Workshop 5 - Flake Scars and Flaking Techniques
In Workshop 4, we looked at platform types that occur on flakes, along with other attributes, such as finials, detachment scars, and demicones.
In Workshop 5 we will examine how different types of flake scars on tools relate to the flintknapping techniques that produced them. These are introduced in the Techniques pages.
As you read through the workshop, note that the criteria for differentiating between flintknapping techniques are based on qualitative assessment of attributes and combinations of attributes. A qualitative assessment relies on the quality of the attribute—its shape, appearance, etc.
The difficulty of qualitative assessments is that the hallmarks of flintknapping techniques tend to vary considerably in appearance, complicating their identification. This is due to equifinality—two different processes creating similar-looking attributes.
For instance, large pressure flakes can sometimes look like soft-hammer biface thinning flakes; or hard-hammers can sometimes produce the hallmarks of soft-hammer flaking. The way around these issues is to do modern experiments as an aid to identifying hallmarks of techniques and to explore how much those hallmarks vary, and to gauge the level of uncertainty in a qualitative identification.
However, translating experimentally-derived knowledge to usable definitions has proven tricky in some cases, as you will see in the examples that follow. Nevertheless, qualitative assessments are the foundation for description and classification not only in lithic studies, but in archaeology generally.
Qualitative assessment differs from quantitative assessment, which relies on the measurement of amount. Attempts have been made to define qualitative criteria using quantitative methods—for instance, identifying hard-hammer flaking assemblages based on the size distribution of the flaking debris—but few of these empirical studies have proven useful because of the complexities of how attributes are expressed.
Measurement alone is a gross tool, one that does not capture the nuance of interacting variables. While the sophistication of quantitative analysis in lithic studies has increased substantially in recent years—many contemporary lithic studies are almost entirely quantitative in approach—it is important to understand that quantitative measurements always follow on from qualitative classifications.
Tip: hit the play button to load the 3D model. You can now rotate the model as you read the text on the left.
Direct hard-hammer percussion
Hard-hammer percussion flaking is the most common technique seen in the archaeological record. The history of technology began with the technique some 3.2 million years ago, and our hominin ancestors mastered the technique by 2.6 million years ago. Hard-hammer percussion is essential for breaking up larger stones into flake blanks and cores, and it was used in early stages of reduction in even the most complex technologies.
'Direct' hard-hammer percussion refers to a technique where the core is reduced by striking the platform directly with a hammerstone, as opposed to striking an intervening punch, as with indirect percussion. 'Hard' hammers were made from resistant stones such as igneous, volcanic, or metramorphic rocks, in contrast to soft hammerstones made from limestone or sandstone.
This model is a chert macroblade core that displays the attributes of hard-hammer percussion. If you rotate the model so you are looking down on the platform, you can see how the percussion blows were delivered well-back from the edge of the core. This is characteristic of flaking with a hard hammer. Soft hammers were more commonly used in striking directly on the core edge, rather than back a distance from it.
Another hard-hammer characteristic is the relatively deep negative bulbs at the platform ends of these flake scars. Hard-hammer percussion initiates flakes conchoidally, usually resulting in pronounced bulbs of force.
The hard-hammer blades in this model and this model also display the characteristics of hard-hammer percussion. Both have clear attributes indicating conchoidal initiations--e.g., eraillure scars, umbo, prominent bulb of force--from blows delivered well-in from the edge of the core. The pencil line on the platform of the first model sketches the distance from the edge of the core to the point of percussion that detached the flake.
The Australian pebble-edged core in this model was also made by hard-hammer percussion. The main characteristic that indicates this is the way the flake scars are relatively deep, with a 'scooped out' appearance. This is a 'core tool' and the flaking was mainly done to produce a sharp cutting edge on this water-rolled cobble, although the flakes may have also been used as cutting tools.
The Levallois Method was a sophisticated way of producing flake blanks for tools using hard-hammer direct percussion. This Levallois core from Germany was reduced around the perimeter by striking flakes off with a hard hammerstone. The deep percussion scars resulted from the pronounced bulbs of force created by the hammerstone.
