The final ice pack will freeze solid and within 30 minutes return to a semi-frozen gel state and stay that way for several hours.
If you fill your bag more full, it will of course stay colder longer, but these slender, thin ice packs fit nicely in our freezer without taking up extra space and last well past lunch, if not until we get home!
Having an ice pack for your lunch is a great idea when it comes to keeping cold things cold, but did you know you can make them yourself? They're ridiculously easy, inexpensive, and easy to reuse in your kitchen if their services are no longer needed. Trust us, your fresh salad or tuna sandwich will thank you!
What You Need
1 plastic zip top freezer bag (or vacuum seal type)
1/2 cup liquid dish soap (your choice)
3 drops food coloring (optional)
1 glass jar (optional)
1. Open Bag: Although this sounds like a silly first step, it's an important one. Even though it's not rocket science to squirt soap into a bag, any residual soap could end up on your lunch, so we take an extra second to roll back the lip of the bag to eliminate any chance of contact later on.
2. Add Soap: Although you can just squirt the soap right in the bag, we use a small jar to help hold the bag open and also to keep the zip-closure out of the way. This ensures that we won't have any external soap that could come in contact with our tasty lunches or picnic food!
3. Add Food Coloring: Although ice packs won't be confused for a snack by adults, they could be mistaken by children as such. Add a few drops of food coloring to the mix if you'd like to ensure they don't look like your typical frozen treat (or just for fun, because purple ice packs are cool!).
4. Remove Air: This is easiest done on the first try, once you flip it upright to squeeze any excess out of the bag, you'll have new found air bubbles that will need to work their way to the surface. Keep the bag flat and let it almost flow out the top and seal right before it gets to the end. You can of course choose any method you wish, this one just happens to work well for us.
5. Freeze: Your ice pack will take to whatever shape it rests on in your freezer and even though it will spend most of it's time in your lunch box as a thick cold gel, when it's first removed from the freezer it's more solid than not (depending on the size of your ice pack). Sometimes we keep them flat, other times we roll them up and store them in a glass until frozen, that way it will keep your fruit perfectly chilled, but not your peanut butter sandwich.
6. Tips On Using These packs will work forever as long as you take care of them. If you're worried about them leaking you can use a double bag or a vacuum seal bag. They're super inexpensive to make and at only a few pennies a piece, you could make one for each day of the week or different shapes or sizes.
Related: 10 Plastic-Free Lunch Boxes
(Images: Sarah Rae Trover)
(Originally published April 13, 2010)