Direct Percussion Flaking

Direct percussion flaking involves striking the core platform with a hammer (or ‘indentor’) to detach the flake. Forceful blows are called ‘percussion’ to differentiate the technique from ‘pressure’, which involved pressing the flakes from the core.

The direct percussion technique was practiced in all times and places and almost all toolmaking methods used percussion flaking at some point in the reduction sequence. The history of human technology began with flaking and some researchers have suggested that the evolution of the human hand and arm was driven in part by the need to percussion-flake stone into tools.

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Hard-Hammer, Core Reduction

In hard-hammer percussion, the indentor was a stone made from resistant material such as igneous, volcanic, or metamorphic materials. Water-worn cobbles were frequently chosen for hammerstones because of their convenient shape. The hard-hammer blow was delivered back from the core edge rather than directly on the edge. This was done partly to prevent the fragile core edge from shattering, but also as a way to adjust the size of the resulting flake: generally, the farther back from the edge the stoneworker initiated the flake, the larger the flake would be.

In ‘freehand’ core reduction, the core was held in the non-dominant hand, and the dominant hand swung the hammer. Freehand percussion was the most common stone-flaking technique observed among traditional stone-using people in the historical period.

Large cores that were too heavy to hold in the hand were rested on the ground for flaking. Huge cores—a metre or more in size—were reduced by throwing a large hammer onto the platform, which could produce enormous flakes as blanks for reducing into large tools like axes. Alternatively, the core itself was thrown down onto a bedrock surface in the hope that it would split and produce chunks suitable for freehand percussion flaking.

Single Platform Core

Oldowan Core

Levallois Core

Flake

Core on Flake

Bifacial Core

Bidirectional Core

Hard-Hammer, Shaping

Other tools—including many types of bifacial knives and points—were shaped in their initial stages using a hard hammerstone, and by other techniques in the later stages. Hard-hammer percussion contoured the blank and set it up for soft hammer percussion or pressure flaking.

Similarly, hard-hammer direct percussion flaking was used to establish the core morphology necessary for sophisticated blade-making methods using soft hammers, punches, or special pressure-flaking tools.

Stone Axe Blank

Stone Adze

Pebble-Edged Core

Handaxe

Hard-Hammer, Retouching and Resharpening

As the tool was used, the edge of a retouched flake would become dull or clogged by the material being worked, and further retouching was done to resharpen the edge. Retouching and resharpening was frequently done with a small hammerstone.

‘Backing’ was a hard-hammer technique that involved resting the flake on a surface and trimming the edge with a hammerstone. This steepened the edge opposite a sharp edge, creating a ‘back’ that could be set in glue or resin, or held in the hand without cutting the finger.

Retouched Flake

Macroblade Point

Flake Chopper

Hard-Hammer Blade-making

Naviform Blade Core

Microblade Core

Macroblade Point

Macroblade Point

Macroblade Point

Macroblade Core on Flake

Macroblade Core

Macroblade Core

Blade

Bipolar Flaking

The bipolar technique was frequently used on small pebbles or to recycle discarded flakes and tools into additional usable flakes. Bipolar flaking was invented in Africa at least 2.5 million years ago and has been practiced continuously ever since, in all times and places and into the recent past.

Bipolar percussion created flat wedging initiations that lack a well-defined bulb of force, with crushing at the platform and anvil-supported ends. Because of this, it can be difficult to determine which products of bipolar flaking are the flakes and which are the cores. Many archaeologists avoid this problem by calling them ‘bipolar artefacts’.

Bipolar Core

Truncating

The flat truncation faces could also be used as platforms for striking off additional small flakes by direct percussion. In some technologies, the truncation technique was used to produced blanks of a certain shape or regular size.

For instance, in the recent past flintknappers in England truncated blades into square pieces for use in flintlock firearms. Homo floresiensis used truncation as one technique to reduce cores, and Native Americans sometimes truncated thin bifaces into pie-shaped pieces for use as tools. The truncation technique was sometimes used to ritually ‘kill’ stone tools before interring them in ceremonial caches or burials.

Gunflint

Soft-Hammer, Thinning and Resharpening

Thinning was accomplished by taking more off the centre of the biface than was lost from the edges from attrition as the platforms were removed. This required striking the thinning flakes so they travelled past the centreline of the biface from small platforms on the biface edge. Since soft hammers allowed the stoneworker to strike right on the very edge of the biface, rather than in from the edge, they were the ideal tool for this.

Stoneworkers were able to use soft hammer percussion to make very thin bifacial blanks for knives, daggers, and armatures for spears and darts. Soft hammers were also used to flake the edges of tools to resharpen them. Small bone ‘retouchers’ are frequently recovered from Pleistocene sites in Europe, and in the recent past Aboriginal people in parts of Australia used wood boomerangs to resharpen flaked-stone adzes.