Direct soft-hammer percussion
Soft-hammer percussion was accomplished with a soft material, such as antler, bone, wood, or soft stone such as limestone or sandstone. The earliest evidence for soft hammer percussion dates to the Late Acheulean, when bone hammers were used to make bifacial handaxes.
Soft hammers are ideal for thinning a stone tool. Then the platform is struck on the edge, the stone bites into the soft material. This prolongs the contact time, and the force is released more slowly into the stone. The impact is less jarring than with a hard hammer, and the edge of the core often wrenches away in a bending initiation rather than a conchoidal one.
Since a pronounced bulb is not produced in bending initiations, the profile of the flake tends to be flatter. Because of these various factors, more refined flaking can be accomplished with soft hammers than with hard hammers.
The Caddo biface in this model is considered one of the finest known examples of soft-hammer percussion thinning. The flakes were struck by landing forceful blows directly onto the edge of the biface, but without breaking it. The flake scars expand outward from the platform edge, a characteristic of soft-hammer thinning. The cross-section of the scars is very flat; compare them, for example, to the scars on the Levallois core in the previous model.
For a similar example of masterful soft-hammer thinning, view this model of a laurel leaf biface from the Solutrean period in France. Note the similarity in the expanding shape and flat profile of the thinning scars.
Now have a look at this model of a stone axe blank from Australia. Many of the scars around the perimeter of this blank have relatively deep negative bulbs of percussion, but the platforms were likely quite shallow, with many and perhaps most flakes struck by blows onto the platform edge.
Review the model's annotations, focussing on the long end-thinning scars. Removing such invasive flakes from relatively acute-angled platforms using a hard hammer is very difficult, but is straightforward using a soft hammer. Indeed, in the hard-hammer Levallois Method, the flintknappers created steep platforms for off-edge percussion to achieve a similar degree of invasiveness.
This flake is from the same quarry as the axe blank. The flake initiated by bending from a blow delivered directly onto the platform edge, which the flintknapper abraded to make it stronger. The profile of the flake's ventral surface is relatively flat, consistent with a bend initiation. These flake attributes are typical of soft-hammer, on-edge percussion thinning.
Australian flintknappers did not have access to antlers, but historically people in the Kimberley region, on the opposite side of the continent, used soft hammerstones for on-edge percussion thinning and shaping of bifaces. The flat faces of hardwood boomerangs were widely used in Australia to retouch and resharpen flake tools, and some of the best hardwoods for percussion billets anywhere in the world are widely available in Australia. Based on this evidence, it seems likely that the axe blank was made by soft hammer percussion using a soft hammerstone or hardwood billet. Unlike the Caddo biface, inferring the flintknapping technique for this axe blank is not straightforward because the flake scar evidence is ambiguous.
Now review this and this Australian stone axes from the Lake Moondarra quarry in Queensland. The stone is a very tough material called metabasalt, yet the flintknapper was able to expertly thin and shape these very large bifaces by striking off long, flat invasive percussion flakes (the scars are partly obscured by subsequent grinding). So now look at this stone adze made recently in New Guinea. We know from historical accounts that these axes were made by direct hard-hammer percussion, and you can readily see how the scars are far less flat and more 'scooped out' than the flake scars on the Lake Moondarra axes. A working hypothesis is that the Lake Moondarra axes were also made by soft-hammer percussion, but further analysis of the flakes at the axe quarry will be necessary to evaluate this.
For a modern example of masterful on-edge direction percussion using a soft hammerstone, watch this video. The biface made in the video can be viewed here.
Indirect Percussion, Bifacial
For many decades archaeologists excavating in the United States recovered short pieces of bone or antler from prehistoric sites that they referred to as 'drifts', named after a punch-like tool used in metalwork. Many early archaeologists considered drifts to be punches for indirect percussion flaking, but as experimental flintknapping took off as a research method in North America in the 1960s-1980s, most researchers used direct freehand percussion with antler billets to replicate bifacial tools. This practice continues today.
