Eli5: How did people make and keep ice in medieval times, and how do we manufacture ice cubes now ?
In: Technology
Ice was taken in large chunks from frozen lakes and stored. When you store a huge chunk of ice in an insulated building, it melts very slowly.
Ice is made now using chemical refrigeratants. These are chemicals that remove heat from nearby stuff very rapidly. Remove enough heat from water and it turns to ice.
The refrigerants are then cooled off and used again.
Fun fact: Almost all of our chemical refrigerants are green house gases that, when leaked, lead to global climate change. Many climate change experts believe refrigerants are the number one thing that should be regulated to prevent climate change. Modern Refrigerants are 700-1000 times more warming to the planet than C02.
[Michigan Ice Tools with Jim Cassell (youtube.com)](https://www.youtube.com/watch?v=YxQp6tU5EXg)
Here’s a relevant and interesting YT video about ice harvesting tools.
Big ice block harvested from glaciers.
Water has a high heat capacity plus latent heat capacity. Doesn’t melt easily.
Insulate so less heat dissipates.
Your ice stays intact long enough to make a gin and tonic.
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You can find Roman ice wells in Spain. If you want to learn more, look for that. I was researching it not so long ago. The whole ice trade was crazy.
My friend is from Connecticut, and all through high school and college he worked at a replica town from the Revolutionary War. During winter they would bring ice-cutting sleighs out onto the frozen lake and cut up big hunk of ice to store in a barn with hay.
Before we figured out how to cool things mechanically (refrigeration), ice was harvested in the winter or where there is ice perpetually. It would be cut into large blocks because larger ice cubes melt slower, and transported to ice houses, a type of building partially underground and with lots of insulation, usually straw. Being underground and insulated means the temperature didn’t change much, and you could keep ice for months. Even so, you would put away hundreds of pounds of ice just to have a few dozen pounds in summer. The whole process takes a lot of manual labor and space for a small product, so only the really rich would have ice far away from where it was harvested.
Now, we have machines that can cool water really fast (refrigeration) and can make ice basically whenever we want. Depending on how you want your ice cubes, it’s made slightly differently (tubes of water being cooled, flat sheets of water being broken up, or cold pipes making ice with holes in it), but uses modern refrigeration. Because of how common and cheap to run these machines are, you can get a dozen pounds of ice for a few dollars.
People don’t realise this but ice is actually quite hard to melt, especially when it’s gathered in large quantities. I remember when I was a kid it snowed unexpectedly in winter with a lot more snow than the area is used to. School was out and they brought bulldozers to clear out the schoolyard and they piled the snow up to the side making a small mound about 7ft tall and 20-30ft wide. That mound did not melt completely until late spring, nearly half a year later.
In a simillar fashion ice was harvested by professionals called Icemen who would collect ice from frozen lakes or mountains both during the winter and summer if there were peaks nearby that still had snow. The ice would be cut into blocks and stored in ice houses. This occupation existed since antiquity up until the early 20th century. The stored ice would actually melt very slowly, which meant that it could easily last months or years in the ice house with minimal losses due to melting. When someone ordered for ice they’d deliver it in blocks, which still lasted many days each but obviously melted faster. Of course your average peasant wouldn’t be the one buying ice by the block but richer people and lords would buy a lot of it and have a special area in their cellars for chilled foods or would use the ice to chill their wine or other drinks. Cellars were also fairly cold themselves so depending on the exact area sometimes the ice wasn’t even necessary.
Towns and villages also had cellars or purpose built storehouses meant to be as cold as possible to preserve everyone’s food collectively. Ice was also used for the transport of goods like vegetables or fruits by ship, which again took many months to completely melt due to the amount of ice used.
There was a great episode of Gastropod that covers this ICYI
https://gastropod.com/the-birth-of-cool-how-refrigeration-changed-everything/
In the Netherlands ice was usually harvested for pubs and cafes in the winter from the river, imagine that beginning scene from frozen, and stored in the basement of the pub. It would melt during the summer but would keep beer cold for a pretty long time.
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