Manufacturing tools by chipping away the mass follows a linear trajectory of reduction. Each flake removed is one step toward finishing a tool. The key to chipping cryptocrystalline materials is to control the breakage and guide the fracture path in such a way that the mass is reduced and the impact damage is carried away by the resulting flake. The flake retains the bulbar features of the impact, leaving only the negative bulbar features on the core. Mistakes, such as inadvertently damaging the mass or core during flake removal, can be made at each step, however, these could halt the process and ruin the piece. These ruin pieces provide critical evidence of the manufacturing trajectory since failure can occur at any point in the reduction process. Failed pieces leave traces of the methods and strategies of tool manufacture and provide very important technological information and insight into the manufacturing trajectory and intent of the flintknapper (Figure 1).
Controlling the direction of fracture originating from the Hertzian cone of force is the key to shaping stone tools. The intent is to direct the fracture path along a trajectory that literally sculptures the finished tool. A critical step in controlling the fracture path is proper preparation of the striking platform - that point on the surface of the core which will be struck by the percussor (hammer stone, bone or antler billet, punch, or pressure flaking tool). Proper preparation of the platform by strengthening it by trimming or grinding will increase the probability of a successful flake
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Figure 1 Anatomy of hammerstone-struck flake. 1, Bulb of percussion; 2, striking platform; 3, proximal end; 4, distal end; 5, exterior or dorsal surface; and 6, interior or ventral surface.
Figure 2 Illustration of hard-hammer percussion that produces a Hertzian cone fracture initiation.
Removal. Improper preparation, on the other hand, will increase the odds of failure. Failure can occur at any point in the manufacturing trajectory of a chipped stone tool, or at any time a flake is removed. Failed efforts provide important technological information to archaeologists because each failure freezes the reduction trajectory at that point. Often the technique, strategy, and style of the ancient flintknapper can be seen in a failed piece better than in a finished piece. Finishing a stone tool often removes the traces of previous reduction steps.
Several techniques of reduction may be employed during the course of making a chipped stone tool, depending on the stage of reduction and the attributes desired for the finished product. How the fracture is controlled is also partly due to the type of implement used. A hard percussor, such as another stone, creates a typical Hertzian cone when contact is made with the core. Characteristic attributes of a cone-type of fracture initiation are the round impact scar at the top of the cone on the striking platform, striking platform remnant, a strong bulb of force, and a relatively thick bulbar cross section. This type of percussor requires a strong striking platform to insure proper flake removal. If the platform is too thin the hammer will crush the edge and often ruin the piece. A crushed edge also dispenses the energy of the blow. The advantage of using a hard-hammer percussor is that it allows a flintknapper to take the initial steps of breaking a mass and creating pieces such as large flakes or preformed core for further reduction, or removing flakes from a core to be used as blanks for further reduction. Thinning a biface using a hard hammer is difficult because of the strong platform necessary for successful flake removal. Usually this is not possible when the objective is a small biface 10 cm or less in size such as a projectile point. Exceptions do occur. For example, the ancient Maya in northern Belize made massive bifaces, most were used for axes, but huge symbolic bifaces (‘eccentrics’) up to 75 cm long were also made from the massive chert outcrops for which the area is known. In the Maya case, stone mass worked in favor of the flintknapper in thinning large bifaces using only limestone hammers. The Maya resolved the hard-hammer problem by creating a 90° striking platform by beveling the edge which provided the necessary contact surface for the stone hammer. The thickened edge withstood the hammer blow allowing large thinning flakes to be removed from the faces of the biface (Figure 2).
Striking the edge with a soft percussor such as an antler billet creates a bending type of fracture initiation. A Hertzian cone fracture is not the result of a soft hammer, although an attribute of a Hertzian fracture may occur such as a slight bulb of force. Controlling a bending fracture initiation also requires critical attention to the striking platform and existing flake scar ridges created by the removal of previous flakes. Strengthening the platform is done by dulling the edge either by raking it with a hammer stone or grinding the edge with an abrasive stone. The flint worker will select a place on the biface edge where a ridge was created by the intersection of two flake scars. The ridge provides a reinforced point that is ground or strengthened. The intent is to use the flake scar ridge to direct the fracture path across the surface of the biface at least to mid-point or beyond. This is the most basic method of thinning a biface intended for use as a knife or a dart point.
The resulting soft-hammer flake will have a characteristic lip at the striking platform. This lip is the result of bending the edge of the biface to the point that it fractured. A diagnostic ‘biface thinning’ flake is created that is usually thin, arched in profile, has a lipped striking platform, and facets from previously removed flakes on the exterior surface. The ideal biface thinning flake is not always the result of soft-hammer flaking. Crushed or snapped striking
Platforms occur frequently, and sometimes there is no discernable lip at all.
Archaeologists have debated the pros and cons of hard-hammer and soft-hammer flaking for years, because under certain circumstances a bending flake can be removed with a hard hammer, and a cone-initiation flake can be produced with a soft hammer, but these instances are not frequent enough to define a technological pattern. Modern-day lithic replicators use stones or heavy copper billets for hard-hammer flaking, and copper billets for soft-hammer flaking. The copper is a substitute for antler billets, which wear out frequently and have to be replaced, whereas the copper will last for decades. Prehistoric flintknappers did not have access to copper for billets and primarily used antler, bone, or ivory where available.
