sure, notice how he says things like "3 double handfuls of charcoal, 3 single handfuls of iron-bearing sand", or "dry fire for one hour before trying to smelt",

sure, notice how he says things like "3 double handfuls of charcoal, 3 single handfuls of iron-bearing sand", or "dry fire for one hour before trying to smelt", etc. Any time he mentions a number or a ratio, I guarantee it's hard-won knowledge that took ages to come up with (even if it was one of his ancestors that did it, and he just learned it from a book).