I have a single, lonely blue ice pack in my freezer. Clever me: Last weekend I organized a park day with my friends when (the day of) I remembered I had only that one ice pack to work with. So I hit the internet to see what I could possibly do to make my own with two or three hours to spare. Luckily I had just the thing: dish sponges.
I know I could freeze a container of water for a giant ice cube, or a bunch of water bottles to melt into a refreshing drink, and these are good options. However, I didn't have the time, and I was walking about a mile and a half to the park so I wanted to pack light.
Why sponges make fantastic DIY ice packs
Sponges are cheap, so you can buy a few. They’re small and hold onto most of the water even after they warm so they're great for lunch boxes and small spaces. They’re lightweight, and they have an alternate purpose. So if you’re a sometimes-cooler-user like me, you can come home from the park, squeeze out the sponges, and use them for washing dishes. Now you have your freezer space back. Not to mention if there's a spill at the picnic, you're kind of a hero.
How to make sponge ice packs
Start with clean sponges. They don’t necessarily have to be new, but freezing old, used sponges seems unsettling, somehow. I think it makes more sense to use new sponges as ice packs, and then move them to their next stage of life as a dish sponge rather than the other way around.
Run each sponge under the tap so the whole thing is soaked through. Then squeeze it a tiny bit. The goal is to have the sponge maxed-out in capacity, but not losing too much. If you hold the sponge by one end, a slow drip of water will leak out the bottom. That’s great.
Put the sponge in a Ziploc or other small plastic bag, push out the air, and seal it. Put it in the freezer for about two hours, or until frozen hard. You can do this with as many sponges as you want.
Keep them in the plastic bag you froze them in and pack them in among your cold drinks and snacks. These ice-pack sponges are excellent for keeping food and drinks cool in tandem with a thermal, lined lunch box or cooler bag. Of course, always make sure the items you want to stay cold are already fridge-cold before you pack them. We spent a solid four hours in the park on an 80°F+ degree day and the cooler bag was still chilled by the time we wrapped up.