Technology and Terminology of Knapped Stone - IRIT
Technology and Terminology of Knapped Stone - IRIT
Technology and Terminology of Knapped Stone - IRIT
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• Thermal damage mainly covers : frost fractures, which can range from simple cracks<br />
to frost pits, or even to total fracture; variations in temperature combined with those <strong>of</strong> ambient<br />
humidity, giving more or less the same results (fig. 35); unintentional heat-altering, which<br />
produces "pot lid" fractures, crazed surfaces sometimes mimicking retouch on an edge, or clean<br />
fractures, accompanied by change <strong>of</strong> colour <strong>and</strong> lustre when the temperature exceeds 250°C.<br />
Such traces may be the only clues to accidental conflagrations or to ancient hearths.<br />
2.2. Mechanical device s<br />
Ranging from the plough to the bulldozer, present human activities cover ever larger<br />
surfaces, <strong>and</strong> affect ever deeper layers <strong>of</strong> the soil; lithic objects disfigured by mechanical contact<br />
with metal <strong>and</strong> <strong>of</strong>ten simulating retouch are therefore more <strong>and</strong> more common. Fortunately, such<br />
pieces are rarely free <strong>of</strong> specks or streaks <strong>of</strong> rust, <strong>and</strong> can also generally be detected owing to<br />
their multiple patinas.<br />
2.3. Humanly induce d alteration s<br />
Whether intentional or unintentional, heating can bring about the same visible alterations.<br />
There again, interpretation must rely on the chronological order <strong>of</strong> the facts : the systematic<br />
occurrence or high frequency <strong>of</strong> pieces altered by heating prior to retouching is strongly<br />
suggestive <strong>of</strong> heat treatment. However, there are documented examples <strong>of</strong> artefacts picked up (in<br />
the same way as tools with a double patina) after having been accidentally heat-altered because<br />
they happened to lie next to or under a hearth. Such artefacts can then have been used as cores<br />
or tool blanks.<br />
Intentional heat-treating <strong>of</strong> siliceous rocks in order to improve pressure debitage or<br />
retouch can at present only be inferred from the greasy lustre visible only on the part retouched<br />
after thermal treatment (fig. 68).<br />
Some alterations correspond to technical procedures : for instance, the blunting <strong>of</strong> the<br />
edge <strong>of</strong> a striking platform (see p. 131), the pecking or polishing <strong>of</strong> a pressure platform or <strong>of</strong> the<br />
debitage surface <strong>of</strong> a core, or even <strong>of</strong> the edge <strong>of</strong> a h<strong>and</strong>axe in the course <strong>of</strong> being shaped. The<br />
edge <strong>of</strong> a bifacial piece can also be deliberately blunted to prevent it from cutting, as is common<br />
in North America.<br />
Other alterations can be classified together with traces <strong>of</strong> use, such as the glosses <strong>and</strong><br />
polishes formed as a result <strong>of</strong> utilization, or the blunting <strong>of</strong> some Upper Palaeolithic burins.<br />
2.4. Addition s<br />
One must keep in mind that wood, resin, bitumen, leather <strong>and</strong> pigments, while not always<br />
visible, can be detected <strong>and</strong> analysed by means <strong>of</strong> microsampling (fig. 51). On the other h<strong>and</strong>,<br />
such elements may have resisted long enough for a double patina to develop, as in the case <strong>of</strong><br />
some hafted implements.<br />
One should therefore proceed with caution when washing the pieces <strong>and</strong> applying<br />
varnish in the course <strong>of</strong> marking.<br />
To conclude, there are unlimited possible combinations <strong>of</strong> such modifications, alterations<br />
<strong>and</strong> additions. The importance <strong>and</strong> complexity <strong>of</strong> surface conditions, <strong>of</strong>ten impossible to unravel<br />
during field-work, require minute observation during the laboratory phase, as well as extreme<br />
caution in dealing with archaeological material during <strong>and</strong> immediately after excavation.<br />
Blunders can irretrievably jeopardize certain observations <strong>and</strong> characterizations, particularly<br />
those concerning additions.<br />
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