Someone I knew was a Korean war combat vet. He said that they made coffee by putting water and coffee grounds in a helmet (metal) then hung the helmet over a fire to brew it. So far, so good. He said when it was done they would stick a freezing cold bayonet into the brew and this would cause the grounds to settle out for “cleaner” pouring. Huh? Does this have any scientific basis? I guess I could try it at home with a regular pot but I’m too lazy.
The way I’ve seen it done, you simply add some cold water (or snow). But yeah, I guess a freezing cold metal tool could lower the temperature a bit too.
I can’t say I’ve seen it with a cold object but I’ve seen the effect a number of times with cold water. My first company command included the battalion food service section and I typically lived near them in the field. The standard way to make coffee for 600 in the field was* to add coffee to water in a large pot and simmer. That was this millennium. The grounds were on top during heating. Adding a little cold water really does work pretty well to drop the grounds to the bottom.
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- Later filter packs to dump in the pot started coming through the system.
I have seen it done with a bit of salt.
Legitimate methods of making coffee:
Ones that work,
… I guess that’s it. 