Making stone tools starts with selecting the right rock and learning three core techniques: hard hammer percussion, soft hammer percussion, and pressure flaking. These are the same methods humans have used for over two million years, and they remain the foundation of modern flintknapping. With the right materials, some patience, and proper safety gear, you can produce everything from simple cutting flakes to finely shaped arrowheads.
Choosing the Right Stone
Not every rock will work. The key property you need is called conchoidal fracture, which means the stone breaks in smooth, curved waves rather than crumbling or splitting along flat planes. This type of fracture produces the sharp edges that make stone tools useful. Stones that fracture this way share a common trait: high silica content and a fine-grained or glassy internal structure with minimal crystal growth.
The best materials for beginners are flint, chert, and obsidian. Flint rates a 7 on the Mohs hardness scale, has a glassy luster, and flakes with relatively limited effort. Chert is closely related to flint and widely available across North America. Obsidian is natural volcanic glass with a silica content over 70%, formed when fast-moving lava cooled too quickly for crystals to develop. It produces the sharpest edges of any stone tool material, but it’s also brittle and less forgiving of mistakes.
Other workable stones include jasper, agate, quartz in its pure crystalline form, and various silicified mudstones. Jasper’s high silica content gives it a reliable conchoidal fracture. Agate fractures well too, though it often benefits from heat treatment before knapping. If you’re just starting out, look for river cobbles of flint or chert. Glass bottle bottoms also work as inexpensive practice material to learn the mechanics before investing in good stone.
Heat Treatment for Better Workability
Some stones become significantly easier to flake after controlled heating. Heat treatment changes the internal structure of the stone, giving it a waxy luster and allowing flakes to travel farther with less force. This is especially useful for materials like novaculite, certain cherts, and agate that feel “grainy” or resist clean flaking in their natural state.
The process requires patience. Research from the Arkansas Archeological Survey outlines a procedure that begins with a drying phase: raising the temperature slowly, at about 20°C per hour, to 175°C and holding it there for 8 hours to drive out moisture. After drying, the temperature continues rising at the same gradual rate until reaching the target temperature, typically somewhere between 300°C and 750°C depending on the material. The stone is then held at that peak temperature for around 12 hours before the heat source is turned off and the stone cools naturally to room temperature. Rushing any stage risks thermal shock, which can shatter the piece. A basic ceramic kiln works well for this. Campfire heating is possible but much harder to control.
Tools You Need
You don’t need much equipment, but each tool serves a distinct purpose:
- Hammerstone: A hard, rounded river cobble (granite or quartzite) roughly fist-sized. This is your primary tool for the initial shaping stages.
- Billet: A cylinder of antler, hardwood, or copper used for soft hammer percussion. Antler tines from deer or elk are traditional and widely available.
- Pressure flaker: A pointed tool made from bone, antler, or copper wire set in a handle. This is used for the final shaping and edge refinement.
- Abrader: A piece of sandstone or similar rough stone used to prepare striking platforms. This is a small but critical tool.
- Leather pad: A thick piece of leather to protect your leg while holding the workpiece. Stone fragments are razor-sharp.
Safety glasses are not optional. Small flakes can fly unpredictably, and obsidian in particular produces fragments sharper than surgical steel. Leather gloves, long pants, and closed shoes protect against the debris that accumulates quickly in your work area.
Hard Hammer Percussion: Rough Shaping
Hard hammer percussion is the oldest and most fundamental technique. You hold the raw stone (called a core) in your non-dominant hand, resting it on the leather pad on your thigh, and strike it near the edge with a hammerstone. The goal is to remove large flakes and establish the general shape of your tool.
Angle matters more than force. Strike at roughly 45 degrees to the platform (the flat surface you’re hitting). If you strike too steeply, the flake will be short and thick or the stone will simply crush at the point of impact. If the angle is too shallow, the hammer will skip off the surface. The force of the blow should travel into and across the stone, not straight down into it.
Each strike removes a flake and creates a new surface geometry that determines where the next flake can come from. This is the core challenge of flintknapping: every removal changes the shape, and you need to think several steps ahead. Start by working around the perimeter of the core, removing flakes to create a rough biface, a piece thinned from both sides with a lens-shaped cross-section.
