Eli5: How did people make and keep ice in medieval times, and how do we manufacture ice cubes now ?
In: Technology
In old times people would cut big ice blocks in winter from rivers, lakes etc. Then store them in storage buildings, away from sources of heat or warmth. The bigger the block is the longer it takes for it to melt. Additional insulation would also be used to keep it cold for longer. They would prepare it every winter and sustain on it throughout the year until next winter.
Quite a few older cities have remains of ice storage warehouses as it was widely used in industries.
They cut is out of frozen lakes and stored it in an “ice house” where they insulated the blocks with sawdust that came from lumber mills. Its amazing how long the ice can stay frozen when insulated like that.
Here’s a photo of the ice cutting operation: https://19thcenturywellington.wordpress.com/wp-content/uploads/2013/08/970553-men-harvest-ice-at-west-lake-park-date-unk.jpg
Old time: Let a lake or river freeze. Then cut ice blocks, store in insulated ice houses, cover with sawdust for extra insulation and use it during the warmer months and hope to not run out of it.
Now: use some freezers to freeze the water in molds. Alternatively, use metal mold in vertical position (holes on the side) with refrigeration tubes inside it, this freeze the mold. Flow water on the mold, the water freeze. When there is enough ice you reverse the refrigeration cycle, warming up the mold and releasing the ice. Once released put back the cycle in “freeze mode” and repeat.
nobody mentioned this yet, but as early as tang dynasty (around 9th century), while they were tweaking with saltpetre and sulphur to make gunpowder, they noticed how saltpetre can react with water and able to turn it into ice. so they’d get saltpetre from quarries and use it to make ice in the summer. though it would’ve probably restricted to aristocrats and nobilities.
I suspect this is more of a r/askhistory or r/askhistorians type question. The quality of the answers tends to be better vetted.
As far as I know, most of Europe didn’t really have the kind of winters needed for large scale winter ice production. Large scale ice harvesting of frozen lakes and rivers didn’t really happen until the early 1800s, and the European arrival into the Americas. In the mid 1800s the northern states of US and Canada actually exported a lot of ice to the south, Caribbean and Europe.
In the winter when rivers and lakes/ponds froze over, large blocks of ice would be carved out and taken to an icehouse for storage till summer. The ice covered in straw, mud or even manure which insulated it and the large blocks prevented it from thawing completely.
There are some stories of ultra rich nobilty having servants go to some remote mountain or glacier and bring back ice to serve at parties. But that was more of a rare event and for special occasions, not the norm.
In ancient Egypt and other very dry climates they could use the massive thermal swing between day and ice, plus the low humidity to trigger evaporative cooling to make ice in buildings called [Yakhchāl](https://en.wikipedia.org/wiki/Yakhch%C4%81l)
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