Summary
Highlights
In 1620, Cornelius Drebbel chilled the largest hall in England, Westminster Abbey, so effectively that King James I was forced to leave to get warm. This event is considered the first air conditioner, utilizing a white crystal that gets cold when it touches water. This technology, which worked without any power source or machine, mysteriously vanished.
The crystal responsible for this cooling effect is saltpeter, also known as potassium nitrate. When dissolved in water, saltpeter undergoes an endothermic reaction, absorbing heat from its surroundings and dramatically lowering the water's temperature to near freezing. This same chemical process is used in modern instant cold packs.
Before Drebbel, an Italian polymath, Giambattista della Porta, documented saltpeter's cooling properties around 1558. This knowledge spread throughout Europe, with wealthy individuals using saltpeter to chill drinks. Drebbel's innovation was in scaling this tabletop effect to cool an entire large room, proving its potential for widespread use.
For over a century, saltpeter cooling was the only method available for artificial deep cold. However, the exact same crystal was also the primary component of gunpowder, making up about 75% of its weight. Humanity faced a choice between using saltpeter for comfort or for firepower.
Due to constant warfare in the 17th and 18th centuries, saltpeter became an incredibly strategic material, comparable to modern oil or uranium. Nations, particularly Britain, hoarded it, especially after gaining control of the abundant supplies in Bengal, India, by 1757. This made it virtually impossible to develop saltpeter cooling for domestic use.
Saltpeter cooling was ultimately supplanted by a different approach to refrigeration. In 1748, William Cullen demonstrated cooling through the evaporation of liquid under a vacuum, a principle that forms the basis of modern refrigerators and air conditioners. This new method gained traction because it could be commercialized, patented, manufactured, and sold as a product, unlike the readily available and unpatentable saltpeter method.
While saltpeter cooling had limitations, it was a legitimate path to low-power cooling that was abandoned not due to its ineffectiveness, but because its raw material was claimed for war and later overshadowed by more profitable, proprietary technologies. This historical pattern of simple, effective methods being buried by strategic and commercial interests is a recurring theme in the history of home comfort.