As we transition from spring to summer, it's interesting to reflect on the role of cork in the advancement of food preservation and storage. The earliest food preservation methods involved cave and pit storage, leveraging cooler underground temperatures to extend the lifespan of fruits, vegetables, and meats. Over time, ice was incorporated into these storage systems, further lowering the temperature. One notable example is the ice pit at the Jamestown settlement. However, it wasn't until the 19th century that technological progress led to an invention that laid the foundation for a common household appliance we rely on today.
The first icebox was created by Thomas Moore in 1802, who was later granted a patent by Thomas Jefferson himself. This early cooler allowed him to transport butter to market in the dog days of summer without it melting. This began a flurry of innovation and activity to learn about the most insulating and practical materials to fill the ice chests and boxes.
An illustrated drawing showing a vintage ice box with nots on how they worked.
From its humble beginnings in 1806 in Boston, the ice trade quickly expanded to international markets. Insulated shipping compartments and ships were used to transport ice, a technological marvel of the time. This booming business during the winter months not only allowed for the enjoyment of cooled beverages but also extended preservation times, reaching places that previously could only dream of ice. The south of Spain, parts of Africa, and eventually even the tropical climates of Southeast Asia were all able to benefit from this technological advancement in food preservation.
Throughout the 19th and early 20th century, ice was a big business. Families would have an ice delivery from the ice man much as they did the milkman, allowing them to store milk, butter, eggs, and other quick-to-perish items. The deceivingly simple icebox was typically made out of a hardwood or zinc exterior providing the first layer of insulation and filled with additional insulation materials such as sawdust, seaweed, corn husks, fur, and granulated cork. An ice block would be placed at the top of the ice box, and food would be placed below. This would push the cold air down to cool the foods at the bottom and allow hotter air to rise to cool off from the ice block. In more advanced systems, runoff from the melting ice block would be collected in the bottom for cooled drinking water.
While granulated cork was used in many early ice boxes in North America, there was still a problem. Even though granulated cork provided better insulation, unlike sawdust or corn husks, it had to traverse great distances to get to the Americas, making it a more expensive and hard-to-find option. But, this changed in 1891 when an accidental discovery at a life jacket manufacturing plant found that when granulated cork was subject to pressure and heat, it turned into a new material - expanded insulation cork. This material is lighter and has even better insulator properties, greatly expanding the roles cork insulation could fill in this rapidly developing industry.
By the mid-20th century, the time of the ice box had come and gone, with 85% of American homes having a refrigerator by 1944. However, cork's role in insulation was only beginning from the modern-day ice box - the travel cooler - to submarines, boats, home insulation, and even heat shields in space exploration. The only limit to what cork insulation can be used for is humanity's imagination.