How to fill and freeze reusable ice packs for coolers

What you need

• The packs and the funnel from the box (screw-top sets include one).
• A measuring cup — the water amount for each size is printed on the box and pack.
• Cold tap water.
• A towel and a flat space in the freezer.

Step 1: Measure the water

Each pack size takes a set amount of water. Too little leaves a dry, powdery patch that will not freeze into gel; too much stretches the pouch and makes it harder to seal. