Thursday, February 16, 2012

Why? A Historical reference.

(Day Two)

So - why is important that someone is working with bloomery iron?

It is fair to say that to understand were we are going, there needs to be a consideration of where we have come from.

The following is altered from a much longer commentary I wrote this morning for the NORSEFOLK discussion group.

First (and most importantly) the standard metal used up to the Medieval Period is *bloomery iron*. This metal is soft, has a stringy texture with slag inclusions. Individual pieces would vary considerably in physical consistency. Carbon content would vary not only from piece to piece, but also *within an individual bar*. We modern smiths are completely dependant on mass produced, scientifically refined, industrially consistent (cheap!) metal alloys. These are produced using variations on the Bessemer furnace, only introduced in 1855.
There is a fuller commentary on 'traditional' versus modern metals on the main Wareham Forge web site : 'Wrought Iron - what it really is, what it really means'
(I get very aggravated by contemporary bladesmiths who have adopted bloomery iron making, building on the work of those who developed the current methods being used - and obviously not understanding them. Making bloom iron is *not* about alloy control, it is about creating a physical texture in the metal.)

Modern commentators looking at traditional practices often use the term 'ritually' in place of a better description 'based on experience'. Our concept of 'ritual' is most certainly far different than ancient / non Western concepts. 'What you do if you want things to work' - in our world we would call this science.
An experienced smith knows that when you quench different pieces of iron metals from orange in water, there can be changes in how it breaks when cold hammered. The exposed surfaces can have different colours and textures. Metal that is thus treated, then found to be brittle, have a surface of small crystals, and a bright, light grey colour - that material also makes for a hard / durable cutting edge.
(This selection of materials based on physical appearance is the core of the Japanese traditional method. Consider - How do you spark test for carbon content, a standard modern practice, in a world with no high speed grinding?)

This wide variation in the quality of the starting metal is vastly important when creating cutting edges. Examination of a large number of individual blades from the Roman to full Medieval periods has shown that the processes of quench hardening and drawing back temper were *not* universally applied by bladesmiths until much later than most would suppose. Although this fact seems counter intuitive to a modern blacksmith, my interpretation is that the variation in metal characteristics in bloomery produced iron is the reason.

Even a small 'short shaft' furnace is easily capable of producing raw iron blooms much lager than those typical of the few artifact blooms we have from before the introduction of water power (Europe, roughly 800 - 1100 AD). Early smelters were creating blooms in the 5 - 8 kg range, *limiting* potential size. This just because of the great difficulty of attempting to work larger masses of metal down to useful bars, with only stone anvils and hand powered hammers for tools.

'Redemption' Bloom - November 2006
6.8 kg, from 19 kg combined ore and gangue

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February 15 - May 15, 2012 : Supported by a Crafts Projects - Creation and Development Grant

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