How to Make a Reusable Ice Pack

Quick answer

• Use a resealable bag and a salt-water solution.
• Freeze it solid.
• It’ll stay colder longer than plain water.
• Great for coolers and first aid.
• Super cheap to make.
• Easy to refill and reuse.

What to check first (do this before you drive out)

Before you even think about packing your cooler or heading out, get your ice game sorted. A good ice pack isn’t just about keeping drinks cold; it’s about preserving food and making sure your trip goes smoothly.

• Land manager / legality: For camping, this means knowing who owns the land you’re on. Is it National Forest, BLM, a State Park, or private? Each has its own rules about campfires, waste, and what you can bring in. Ignorance isn’t bliss out there.

• Access/road conditions: Before you point the rig towards the trailhead or campsite, check the conditions. Is the road paved, gravel, or just a suggestion? Does it require 4WD? Are there washouts? Mud? Snow? Don’t get stuck because you didn’t check. A quick call to the ranger station or a look at recent online reports can save you a lot of hassle.

• Fire restrictions + weather + wind: This is a big one. Fire restrictions can change daily. Check the official websites for the area you’re visiting. Also, look at the weather forecast, but don’t forget wind. High winds can make a cool evening feel frigid and can also be a fire hazard if restrictions are lifted.

• Water plan + waste plan (Leave No Trace): How much water do you need? Is there a reliable source where you’re going, or do you need to pack it all in? And what about waste? Pack it in, pack it out. That means trash, food scraps, and even gray water if you’re not near a designated disposal site.

• Safety (wildlife, distance to help, comms): Know what critters are in the area and how to store your food to avoid unwanted visitors. How far is the nearest town or ranger station? Do you have cell service? Consider a satellite communicator for remote areas. Better safe than sorry.

Step-by-step (field workflow)

Making your own ice packs is a simple process that pays off big time. Here’s how to do it right:

1. Gather your materials: You’ll need sturdy, resealable plastic bags (like freezer bags, not sandwich bags) and plain table salt. That’s it.

• Good: Using thick, high-quality freezer bags that won’t leak.
• Mistake: Using thin sandwich bags. They’ll split in the freezer or leak in your cooler.

For best results, we recommend using heavy-duty freezer bags to prevent leaks and ensure durability. These bags are designed to withstand freezing temperatures and repeated use.

2. Add water to the bag: Fill the bag about halfway with water. You want enough to freeze solid but leave room for expansion.

• Good: Leaving a good amount of headspace in the bag.
• Mistake: Filling the bag to the brim. The expanding ice can burst the bag.

3. Add the salt: Pour in a generous amount of salt. For a quart-sized bag, start with about 1/4 cup. You want enough to lower the freezing point significantly.

• Good: Eyeballing a good chunk of salt. More is generally better here.
• Mistake: Adding only a pinch of salt. It won’t make much difference.

To effectively lower the freezing point of your ice pack, a good quality table salt is essential. This common household item is key to making your ice pack stay colder for longer.

4. Seal the bag securely: Press out as much air as possible before sealing. Double-check that the zipper or seal is completely closed.

• Good: Getting all the air out and running your fingers along the seal multiple times.
• Mistake: Leaving air in the bag. It takes up space and can lead to leaks.

5. Mix it up: Gently agitate the bag to dissolve the salt into the water. You should see the salt disappearing.

• Good: Swishing it around until the water looks clear again.
• Mistake: Not mixing it enough. The salt won’t fully dissolve, and the freezing point won’t be lowered effectively.

6. Freeze it solid: Place the bag flat in your freezer. Let it freeze completely, which might take 12-24 hours depending on your freezer.

• Good: Laying the bag flat so it freezes evenly.
• Mistake: Stacking bags on top of each other while freezing. This can lead to uneven freezing and potential leaks.

7. Prepare your cooler: Once frozen, place your DIY ice packs in the bottom of your cooler. Add your food and drinks on top.

• Good: Pre-chilling your cooler before loading it.
• Mistake: Throwing warm items into a warm cooler with frozen packs. It’ll melt them faster.

To maximize the effectiveness of your homemade ice packs, pair them with a well-insulated cooler. A high-quality cooler will keep your contents colder for extended periods.

8. Replenish as needed: When the ice pack thaws, empty the salty water (down the drain, not on plants!), rinse the bag, and repeat the process.

• Good: Rinsing the bag well after use to prevent residual saltiness.
• Mistake: Just refreezing the slushy water. It won’t be as effective.