However, many of the early historical accounts of flintknapping in North America explicitly described bifacial flaking using an indirect percussion technique with short bone or antler punches. The Karuk flintknapper Ted Orcutt flaked obsidian ritual bifaces with antler punches into the 1940s, and Lacandone people in Mexico and Guatemala used antler punches for blade-making into the recent past.
Flintknappers in North America are now starting to turn to indirect percussion to make replicas of bifacial stone tools, but this has yet to be explored by archaeologists. For bifacial technologies, it is unclear how and to what extent the attributes of direct soft-hammer direct percussion flaking differ from the attributes of indirect percussion flaking using a punch ('punch-flaking')—more research is needed!
One benefit of punch-flaking discovered by European flintknappers experimenting with blade-making and quadrifacial reduction is that the technique can be used to manipulate the way the flake terminates. This is discussed later in the workshop. In the case of bifacial punch-flaking, the technique lends itself to creating a prominent midline down the centre of a biface by striking off relatively large thinning flakes.
Now have a look at the biface in this model. To better see the flake scars, open the sidebar menu, open 'Surface', and turn the 'Use Texture' to 'None'. The model now has a silver render. Rotate the model and tilt the base upwards to catch the shadows. Note how the flake scars vary in width and have fairly prominent undulations. Some of the scars are relatively concave in profile. These attributes suggest that the scars were not produced by pressure flaking, which we will review below.
The flake scars also end right at the centreline of the biface, and controlling the location of flake termination this precisely is very difficult to achieve with direct percussion. Direct percussion is more likely to drive the flakes past the centreline because of the way the biface is supported. The prominent ridge down both faces of the tool in the model, probably achieved by punch-flaking, provided a relatively thick but strong tool, and, compared to pressure flaking, the attrition caused by the larger bulbs of force ensured a sharp cutting edge.
Notches were sometimes made on stone tools to haft them to organic shafts and handles. The notches provided a recess to receive the binding. Notching became particularly elaborate in North American toolmaking traditions, particularly during the Early Archaic period in the eastern and midwestern part of the continent.
While notching small, thin tools, such as arrowheads, can be accomplished by pressure flaking, flintknappers often drove exceptionally deep notches into relatively thick bifaces. This was done using an indirect percussion technique, by striking a small antler or bone punch set at the apex of the developing notch.
The notches in this model of a stone knife from Alabama are narrow and deep, and curve slightly. The minimum width of the notches, about 3 mm, indicates the thickness of the punch, probably a bone splinter or perhaps a ground-down antler.
Now view the scars at the apex of the notches on each side of the point. Three of the last four notch scars ended in a step termination, or nearly ended in a hinge. This suggests a relatively large degree of force was used to initiate the flakes, consistent with an indirect percussion technique.
Also, the notch flake scars are relatively large, and a significant amount of stone was removed by each one. This, too, indicates an indirect percussion punch was used.
Similar notch flaking scars--also make by indirect percussion--can be seen on this model and this model.
Indirect Percussion, Quadrifacial
Stone axes and adzes with rectangular (quadrifacial) cross sections were made in Europe, Indonesia, and the Pacific. Each face of the rectangle was flaked from two directions, and the corners of the rectangle are bifacial edges. The faces are oriented at close to 90 degrees to each other.
Modern flintknappers in Europe have experimented extensively with replicating these axes, but a frequent problem encountered with direct percussion is that the flake would travel across the face and lop off the opposite edge (an overstruck termination, reviewed in Workshop 3).
The solution was to use an indirect percussion technique. An antler punch could be held at an extreme angle to the platform to maximise the amount of outward force. When done correctly, this caused the flake to terminate at or just beyond the centreline of the face while maintaining a right-angle between the faces. This ingenious and effective solution was discovered independently by flintknappers in Indonesia and the Pacific. Indirect percussion antler punches are found on European sites where axes were made.
The quadrifacial axe blank in this model was rejected in the early stages of manufacture. Note the very deep negative bulbs of force; this reflects an aggressive approach intended to remove stone relatively quickly. The punch was angled to deliver considerable inward force as well as outward force. The hinges induced from one edge were removed by striking flakes from the opposite edge; this was possible because the faces are relatively narrow.
