Spermaceti: the sperm whale head wax that defined the unit of light

For more than a century, the official unit of luminous intensity in the English-speaking world was defined by a candle. Not just any candle: a spermaceti candle, the wax drawn from the head of the sperm whale, burning at a fixed rate. Candlepower literally measured light in sperm whales.

An organ that makes up 40% of the animal

The sperm whale’s head is not a skull. It is an acoustic device. It contains the spermaceti organ, a vast sac of liquid wax that can hold about 1,900 litres, and the head complex extends over nearly 40% of the body length. In a large male of eighteen metres, that amounts to several tonnes.

Its function is to focus the most powerful echolocation clicks in the animal kingdom, and probably to play a part in the control of buoyancy during dives. Our page on the spermaceti organ sets out how this works.

Chemically, it is not an ordinary fat but a mixture of wax esters and triglycerides, liquid and clear in the living animal, which sets into a white, crystalline mass as it cools. Hence its French name, blanc de baleine, whale white, and a lasting misapprehension among whalers, who took the substance for sperm.

The best candle ever made

A tallow candle smokes, drips and smells of fat. A beeswax candle is expensive. Spermaceti offered both advantages without the drawbacks: a bright, steady and odourless flame, a hard wax that does not slump, and slow burning.

Its consistency was such that it came to be used as a standard. Candlepower, defined in the nineteenth century from a spermaceti candle of a given weight burning at a given rate, remained the reference unit until it was replaced by the candela in the twentieth century.

The oil that neither freezes nor thickens

The second use survived far longer than lighting, and it explains why the sperm whale was hunted into the 1970s.

Sperm whale oil has properties that the petroleum lubricants of the time could not match: it keeps a stable viscosity over a very wide range of temperatures, does not break down easily, does not absorb water and clings to metal. It was therefore used wherever a failure is expensive: clockmaking, sewing machines, precision instruments, firearms, and even automatic car gearboxes.

It also went into cosmetics, creams and ointments, where its texture was sought after.

1972: the ban, and what followed

In 1972 the United States adopted the Marine Mammal Protection Act, which protects the sperm whale and closed the American market to its products. As the country was the leading consumer of precision lubricants, the effect was immediate.

Industry then turned to two substitutes, jojoba oil, from a desert shrub whose seeds produce very similar wax esters, and synthetic esters. The first was no chance discovery: its chemical composition resembles that of spermaceti far more than that of an ordinary vegetable oil.

A useful clarification, since the confusion persists: in cosmetic ingredient lists today, the word spermaceti denotes a synthetic or plant-derived product. The sperm whale is protected under CITES and international trade in its products is prohibited.

The cost to the species

The sperm whale is the most heavily hunted species of the twentieth century: more than 760,000 individuals killed according to the statistics compiled by the International Whaling Commission. The global population fell by about 70%.

Hunting also targeted large males preferentially, as they carry the most spermaceti. Yet these are the breeding animals. Selective pressure on that age class continues to affect demography long after catches stop, as our page on the history of whaling sets out.

This page is part of our feature on whale products, which presents the six main uses that drove commercial whaling.