Lithic reduction

Percussion reduction, or percussion flaking, refers to removal of flakes by impact. Generally, a core or other objective piece, such as a partially formed tool, is held in one hand, and struck with a hammer or percussor. Alternatively, the objective piece can also be struck between a stationary anvil-stone, known as bipolar percussion. Percussion can also be done by throwing the objective piece at an anvil stone. This is sometimes called projectile percussion. Percussors are traditionally either a stone cobble or pebble, often referred to as a hammerstone, or a billet made of bone, antler, or wood.[7] Often, flakes are struck from a core using a punch, in which case the percussor never actually makes contact with the objective piece. This technique is referred to as indirect percussion.[8]

An example of hard hammer percussion.

Projectile percussion is so basic as to not be considered a technique. It involves throwing the toolstone at a stationary anvil stone. This method provides virtually no control over how the toolstone will fragment, and therefore produces a great deal of shatter, and few flakes. It is difficult to be sure whether or not this method of lithic reduction was ever a commonplace practice, although noting sharp edges on a broken rock might have led early humans to first recognize the value of lithic reduction.

In bipolar percussion the objective piece of toolstone is placed on an anvil stone, and then the percussion force is applied to the tool stone.[9] Like projectile percussion, the tool stone is likely to shatter, rather than producing a single flake. Unlike projectile percussion, the technique has some degree of control to it. Bipolar percussion is not popular with hobbyists, but there is evidence that bipolar percussion was the preferred way of dealing with certain problems. Bipolar percussion has the benefit of producing many sharp flakes, and triangular pieces of stone which can be useful as drills. Bipolar percussion also does not require the manufacturer to locate a platform before setting to work, and bipolar percussion can produce sharp flakes almost the size of the original piece of tool stone. The lack of control makes bipolar percussion undesirable in many situations, but the benefits mean that it often has a use, especially if workable material is rare. Bipolar percussion is often used to break open small cobbles, or to have a second chance with spent lithic cores, broken bifaces, and tools that have been reworked so much that it is impossible to make further useful tools using traditional lithic reduction. The end result of bipolar percussion is often a big mess, with only a few pieces that can be useful as cores or flakes for further working, but if other methods would result in a total dead-end, bipolar percussion may be desirable.

This image is an example of an obsidian core that has had flakes removed using bipolar percussion.

An alternative view of the bipolar reduction technique is offered by Jan Willem Van der Drift which contradicts the suggestion that there is little control over fracturing. The characteristics of bipolar reduction are different from that occurring in conchoidal fracture and are therefore often misinterpreted by archaeologists and lithic experts.

Hard hammer techniques are generally used to remove large flakes of stone. Early flintknappers and hobbyists replicating their methods often use cobbles of very hard stone, such as quartzite. This technique can be used by flintknappers to remove broad flakes that can be made into smaller tools. This method of manufacture is believed to have been used to make some of the earliest stone tools ever found, some of which date from over 2 million years ago.[10]

It is the use of hard-hammer percussion that most often results in the formation of the typical features of conchoidal fracture on the detached flake, such as the bulb of percussion and compression rings.[11]

An example of soft hammer percussion

Soft-hammer percussion involves the use of a billet, usually made of wood, bone or antler as the percussor. These softer materials are easier to shape than stone hammers, and therefore can be made into more precise tools. Soft hammers also deform around the sharp edges of worked stone, rather than shattering through them, making it desirable for working tool stone that already has been worked to some degree before. Soft hammers of course also do not have as much force behind them as hard hammers do. Flakes produced by soft hammers are generally smaller and thinner than those produced by hard-hammer flaking; thus, soft-hammer flaking is often used after hard-hammer flaking in a lithic reduction sequence to do finer work.[12] As well as this, soft-hammers can produce longer flakes which aid in the conservation of materials because they produce a longer cutting edge per unit of mass lost.[13]

In most cases, the amount of pressure applied to the objective piece in soft-hammer percussion is not enough for the formation of a typical conchoidal fracture. Rather, soft-hammer flakes are most often produced by what is referred to as a bending fracture, so-called because the flake is quite literally bent or "peeled" from the objective piece. A bending fracture can be produced with a hard hammer.[14] Flakes removed in this manner lack a bulb of percussion, and are distinguished instead by the presence of a small lip where the flake's striking platform has separated from the objective piece.[15]

Indirect percussion involves the use of a punch and hammer. The punch and hammer make it possible to apply large force to very small areas of a stone tool. Indirect percussion is therefore often used to achieve detail work on smaller tools. Some modern hobbyists make use of indirect percussion almost exclusively, with little or no pressure flaking to finish their work.

Since indirect percussion can be so precisely placed, the platform is often much smaller on flakes produced in this way than in other methods of flake removal. Of course, indirect percussion requires two hands to hold the percussing tool set. One holds the hammer, and one holds the punch. Therefore, modern hobbyists must use a third object in order to hold the targeted piece of tool stone while they strike it. Often, some sort of clamp or vise is used. No evidence for such devices has yet been found in the archaeological record, but this is partly because they would normally be made of perishable materials, and partly because they can have great variation in design.

An example of pressure flaking

Pressure flaking is a method of trimming the edge of a stone tool by removing small lithic flakes by pressing on the stone with a sharp instrument rather than striking it with a percussor. This method, which often uses punches made from bone or antler tines (or, among modern hobbyists, copper punches or even nails), provides a greater means of controlling the direction and quantity of the applied force than when using even the most careful percussive flaking. Copper retoucheurs to facilitate this process were widely employed in the Early Bronze Age – and may therefore be associated with Beaker Culture in northwestern Europe.

Usually, the objective piece is held clasped in the flintknapper's hand, with a durable piece of fabric or leather protecting the flintknapper's palm from the sharpness of the flakes removed. The tip of the flaking tool is placed against the edge of the stone tool and pressed hard, removing a small linear or lunate flake from the opposite side. The process also involves frequent preparation of the edge to form better platforms for pressing off flakes. This is usually accomplished with abraiders made from a coarse-grained stone such as basalt or quartzite. Great care must be taken during pressure flaking so that perverse fractures that break the entire tool do not occur. Occasionally, outrepasse breaks occur when the force propagates across and through the tool in such a way that the entire opposite margin is removed.[16]

The use of pressure flaking facilitated the early production of sharper and more finely detailed tools. Pressure flaking also gave toolmakers the ability to create notches where the objective piece could be bound more securely to the shaft of the weapon or tool and increasing the object's utility.

An archaeological discovery in 2010 in Blombos Cave, South Africa, places the use of pressure flaking by early humans to make stone tools back to 73,000 BCE, 55,000 years earlier than previously accepted. The previously accepted date, "no more than 20,000 years ago",[17] was based upon the earliest evidence previously available, which derived from findings of the Upper Paleolithic Solutrean culture in France and Spain.[18]