The punch was seated on a hinge termination in one location, and a flake was driven through the hinge to the opposite edge. A flake removal in another area was miscalculated, and it propagated completely across the piece and removed the opposite edge. This may have caused the rejection of the blank as re-establishing the platform would have been difficult and may have changed the desired proportions. Consult the Annotations menus to see pins marking these features.
The rectangular-sectioned axe in this model is a finished version of the axe in the previous model. The flake scars on the two broad faces of the axe have been ground smooth in preparing the cutting edge, but the flaking scars can still be seen on the axe's sides.
Note the smaller size of the scars relative to those in the previous model. Several of them have propagated completely across the sides of the axe without compromising the rectangular section.
The axe in this model is smaller and unground. The edges in this case were finished by pressure flaking along the platform edges.
This axe blank is a replica made by the flintknapper Marquardt Lund by indirect percussion using an antler punch. Note the similarity in scars between this replicated example and the previous model.
Indirect Percussion, Blades
Indirect percussion was used extensively in Europe and Western Asia to make blades--parallel-sided flakes that are more than twice as long as they are wide. These blanks were used for a variety of purposes.
Indirect percussion is an ideal method for blade-making because of the precise way a flintknapper can manipulate the downward and outward forces necessary to initiate a flake and ensure its propagation along the core face.
With freehand percussion the flintknapper must simultaneously control the downward and outward forces, and the point where the flake initiates, through the way they swing the hammer. While this can be a remarkably skillful process by an accomplished flintknapper, there is always some margin of error due to the vagaries of hand-eye coordination.
With indirect percussion, the flintknapper can control each of these variables independently, based on the placement and angle of the punch. The tip of the punch is where the flake initiates, and this can be aligned precisely with the mass on the face of the core, and at the perfect position on the core platform. If more inward force is needed, the punch can be angled closer to parallel to the core face. If more outward force is needed, the punch can be set at a greater angle relative to the core face. The amount of force is calibrated by how hard the end of the punch is struck. In contrast, in direct percussion, all four of these variables are determined simultaneously by how the flintknapper swings the hammer against the platform.
Consider this indirect percussion blade core from France. Note the straight and almost perfectly parallel arrises (ridges between the flake scars) on the core face. Also, note how there are almost no undulations on those flake scars. These attributes imply precision of a degree that is impossible to achieve by direct freehand percussion.
Next, access the Annotations by opening the side bar. Review the pattern of blade scars shown by the pins. While it is possible to follow a similar pattern in freehand percussion-flaking, indirect percussion flaking allows greater precision in striking behind zones of high mass.
Now consider the indirect percussion blade in this model.
The blade is trapezoidal in cross section—the same morphology as the hypothesised blades explained in the previous model's annotations.
The blade margins are less straight than the margins in the core model and are closer to what can be achieved by skillful freehand percussion. However, the small platform, and point of force application precisely positioned behind the central scar, suggest an indirect percussion technique was used.
French researchers have conducted extensive blade-making experiments, and they have identified subtle attributes which vary systematically between blades struck by direct percussion, indirect percussion, and pressure. These are best evaluated with an assemblage of many specimens to evaluate rather than on individual artefacts in isolation.
Bipolar Percussion
In bipolar flaking, the core is braced on an anvil surface and a blow is struck onto the top, splitting it into sharp-edged flakes and fragments.
Bipolar cores are split by a crack initiated by the hammerstone or from the anvil support. Because the core is constrained from moving when struck, the flake is sometimes initiated by a process called ‘wedging’ which results in a flat fracture surface without a cone of force.
Most bipolar cores were struck many times, creating a large number of scars, some of them initiated by wedging and perhaps most initiated conchoidally. Bipolar cores are usually bidirectional, with flakes initiated from both ends of the core face.
Since the blows tend to be delivered near the middle of the platform, flakes may initiate down either side of the core. Also, the core can split into pieces that run its full length.
Both the platform struck with the hammerstone and the end supported by the anvil tend to become crushed, usually to both faces, and attrition often creates a U-shaped platform edge when viewed straight-on.
