Eli5: How did people make and keep ice in medieval times, and how do we manufacture ice cubes now ?

Question

Eli5: How did people make and keep ice in medieval times, and how do we manufacture ice cubes now ?

In: Technology

Answer 1

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.