- Ironworking in the Celtic World -
resilience of the iron. The idea of quenching the metal may have come from work-
ing sheet-bronze which, after being heated to anneal it, is cooled by being plunged
in water. Similarly, tempering is so similar to the annealing of work-hardened bronze
that it might have been thought an obvious method of softening steel which had been
overhardened by quenching.
The existing evidence suggests that by the later Celtic period the advantages of
quenching were appreciated by some smiths producing edged tools and weapons.
Metallographic examination of iron age ironwork has shown that the amount of steel
used varies considerably; most smiths worked with wrought iron containing very
little steel, a perfectly satisfactory metal for most purposes. Where steel had great
advantages was for weapons and edged tools, and the evidence indicates that by the
end of the first millennium Be it was being used for these, although not invariably.
Perhaps the simplest way of utilizing steel in weapons was to weld bars of steel
and wrought iron together to produce alternating bands across the blade, a technique
seen in one of the sword blades from the late iron age hoard from Llyn Cerrig Bach,
Anglesey (Figure 17.1). Even without quenching, such blades had advantages over
wrought-iron blades, and metallographic examination shows that often they were
not quenched. A more advanced technique was to weld the bars together to form a
blade with a steel edge sandwiched between layers of wrought iron, or a thick steel
skin encasing a core of wrought iron. Here quenching enhanced the effectiveness of
the blade by hardening the steel, but the wrought iron in it made tempering unnec-
essary. Such blades have been found in central European oppida dating from the end
of the first millennium and mark a high point of Celtic smithing.
It is important to remember that the Celtic smith lacked our knowledge of the
mechanisms which controlled these changes. He was aware that certain actions pro-
duced certain results, but how far the knowledge of processes such a carburization
and quenching was disseminated remains uncertain. The fact that pieces of almost
pure wrought iron were quenched, while pieces of steel were left unquenched,
suggests that confusion was common. For most smiths working with wrought iron
containing little or no steel, quenching, let alone tempering, would have been an
irrelevancy.
The evidence which we have suggests that the Celtic blacksmith acquired his raw
material in a prepared form, and that the smelting and preparation of the iron was
separated from the fabrication of the artefacts. Much of the newly prepared metal
was traded in the form of bars. On the Continent these usually took the form
of square-sectioned bars tapering into a long spike at each end. In Britain they
were the so-called currency bars, named from a passage in Caesar's De Bello Gallico
(v.I2) where he refers to the Britons using iron bars as a form of currency. The
commonest form is a long, flat bar with a flanged socket with, in some cases, its tip
folded back and welded to the body of the bar. Both forms seem unnecessarily
elaborate for metal which would have been reworked as soon as the smith had
acquired it, but, as Peter Crew has noted, the fact that the iron had been thinned,
turned and welded guaranteed its quality, and in a period when bad as well as good
ores were smelted, smiths would have welcomed such assurances. As well as material
obtained from the smelters, large amounts of scrap iron would have been utilized.
This was always an important source of material for the smith. Iron artefacts are
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