Another effective method of reduction is the use of indirect percussion requiring the use of a punch. The punch is usually an antler tine or bone, shaped for the purpose. The punch is precisely placed on the striking platform and tapped with a hammer. This technique was probably more widely used than archaeologists have recognized, but there are advantages and shortcomings to the technique. The advantage is one of control, especially if the flintknapper is removing blades from a prepared core. Precision in impacting the core striking platform is critical to successful blade removal. The punch can be precisely placed on a ridge that will guide the fracture path through the core. The same advantage holds true when a punch is used to thin and shape a biface. The disadvantage comes with the difficulty of securing the core or biface sufficiently to withstand the punch blow. If the core or biface is not well secured, it will move and the movement will dispense the energy from the blow and no flake will result. Punch blades and flakes often display slight lipping and bulbar features because the punch flake can be initiated by a bending fracture, but the compressive force also produces a slight bulb of force. The striking platforms for both blade cores and bifaces were often strengthening by grinding or abrading.
Most finely made bifaces were finished and shaped by pressure flaking. Pressure flaking has the same advantage as indirect percussion in that the flaking tool can be placed precisely on the platform. Flint workers then apply pressure using various techniques of applying force, either with the hands and forearms, or by placing the elbows inside of the knees and using leg pressure to assist the hand and arm pressure. Pressure flakes have similar characteristics to punch flakes in that there are often subtle lips and bulbar features, but are smaller than punch flakes. Small bifaces such as arrow points were made entirely by pressure flaking as were some small thin dart points (Figure 3).
Figure 3 Illustration of pressure flaking.
The products of core-blade technology are found in many sophisticated stone technology systems where appropriate raw material was available, namely fine grained chert, flint, obsidian, or quartzite. Blades are prismatic flakes removed from prepared cores that are over twice as long as they are wide. Blades make highly efficient cutting tools as well as blanks for a variety of other tools such as awls, perforators, end scrapers, burins, and cores for the production of burin spall tools. To produce a blade core, the nodule was prepared by creating a suitable striking platform with an appropriate angle of about 70-80°; platform preparation depended upon the type of percussor used, whether a hammer stone, billet, punch, or pressure. With any technique, the flintknapper had to ensure that the platform and outer surface met at the appropriate angle; if not, then such an angle needed to be created. Next, the flintknapper needed to create an intersection of a ridge created by the removal of one or more flakes down the face of the core. The ridge is critical in directing the path of the blade as the fracture propagates down the core. With hard-hammer blade removal, the critical factor is to remove any overhanging platform remnant created by the removal of previous flakes. Use of a hard hammer creates prominent negative bulbs that often leave such an overhang. With billet percussors, the overhang not only needed to be removed, but the edge of the platform needed to be strengthened by grinding. This helps prevent step or hinge fractures that would otherwise ruin the core. The same concerns also needed to be addressed with indirect or punch percussors. Obsidian platforms used in the pressure removal of blades were often abraded to create tiny surface flaws that aided in initiating fracture during blade production. Blade cores have the diagnostic polyhedral shape created by multiple facets resulting from blade removal.
Fluting is a form of blade removal. Flutes are channel flakes removed from the base of a biface to thin the haft element. To prepare a biface for fluting, the late-stage preform was thinned in such a way that the longitudinal midsection was the thickest part of the biface. This subtle ridge served to guide the fracture path of the channel flake much like a ridge on a polyhedral blade core. The striking platform was prepared at the base by either retouch or grinding to strength the edge. The flute was removed on one face possibly using one of several techniques such as a billet, a punch, or even pressure. The preparation and removal of the flute was repeated on the opposite face. Failed attempts to flute a point included several problems, the most common of which was the end shock or snap that broke the piece in half. Another was an overshot flute that terminated through the piece prematurely, literally splitting the preform. Other failures were caused by collapsed platform, hinging or stepped flakes that also terminated prematurely. Failed attempts at projectile point manufacture usually mark site or location within the site where flintknapping took place. Finished projectile points, on the other hand, may be recovered hundreds of kilometers from the point of manufacture. Fluted projectile points are most widely identified with the Clovis and Folsom complexes in North America.
Bipolar flaking is yet another method of reducing a mass into sharp-edge flakes or flake blanks. A pebble or cobble is placed on an anvil, such as another stone, and smashed on top with a hammer stone. The resulting impact causes the core to be subjected by forces from two directions, much like cracking a walnut placed on an anvil. The attributes of bipolar flakes and cores are much different from those created by previously described methods. Flakes are removed from the exterior of a nucleus. The nucleus exhibits crushing and direct impact scars on both ends. Bipolar flakes are often trapezoidal or thin slivers with crushed platforms. The disadvantage of bipolar flaking is that the stone worker has little control over the products. The advantage is that round pebbles and cobbles that lack sufficient facets or angles for hard-hammer use can be fractured by the bipolar method. In cases where small pebbles are the only resource available, it allows the knapper to obtain sharp-edge flakes or cores for the use in cutting tasks. Bipolar technology is often found in areas where the only available resource occurs in the form of small pebbles (Figure 4).
World History