Bipolar cores were frequently rotated 90 degrees during reduction, establishing a new pair of platforms at right-angles to the first pair. The resulting core can be roughly rectangular in shape.
The bipolar core in this model displays most of the attributes described above—as you rotate the model see if you can find them.
The bipolar core in this model has a good example of a wedging initiation on one face.
Note the stacked undulations. This indicates considerable crack instability. This is common with wedging initiations and appears to be due to the high compressive force caused by the anvil support at the core's base.
Also take note of the flat profile of the scar. Since the flake initiates by wedging, it lacks a bulb of force. The crack initiates and travels straight down towards the anvil support without reorganising to travel down the core face (which is what creates a bulb of force).
Because propagation doesn't require manipulation of force relative to the core face, wedging initiations can be used to split thick stones, and stonemasons accomplish this using steel hammers to make paving blocks.
A second wedging-initiated flake propagated down the opposite side of the core from the same platform edge. The platform edge itself has broken away. The opposite platform edge is crushed with flakes initiated to both faces.
This bipolar core was made on a biface previously reduced by percussion and pressure flaking. The bifacial edge created by this is visible on one of the core's edges.
Pressure Flaking, Collateral
The pressure technique is similar to the indirect percussion technique in the way that the indentor can be placed very precisely on the platform to align with zones of high mass on the core face. The indentor can also be adjusted to subtly control the downward and outward forces that control the fracture path. However, in contrast to indirect percussion, force is applied using the body to load pressure onto the indentor until fracture occurs, rather than striking the end of it with a hammer.
Relative to the core edge, the flintknapper can angle the indentor up and down to adjust the length of the resulting flake, and side-to-side to adjust the angle of the flake scar relative to the platform edge. If the indentor is placed at right angles to the edge, the resulting flake scar will travel across the core at a right angle to the edge. This is referred to as 'collateral' flaking.
The biface in this model was made from milk glass in the recent past by a flintknapper in the Kimberley region of Western Australia. The Kimberley flintknappers were the last traditional group world-wide that practiced highly-skilled pressure flaking.
Note how most of the flake scars are oriented within about 70 to 90 degrees to the edge of the biface. This orientation results from the Kimberley pressure flaking technique, which involved supporting the far edge of the biface on an anvil when pressing off flakes. Variations in angle resulted from the orientation of the biface at the support point, but highly acute scar angles, as we will discuss later in the workshop, never occur on Kimberley points.
The holding technique also left the centre of the biface unconstrained (no compression was applied there), so the flakes tended to terminate at or near the biface's middle.
Note also the tiny serrations on the edge of the point. These were made in a flicking or sawing gesture, creating tiny flake scars that notched the point's edges.
The collateral flaking on this point is unpatterned. The flintknapper moved around the biface as necessary to remove flakes and contour the profile and cross section, as well as to provide a shape to the point. This 'selective' strategy is the most common approach to pressure flaking.
Now consider the masterpiece of pressure flaking in this model. Both of the faces are covered in a series of well-spaced collateral pressure flake scars. The scars are oriented at about 80 degrees to the biface edges (more on this later).
The pressure flaking was done in a regular order, progressing flake-by-flake from the base of the point moving towards the tip. This regularity is referred to as a 'serial' pressure flaking strategy, because the flakes are removed in a patterned series.
The ordering of the flake scars—the base-to-tip pattern—is reconstructed by looking at the way the flake scars overlap. In this case, the bottom edge of each pressure flake scar intrudes into the flake scar that appears spatially below it. Tiny run-on flakes ran into the preceding scar, ending in a jagged series of step terminations. These are best seen under magnification, and unfortunately the resolution of this model is insufficient to clearly capture such small attributes, but we will look at similar features later in this Workshop.
Another thing to consider is that each flake scars intrudes into the previous flake scar by about 1/3 in this case. When a pressure flake is detached, the crack initially expands outward from the point of force initiation in a V shape before the sides of the flake become more parallel. When part of a scar is removed by the next flake in the series, only the bottom part of the V remains. This illusion makes it appear as though the flakes are slightly angled—the 80 degree orientation—when in fact the flakes were probably removed very close to 90 degrees to the biface edge.
