I've been watching a show on Netflix called "Jericho". In one episode, they used fertilizer and water to make ice (needed to bring someone's fever down). A little research verified that it is indeed possible.

But aside from the show's medical reason, I wonder in a post-shtf scenario, would ice really be that useful? Other food preservation methods such as drying and canning seem more practical... But the whole ice making process seemed pretty low-effort, so maybe worth considering? Maybe as a "moral booster" for a special treat once in a while, like iced tea or something? What do you all think?

Of course, this would all depend on whether or not you have the extra fertilizer laying around unused... Maybe it's better just used on the garden?

I just realized this is probably in the wrong forum. Sorry! Feel free to move it elsewhere, mods.

Ice is only as pointless as the effort to make or preserve it. In a real SHTF situation, which means prolonged (> 1 year, or permanent) lack of electricity, I think folks will find all sorts of uses for ice - preserving meds for instance. My great-great grandfather in 19th century Wisconsin maintained an outbuilding that he filled with ice every winter, which lasted through the summer and into the following winter. So they had a use for an entire barnful of ice, year round.

I have very pleasant memories of time spent in a Minnesota ice house at the resort we frequented - a building full of ice and sawdust. The ice was cut from the lake during the preceding winter and stored for the summer patrons. Digging it out and delivering it was a pleasant taks on a hot summer day.

In a marginal situation, ice would be the least of my concerns. I would go to an evaporative cooler (an open box surrounded by wet cloth) to keep foods longer. If ice could be collected seasonally and stored - fine; otherwie, forget it.

I don't know about the fertilizer thing; a lot of these techniques shown on TV are often farfetched and fictitious. I wouldn't use the boob tube as a training manual.

the heat energy required to dissolve solid crystals of potassium nitrate (KNO3) into a liquid solution is endothermic, meaning that heat must be added from the surroundings which will cool those surroundings...potassium nitrate may be a large enough component of the fertilizer compounds commonly called potash (the third % number in a designation like 6-6-6) to produce an endothermic cold compress

Ammonium Nitrate is what's used in those instant "ice" packs. I don't see it as a practical means of long-term refrigeration. Although I suppose you could allow the water to evaporate and then re-use it.

Reframe the question: is coolth a survival value? I spent most of my life in the boreal forests: cooling things off was seldom an issue. Now I am in the land of perpetual heat, and see a lot of resources devoted to creating the chill in an emergency: generators sized to support ac systems, residential structures close to the water )and close to the storm surge) to access sea breezes. Michael Crichton included a high tech tent ac unit in Congo, suggesting that high temp/high humidity interefered with sleep patterns and caused a measurable decrease in human performance.

I'd reserve it for medical uses unless it can be harvested in winter & stored. I don't know if you can generate enough temperature differential to use ice as an intermediate step instead of direct cold packs.

There are a lot of things you can do to adjust to hot conditions without depending upon a generator and air conditioning. One of the simplest is to adjust your schedule. Do the heavy work between sunrise and 9 AM to take advantage of the cool. The midday siesta isn't laziness - it is a very smart coping strategy for dealing with the heat.

I once did a dig in the Grand Canyon, right next to the suspension bridge and along the trail, where we were digging by 4 AM, knocked off at noon, retreated to our cabin until dinner, and then returned to the site in the evening, once it was in the shade. Worked pretty well and avoided a lot of sunstroke.

Shade is critical. Many native cultures adapt a ramada-like structure, basically a roof with open sides, that keeps the direct sun out, but catches the breezes. If you are hydrated and sweating, the slightest breeze will cool you nicely.

Most of my hot weather experience has been in the arid Southwest, which typically features low humidity. There is a big difference between 100 degrees with 20% humidity and 100 degrees and 80% humidity. To me dry conditions are far easier to deal with. If it gets hot enough, generally over 106F, about the only thing you can do is limit your exertion.

Ice is a luxury. Nice to have and useful, but not necessary. Look at most lesser-developed nations between the tropic lines. Little to no ice access, but they do quite well.

As for fevers, well, usually they worry the parent more than necessary. If your kid isn't seizing, they're probably OK. Cool moist compresses work just fine if needed.