The Problem Behind the Spark
People could use naturally occurring fire long before they could necessarily produce it themselves. A burning branch could be carried away, and embers could be kept alive for later use. Making a fresh fire whenever it was needed presented a different problem. Even that achievement involved several stages: generating heat, catching it in a receptive material and transferring it to larger fuel. Histories of fire-making sometimes treat these stages as a single discovery, although success at one did not guarantee success at the others.
The beginnings of deliberate ignition remain uncertain. A convincing explanation of how a technique could have arisen is not evidence that it actually arose in that way. Heat generated during woodworking and sparks observed during stoneworking both offer plausible starting points. Neither identifies a discoverer or establishes a universal sequence. The scattered distribution of related techniques also permits more than one explanation: knowledge may have travelled between communities, or similar problems may have prompted independent solutions. Consequently, a neat sequence of inventions may tell us less about the past than its apparent certainty suggests.
Equally misleading is the assumption that carrying fire proves an inability to make it. Keeping a glowing brand could spare its owner the labour of starting again, even where the necessary skill was available. An observer might mistake a practical saving of time for a lack of knowledge. In one case, the aim was to preserve what was already available; in the other, it was to stop relying on an earlier fire remaining alive. A community could pursue both aims. Learning to make fire did not remove the value of keeping it.
Much depended on what happened between the first trace of heat and the burning of substantial fuel. A visible spark could be spectacular but practically useless if nothing caught it. Conversely, an inconspicuous ember could become the foundation of a cooking fire. Tinder performed the connecting role: it received heat too brief or too concentrated in one spot to ignite the main fuel directly. The preparation of this receptive material was consequently as important as the apparent ingenuity of the device. Judging performance solely by the production of sparks overlooks the stage at which many attempts fail.
Wooden apparatus presented a further complication. Water held in the wood absorbed some of the heat as the material warmed and dried, while the choice of wood and the operator's movements affected the production and accumulation of heated particles. Friction describes the source of heat, but not one uniform procedure. A hand drill concentrated rotation at a relatively fixed point; a fire plough carried its working end along a groove. Both required suitable contact between wooden surfaces, although the location at which the work was performed differed. Increasing effort without correcting unsuitable materials could merely prolong failure.
The hand drill also demanded an awkward combination of downward pressure and continued rotation. The palms supplied the turning movement but repeatedly descended along the shaft, requiring the operator to recover position. A bow drill transferred rotation to a cord, enabling the turning action to be maintained without this repeated repositioning. The operator could manage the movement more easily, although heat was still produced in the same way. A support at the upper end kept the shaft under pressure, but resistance there was undesirable: heat needed at the lower contact point could otherwise be accompanied by wasted work at the top. More components improved control while creating additional opportunities for poor adjustment.
Striking arrangements altered both the working materials and the character of the ignition source. Flint used with iron pyrite could produce sparks without a manufactured metal striker. In the flint-and-steel arrangement, by contrast, the hard stone detached minute particles from the steel, a manufactured iron alloy; these heated particles supplied the ignition source. It was therefore misleading to describe the stone itself as burning. The stone's importance lay in its action on its partner. Neither arrangement eliminated the need for carefully prepared tinder, and the durability of the striking equipment should not be confused with the reliability of the complete operation.
Another device, the fire piston, made confinement essential for a quite different reason. A small quantity of tinder was carried into a cylinder by a closely fitting piston. A rapid reduction in the volume available to trapped air raised its temperature sufficiently to ignite suitable tinder. This was compression rather than the rubbing of two fuel surfaces. Leakage defeated the principle: an opening that released the air prevented the required conditions from developing. Yet an airtight enclosure was not beneficial to every stage of fire-making. A glowing material subsequently needed access to air to continue burning. The same feature could thus assist ignition in one apparatus and obstruct combustion in another context.
A burning glass avoided the physical effort of drilling or striking by concentrating solar energy. Its convenience depended on conditions the operator could not control. Cloud could interrupt performance without damaging any component, and darkness could remove the energy supply altogether. The issue was not whether the apparatus remained intact, but whether its surroundings continued to provide what it required. Portability alone was therefore an inadequate measure of usefulness: a light, readily carried device might still be less dependable than heavier equipment under particular conditions.
Safety matches illustrate a different response to reliability. Ease of ignition had to be balanced against the possibility of ignition at an unwanted moment. The solution did not simply remove all reactive substances. Instead, important ingredients were distributed between the match head and a specially prepared striking surface. Red phosphorus was placed on the latter, while the head contained an oxidising component. Keeping these ingredients apart limited the circumstances in which ignition could occur. The striking action brought the arrangement into use; the improved design depended on the relationship between components, not on the disappearance of combustible material. Across these techniques, progress meant controlling the conditions of ignition as much as increasing the ability to generate heat.