Common mistakes (and what happens if you ignore them)

Mistake	What it causes	Fix
Using thin sandwich bags	Leaks in the cooler, soggy food, wasted ice. Eventually, a mess.	Always use thick, freezer-grade resealable bags. Double-bag if you’re worried.
Not leaving enough headspace	Bag bursts in the freezer due to ice expansion. You get a block of ice stuck to your freezer shelf.	Fill bags only halfway and press out excess air before sealing.
Not adding enough salt	Ice melts just like plain water. Your food spoils, and your drinks are warm. Not much of an “ice pack” at all.	Use a good amount of salt – think 1/4 cup per quart bag. The saltier, the colder and longer it lasts.
Not mixing the salt and water	Salt settles at the bottom. The water doesn’t get cold enough, or it melts faster than it should. Inconsistent freezing.	Agitate the bag well after adding salt to ensure it dissolves completely.
Freezing bags stacked on top of each other	Uneven freezing, potential weak spots in the bags. Some parts might be frozen, others slushy.	Lay bags flat in the freezer to ensure even freezing.
Not pre-chilling the cooler	Your cooler acts like a warm sponge, absorbing the cold from your ice packs. Everything warms up faster.	Bring your cooler inside the night before, or put some sacrificial ice/ice packs in it to chill it down before loading.
Putting warm items directly on ice	The ice works overtime to cool your warm items, melting itself much faster.	Pack your cooler with pre-chilled food and drinks. Place ice packs on the bottom, then food, then more ice packs on top.
Not rinsing the bag after thawing	Residual salt can affect the taste of your food or drinks if it leaks. Can also make the bag sticky.	Empty the salty water, give the bag a quick rinse, and let it dry before refilling or storing.
Reusing a bag with holes	A slow, steady leak of salty water into your cooler. Eventually, everything gets wet.	Inspect your bags for any signs of wear or small holes before refilling and freezing.
Overfilling the cooler	Air gaps mean warm air gets in. It also makes it hard to pack efficiently, and things can shift, potentially damaging the ice packs.	Pack your cooler snugly. Fill empty spaces with more ice packs or towels to minimize air circulation.

Decision rules (simple if/then)

• If your trip is longer than three days, then use a mix of block ice and these DIY packs because block ice melts slower and provides a better base.
• If you’re camping in extreme heat, then add extra salt to your ice packs because the higher salt concentration will keep them frozen longer.
• If you’re concerned about leaks, then double-bag your salt-water mixture because it adds an extra layer of protection.
• If you’re packing raw meat, then place it at the bottom of the cooler, wrapped securely, because any leaks will go down and not contaminate other items.
• If you can’t get to a store for ice, then this DIY method is your go-to because it uses common household items.
• If you’re going car camping, then you can afford to bring more ice packs because weight isn’t a major concern.
• If you’re backpacking, then skip the DIY ice packs and focus on lightweight, non-perishable food because carrying frozen water is too much weight.
• If your cooler is old and leaky, then don’t rely solely on DIY ice packs; consider a better cooler or a more robust insulation method.
• If you find a leak in a frozen ice pack, then immediately remove it from the cooler and discard it to prevent a mess.
• If you want your ice packs to last even longer, then wrap them in a towel or newspaper inside the cooler because it adds insulation.
• If you’re worried about the salt affecting your food’s taste, then make sure the bags are sealed perfectly and consider using a food-grade salt if you’re really concerned.
• If you’re using these for a minor injury, then wrap the pack in a cloth before applying it to skin to avoid frostbite.

FAQ

How cold does a salt-water ice pack get?

It gets colder than plain frozen water, often below 0°F (-18°C), because the salt lowers the freezing point of water.

Can I reuse these ice packs?

Absolutely. Just empty the salty water, rinse the bag, and refill with fresh water and salt to freeze again.

How long will these last compared to regular ice?

They’ll typically stay frozen longer than ice cubes because of the salt’s effect on the freezing point.

What kind of salt should I use?

Regular table salt (sodium chloride) works best. Kosher salt or sea salt can also work, but table salt is cheapest and most common.

Can I use other liquids besides water?

You can, but water with salt is the simplest and most effective for general cooling. Other liquids might have different freezing points or spill concerns.

What if the bag leaks a little bit?

A small leak might not be a disaster, but it will create salty puddles in your cooler. Keep an eye on it and replace the bag if it gets worse.

How do I dispose of the salty water?

It’s just salt and water, so you can pour it down a drain or, if you’re outdoors, disperse it away from water sources and sensitive vegetation.

Are these safe for food storage?

Yes, as long as the bags are sealed properly and don’t leak. They’re a great, inexpensive way to keep your food cold.

What this page does NOT cover (and where to go next)

• Commercial cooler types and insulation ratings.
• Advanced food safety for extended trips.
• Specific camping locations and their regulations.
• Building a high-performance cooler from scratch.
• Using dry ice for extreme cooling needs.