This same illusion was used by master flintknappers in Predynastic Egypt to make the famous Gertzian knives. By strategically spacing and ordering collateral serial pressure flake scars, the flintknappers achieved a wavy, S-shaped flake scar pattern across the face of the knife. This appearance is sometimes described as 'ripple flaking'.
Another masterful aspect of this point is the way the flintknapper made the pressure flakes terminate at or near the midline of the face, creating a ridge down the middle. The exact way this was achieved is unknown, but we know from fracture mechanics that it likely means the face of the stone was unrestricted. If the face was restricted in some way—by padding for example—the compression forces would have been maintained in the core face past the midline, and the flakes would have 'rolled over' the centre and run further, eliminating the midline ridge. With an unrestricted face, the compression forces were free to exit the core face at the midline, without a 'rolling over' effect. Modern flintknappers achieve this by removing pressure flakes over a hollow in the padding, using a support device such as a slotted block.
Pressure Flaking, Transverse-Parallel
Transverse-parallel pressure flaking scars travel across the biface at an oblique angle, generally between about 20 to 50 degrees relative to the edge of the point (where collateral pressure flaking scars are oriented at about 80 to 90 degrees).
In transverse-parallel pressure flaking, the angled scars from one edge are met near the middle of the biface by scars oriented at the reverse angle, pressed off the opposite edge. This gives the appearance of an angled line of pressure flake scars extending across the face of the biface.
There are two possible orientations to the flake scars. Picture transposing the letter Z over the biface, with the lower bar parallel to the base. A 'Z' pattern is when the flake scars are parallel to the middle part of the letter Z. Now picture transposing an S over the biface; an 'S' pattern is when the scars are parallel to the middle part of the S.
The point in this model shows a Z pattern. This is the least common pattern seen world-wide, although it is also found in Mesoamerica and Jomon period Japan.
Transverse-parallel flake scar patterning is undoubtedly attractive, but it also has a practical appeal. Recall that a pressure flake expands in a V shape from the point of force application. When a flake is removed at a right angle to the edge, both sides of the V are expressed on the flake scar. But when a flake is removed at an oblique angle to the edge, one side of the V is expressed, but there is no stone to support the other side of the V. Instead, the stone tears away the biface margin as it expands, leaving behind a razor-sharp edge. This is the sharpest edge that can be achieved on a bifacial-flaked tool.
The transverse-parallel pressure flaking on this model is only on one face of the point. It was mainly done as a resharpening technique on Elk River points.
The point in this model is one of the finest known examples of transverse-parallel pressure flaking from anywhere in the world.
The pressure flake scars are exceptionally small and uniform in size, displaying an S-shaped orientation.
Rotate the model to the unlabelled face and zoom into the flake scars from the right-hand edge. Note that the top edge of each flake scar is marked by a jagged series of run-on features. The edge of the flake scar flared out into the hollow of the preceding flake scar, and, finding insufficient mass to propagate under, the crack terminated in a jagged series of step terminations. This phenomenon is exceptionally useful for the lithic analyst, because it tells us that the jagged-edged scar came after the scar it intrudes into.
Note that, on this side of the point, the run-ons always intrude into the scar that is spatially on top. This tells us that the flintknapper started pressure-flaking this point at the tip and removed each flake, one after another, moving towards the base.
Each flake was flawlessly executed, attesting to remarkable rhythm and skill. Keep in mind also that the flintknapper needed to subtly adjust the inward force as they progressed, as the point became wider. It was a virtuoso performance, repeated on the opposite side, also progressing tip-to-base.
Now look at the smaller scars on the left-hand margin. Can you tell the flake removal order for those? Spoiler! : the flintknapper proceeded from the base of the point towards the tip, a pattern repeated on the left-hand edge on the opposite face. The longer flake scars from the right-hand edges intrude into the shorter, earlier flakes scars on the left-hand edges.
So, based on our analysis, we can say that the flintknapper first pressure-flaked up the left hand edge, base-to-tip, flipped the point and did this again on the left-hand edge; they then did a more invasive series of flake removals on the right-hand edge, tip-to-base, then flipped the point and repeated an invasive series of flake removals on the right-hand edge, again proceeding tip-to-base.
Note also that the basal thinning scars preceded all of this because the scars from the edges intrude into them. This may suggest that the flintknapper was resharpening this tool. The flake that removed the basal corner likely resulted from twisting in the haft when the tool was used.
What we have just completed is a 'diacritical' analysis of this point—reverse-engineeering the pressure-flaking process from the clues provided by the flake scars.
Now recall the discussion of collateral pressure flaking, and how that flintknapper made sure the pressure flakes terminated at or near the point's centreline (you may want to re-read that section). On this model, the flakes curl over the centreline, and many propagated nearly to the opposite edge. This suggests that the face of the point was supported in some way, which maintained the compressive forces. The result is a smooth lenticular cross section, as opposed to the prominent centreline seen in the collateral pressure-flaked point.
Pressure Flaking, Blades
In indirect percussion blade-making, the indentor can be placed very precisely on the platform to align with areas of high mass on the core face, and downward and outward forces can be subtly controlled by adjusting the angle of the punch.
The same is true for the placement of the indentor in pressure blade-making but force is applied using the body to load pressure onto the indentor until fracture occurs, rather than striking the end of it with a hammer.
Since the force is loaded onto the platform statically rather than dynamically, the resulting fracture path is exceptionally stable, with minimal undulations and side-to-side wandering. The resulting pressure blades are flat in profile with straight edges. The cores produced, with nearly identical flake-scars around the periphery, are often quite striking, and have been referred to as 'bullet cores'.
The flat profile, regular cross section, and straight edges made pressure blades ideal as hand-held knives or as cutting elements in composite tools, such as dart points, arrowheads, or hafted knives.
One of the difficult aspects of pressure blade manufacture is how to secure the blade core sufficiently rigidly that pressure blades can be pressed off. The force applied the platform to induce fracture, even on small cores, is very high, and the trick is to secure the core so it doesn't move away from the knapping tool when pressure is applied. The way this problem was solved is unknown, although modern experimenters have come up with holders and clamps in a number of different designs.
The obsidian core in this model is from Mesoamerica. Pressure blades were made in their millions by specialist flintknappers in Mesoamerica, and were an important part of the trade economy for the civilisations that arose there. Historical accounts indicate that these knappers sat on the ground and held the core between their feet, using a special lever-like tool to press off the blades.
Note how the platform is actually of smaller diameter than the central part of the core. This is because the pressure blades initiated conchoidally, and the bulb of force at the proximal end of the blade removed slightly more stone than the middle part of the blade. After scores of blade removals the platform angle becomes slightly obtuse, and removing further blades is no longer posssible.
As you rotate the core, observe the remarkably straight arrises (flake scar borders, and the uniform cross sections of the blade scars. These are hallmarks of the pressure blade-making technique.
An obsidian pressure blade from Mesoamerica can be viewed here and the distal end of a broken pressure blade from Pakistan can be viewed here. A small pressure blade core from Pakistan can be viewed here.
Now examine this blade core from Ohio. Do you think these blade scars were produced by pressure or direct percussion?
As you reflect on this, it might be useful to review this small blade core from France, which is a similar size to the Ohio core. These Mesolithic cores are thought to have been reduced by hard- and/or soft-hammer direct percussion. Note the relatively irregular shape of the blade scars.
Returning to the Ohio core, archaeologists have differing views on whether they were made by pressure or direct percussion, and it is difficult to evaluate based on one core in isolation--this core shows both irregular and regular flake scar margins, for instance. Archaeologists who have studied whole assemblages of these Ohio cores think they were likely produced by direct percussion with a soft hammer.
Pecking
Pecking, or hammer dressing, involves shaping a stone by attrition rather than by flaking. It tended to be used on stones that are difficult or impossible to flake.
The technique involves striking the face of the stone repeatedly, and each blow pulverises a tiny amount of the surface, which turns to powder under the impact. Eventually the attrition caused by thousands of blows incrementally reduces the stone into the desired shape.
