This isn’t exactly rocket science, but buying an old fashioned ice bag and filling it with salt water (lots of salt!) will keep it from freezing even at sub-zero temperatures. The result is a soft and flexible, cold-as-ice bag that wraps around your injury with greater surface contact than your typical gel pack.
Edit: for those who didn’t bother to read further, commenters have mentioned that a solution of alcohol and water actually works better. Which is true, and I learned something today. Apparently, the process of converting icy slush to liquid requires more heat than just warming up extra cold water. Heat of fusion requirement I believe it’s called.
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I’ve also found that play dough makes a great ice pack when refrigerated. It’s cold but not too cold, soft, and malleable!
do y’all not use reuseable ice packs? they cost no more than a few euros, and you just toss them in the fridge or the freezer in between uses.
Instead of saltwater, you can also use a mixture of water and isopropyl alcohol.
I just use a bag of frozen peas haha
Edit- just remember to mark the bags (if you get more than one for rotation) so that you don’t eat them since you are basically repeatedly defrosting them with your body heat
You can also make a simple flour and water dough and freeze it.
You can even preshape it to contour to what you need it for.
This is a bad tip. The point of an ice pack is that it freezes to ice. It means that there is a latent heat of fusion that has been removed from the material, and that in order for it to warm up, the thing you are cooling has to provide that full latent heat of fusion back into it.
If it doesn’t freeze, the cooling effect only comes from the specific heat of the material, which can be an order of magnitude less than the heat of fusion.
Pro tip: double bag it. Salt water leaks are no joke.
You can do this same thing mixing water and isopropyl alcohol
I’m all of this type of stuff being more and more practical
What is an old-fashioned ice bag exactly, and where do you get it?
This is a good tip. I do something similar. I got those old-fashioned refillable ice/hot pack things. At first, I was using water, but then I had an idea.
I filled them with gel from those ice-packs that people get in the mail when they get food or whatever. The gel stays frozen for a long time, and as it melts it’s a good consistency to conform to your arm/legs/whatever
I have of those with a screw cap. You just fill it with ice and water. They are by far the best if you have an automatic ice maker.
This is a very misleading LPT.
Different commercially-made ice packs are formulated for different desired temperatures. For first-aid, ice packs freeze at 35-45F. For regular coolers, ice packs freeze at around 30F. For shipping coolers, ice packs might freeze at 0F or -10F.
Salt water will freeze between 10F and 30F. That’s too cold for muscle/joint therapy.
This is a terrible tip for two reasons.
the heat energy removed to cool one mL of water from 0 to -10C is about 40 joules. The energy removed to freeze one mL of water at 0C is about 300 joules, and THEN an additional 40 joules to cool to -10C. So your non frozen water could have almost a tenth the chilling power
ice packs require caution to avoid freezer burn and frost bite. One of the reasons they’re usable is that the outer surface rapidly warms up to 0C, even if the inside stays at -10C, since ice doesn’t flow. If you have liquid water at -10C, the outer surface will stay at -10C much longer, since water flows to keep the outside from warning up. While most people know not to apply directly ice packs directly to the skin, the corollary to that is that most people are idiots, and preventing water from freezing increases the risk of such injuries. The better solution is to use flexible ice packs or, less expensively, a bag of peas
Just use windshield washer fluid that’s rated for at least -15 C.
It’s a win-win for the wallet and the recovery process.
Do not cool it. It slows down the healing process. The doctor who himself came up with this idea of RICE (rest ice and elevation) retracted it recently.
Alcohol and water won’t work better. They separate and the water still freezes. If you want to DIY a gel pack, use cellulose powder.
1 The zip lock bag was not sturdy enough!
2 went & bought the old fashioned ice bag you described
3 I don’t know? I imagine with the alcohol & freezer action it won’t readily go rancid. Actually also use the ice bag from hospital & it’s been 3 weeks since I filled it
What’s an ice bag?
We used frozen peas after rugby games
I just use a bag of frozen peas.
Anyone else use dish soap instead? Freezes semi-solid, molds to joints, and won’t ruin your couch if it leaks. Not as cold as alcohol mixes, but gentler for long-term use.
Here’s what I do.
I take a small-ish ziplock bag and fill with ice. Place inside a larger bag, filled with really cold water. Wrap with a towel.
This will stay cold for a really long time.
About 15 years ago, I worked for a design firm. One of the clients, a national retail chain, tasked us with designing the perfect reusable ice pack for injuries.
We came up with dozens of designs. Our benchmark control for testing against was a frozen bag of peas. None of the designs did better, in terms of maintaining sub 10C temps on a simulated skin surface.
We started emulating the peas in further designs. We used soft gelatin/polymer balls suspended in an alcohol glycol mixture. That got close, but was still not as a good as a frozen bag of peas. Eventually that was the design we shipped, but I still remember—nothing beats a frozen bag of peas.