Soft Hammer Percussion: Thinning and Shaping
Once you have a rough biface, switch to a soft hammer, typically an antler billet. Soft hammer strikes produce longer, thinner, flatter flakes than a hammerstone. The flakes tend to have smaller, less pronounced bulbs at the point of impact and travel farther across the surface of the tool. This lets you thin the biface without breaking it and begin refining the overall shape.
The technique is similar to hard hammer work but requires more precision. You’re now aiming for specific spots on the edge, and the contact between the billet and the stone is slightly different. The softer material grips the platform edge briefly before the flake releases, which is why the resulting flakes are thinner and more controlled. Hold the biface so the platform edge you want to strike slightly overhangs your supporting hand or leg pad, and swing the billet in a smooth arc that follows through the strike.
Platform Preparation
Before each strike during the thinning stage, you need to prepare the platform. This is where the abrader comes in. By sanding the edge of the stone where you plan to strike, you remove thin, weak portions that would simply crumble under impact. A properly abraded platform is slightly rounded and sturdy enough to absorb the force of the blow and transfer it into a clean flake. Skipping this step is one of the most common reasons beginners shatter their workpieces. Abrading the platform produces longer flakes and dramatically reduces shatter.
You should also pay attention to the angle between the platform and the face of the tool. If the edge is too acute (too thin), it will crush. If it’s too obtuse (too steep), flakes will dive into the body of the tool and create thick, stubby removals. The ideal is a platform that’s slightly less than 90 degrees relative to the surface you want the flake to travel across.
Pressure Flaking: Final Refinement
Pressure flaking is the finishing technique. Instead of striking the stone, you place the tip of a pointed tool (bone, antler, or copper) directly against the edge and push. You start by pressing into the edge, then shift the direction of force downward, snapping off a small, controlled flake. This lets you shape delicate features, straighten an uneven edge, sharpen a dulled one, and create the characteristic notches on arrowheads where they attach to a shaft.
The workpiece sits on the leather pad on your palm or thigh, with the edge you’re working on facing up and slightly toward you. Place the pressure flaker’s tip a few millimeters back from the very edge. If you push right at the edge, you’ll just crush it. Setting back slightly gives the flake room to initiate and peel off cleanly. The flakes removed this way are tiny compared to percussion flakes, sometimes only a few millimeters long, but the cumulative effect transforms a rough edge into something genuinely sharp.
This is the technique that separates a crude chopping tool from a finished projectile point. It requires the most practice but gives you the most control. Expect to break several pieces before the motion becomes intuitive.
Making a Simple Flake Tool
The easiest project for a beginner is not a shaped tool at all. It’s a simple flake. For over a million years, the primary stone tool was just a sharp flake struck from a core. To make one, find a fist-sized cobble of flint or chert, identify a natural platform (any relatively flat surface near an edge), and strike it with your hammerstone at the correct angle. The flake that comes off has a naturally sharp edge that can cut hide, slice meat, or scrape wood. The Oldowan toolkit, humanity’s first stone tool tradition, was built almost entirely on this principle.
Once you’re comfortable producing predictable flakes, try shaping a simple biface. Start with a flat, oval cobble or a large thick flake. Work around the edges with your hammerstone to establish a rough shape, switch to a billet to thin it, and finish the edges with pressure flaking. A palm-sized oval biface, similar to what archaeologists call a handaxe, is a satisfying first shaped project and teaches every fundamental skill in sequence.
Common Mistakes and How to Avoid Them
Most beginners hit too hard and aim too imprecisely. Flintknapping is about placement and angle, not brute strength. A well-placed moderate strike removes a better flake than a powerful misplaced one. Other frequent problems include failing to abrade platforms, trying to remove flakes from edges that are too thin or too steep, and not rotating the piece often enough. You should flip and turn your biface constantly, working alternating sides to keep it symmetrical and maintain usable platform angles.
Thickness is the enemy. If your biface gets too thick relative to its width, it becomes nearly impossible to thin without breaking. The solution is to focus on thinning early and often, before the piece gets too small. If you find yourself with a chunky piece and no good platforms, you can try to set up a new platform by removing a flake from the opposite side, creating a fresh angle to work from.
Learning from video is far more effective than text alone for this skill. The motion, angle, and force of each strike are easier to understand when watched in real time. Many experienced knappers post detailed tutorials online, and local flintknapping groups exist in most regions where suitable stone is available.