The sizes of the peck-marks depends on the hardness of the stone being pecked combined with the strength of the pecking blow. Too hard a blow can break the stone being shaped.
The Australian axe in this model was made on a beach or river cobble, and the small roughly circular pecking pits can be readily differentiated from the cobble cortex.
Rotate the model to an edge-on view to see how pecking was used to reduce the end of the axe to an acute edge for sharpening by grinding. The groove for the handle was also made by pecking.
Flaking was often combined with pecking to manufacture axes, or rework them when they were broken. Examples of Australian axes that are both flaked and pecked can be viewed here and here. Pecking was a useful technique to reduce the thickness of a stone axe shaped by percussion flaking.
Pecking was also used to manufacture other objects. For instance, the outside surface of this North American soapstone bowl was partly shaped by pecking, as was this Australian seed grinding dish.
If pecking was concentrated in one spot for long enough (usually on opposite sides), a hole could be made through an object. This club head from New Guinea was shaped and perforated using a pecking technique.
Pecking was also used as a resharpening technique. When grinding dishes and top stones lost much of their abrasiveness due to use-wear, Aboriginal people in Australia would peck the surface. This helped restore a grinding stone's abrasiveness.
Peck marks are clearly visible on both surfaces of this model of a top stone (called a 'muller' in Australia).
Grinding
Grinding was a common way of finishing certain types of stone objects for use, often after they were initially shaped by flaking and pecking.
Grinding was an especially popular method for preparing the cutting edges on stone axes, a technique that first appeared in Australia by at least 40,000 years ago and was independently invented in many other regions in later prehistory. Edge-ground 'polished' axes are considered characteristic tools of the Neolithic period in Europe, and people in New Guinea make edge-ground axes today.
This model is of a large 'prestige' axe from Neolithic France. The long striations visible on the faces of this axe, particularly noticeable on the axe's sides, were created by the process of grinding down the axe into this shape.
Axe-grinding created grooves in the sandstone bedrock where the process was often undertaken. This model is of a boulder used during the Neolithic in France to grind axes.
Grinding can be a long process, particularly with hard materials like flint. This flint axe was only ground on the faces rather than the sides, which is typical for tools of this type.
Grinding was also used to finish objects with complex shapes, such as the ornate axes that can be viewed here and here. Tools and objects with ornate shapes were likely made by a combination of pecking and grinding.
By ca. 5500 BP, exceptionally hard stones, such as chalcedony, jade, and quartz crystal, were ground into objects. These objects included axes, sculptures, beads, and decorated seals and gems. The secret to this process—attested in early Sumerian and Greek texts, and documented by archaeological analysis—involves the use of carborundum grit made from the same minerals that form ruby and sapphire. These minerals are only second in hardness to diamond, and they create distinctive scratches which can be identified using electron microscopes.
Sawing
In the modern masonry industry, motor-driven saw blades with embedded industrial diamond are used to to cut rock into slabs and blocks. The same practice was done by hand by Maori people in New Zealand, where jade and jadeite, known as pounamu, was cut into sections using thin pieces of sandstone as saws. Adzes, clubs, and other objects were then shaped by grinding.
Rotate the adze in this model to see a raised ridge on one of the sides. This was created by first sawing from opposite faces of the jadeite slab until the cuts were relatively close together, and then snapping off the piece between the saw grooves.
Now rotate the adze to view the face just back from the bevelled cutting edge. A shallow but narrow groove is visible there. This is probably a remnant saw-cut from early in the reduction process.
The groove is exceptionally narrow, and sandstone saws tend to leave wider saw cuts. In the middle 1900s and perhaps earlier, wire was used with abrasives to cut through the jade, and it is likely that this groove was created using wire. If so, the adze dates to the relatively recent past.
Modern lapidary equipment is used today to make jade objects, and these saws are capable of cutting completely through the jade. Hence the saw-and-snap technique is rarely practiced by modern jade workers in New Zealand.
Sawing was likely used in other jade-working technologies, particularly in China, where jade industries flourished for thousands of years.