As if it wasn't enough that the sperm whale, Physeter macrocephalus, was cursed with a cruelly descriptive name that translates directly as 'bigheaded blower', beginning in the late 18th century it was doomed to have its oversized head - about a third of its body - hacked open to get to the cavities and hollows within. Why? At that time the whaling industry began to take off and whalers discovered its head harboured a fatty tissue which turned out to be most useful, not to mention rather lucrative. This white and waxy substance, called spermaceti, was used making candles, ointments and cosmetics, and since the whalers were going to slit open the whale for the ambergris in its intestines and the blubber beneath its skin, they were only too happy to collect the spermaceti as well.
Spermaceti's scientific composition is basically ethereal salts of palmitic acid with ethal and a few other hydrocarbon bases. It is insoluble in water and doesn't putrefy. It is clear, therefore, why it was so popular for lubricating leather bindings, waterproofing oilskins, making candles and so on. In fact, it practically revolutionised candlemaking at the time - it didn't smell when burnt, it was harder than tallow or beeswax and it didn't soften or bend at the heights of summer. At one point, spermaceti would be mixed with sugar and used to dose children with coughs, colds and catarrh. (It would seem pretty much anything's worth a try when you've got a child indiscriminately hawking up phlegm, even feeding them the contents of a whale's head.) It also lends itself to the creation of a soft crayon which can be used to write on clean glass.
After using hot water to extract it from the whale's head the spermaceti was usually brought back to shore in barrels, where it would have had plenty of time to separate out. A preliminary pressing would remove some of the sperm oil, and the wax could be remelted and washed with a weak solution of carbonate or other caustic alkali before casting it into moulds. These blocks could then be cut up and sold commercially. Refined spermaceti is sometimes called cetin.
Thankfully for the sperm whales, a substitute formed from tallow and coconut oil was developed in the 1980s, so the more civilised amongst us tend to leave the poor beasts alone now.