Easy, cheap, and cold.
No, I’m not talking about my past life as a contract killer…
If you get injured, the acronym you use to remember the treatment regime is R.I.C.E.R. This stands for Rest, Ice, Compression, Elevation, and Refer. They’re all pretty obvious, maybe except for refer – it means to see a doctor if it is serious, debilitating, or fails to resolve within a day or so. Anyway, ice is sometimes inconvenient to use – it gets wet as it melts, you have to remember to fill the ice cube tray, and your children steal all of the ice cubes to make slushies when you’re not looking. Well, not any more! I’ve created the perfect ice pack to treat injuries. This ice pack doesn’t make a puddle, it doesn’t have lumps of ice, and no-one is going to steal it to make cold drinks.
To make it, you’ll need the following:
Three teaspoons of water storage crystals. The brand I use is Homewares from Bunnings – where you live might not have the same brand but it should have the same stuff. It is tiny white crystals like sugar, that swell up fifty to one hundred times their original size when they are saturated with water. Use the remainder to make a second or third ice pack, or on your potted plants.
300 ml of methylated spirits. This stops the water in the ice pack from freezing solid – alcohol freezes at a much lower temperature than a domestic freezer can achieve. 
The amount was selected to maximise the frozen water and yet minimise the size of the ice crystals. If you don’t want to use methylated spirits, you could use Vodka instead…
Blue food colour. You want to know if the ice pack springs a leak in the freezer and you want to make sure you don’t mistake it for food. There aren’t many foods that are bright blue.
2 Litre (about US 1/2 gallon) wine cask bladder. Nothing comes close – they are robust, inexpensive, easy to fill and readily obtainable. Empty it out carefully (-: lever the stopper off with a spoon or similar, rinse it, and it’s ready to use.
Method:
1. Using a spoon or a spatula lever the tap out of the circular hole in the bladder.
2. Put three teaspoons of water storage crystals in the bladder.
3. Add 1.2 litres (2.5 pints) of water to the bag, using a funnel.
4. Add 300 ml (10 US fluid ounces) of methylated spirits to the bladder using the funnel again.
5. Add three to five drops of blue food colour to the bag.
6. Replace the stopper fully, shake the bladder, and leave it overnight.
7. Squeeze most of the air out of the bladder, leaving a little in the stopper area.
8. Freeze the ice pack overnight.
9. Once it is frozen, remove it from the freezer.
10. Bend it up and down all over to work the trapped air into the spaces between the ice crystals.
If you have a different sized bladder, just scale the volume of crystals and liquid appropriately. You don’t want the bladder too full or it doesn’t bend around your limb as effectively.
Be careful with this ice pack – it WILL get cold enough to give you frostbite! Always use a wet towel between your skin and the ice pack to protect your skin from freezing.
PS – it’s also great for rapidly cooling drinks in cans and bottles, to help while away the hours until your next run.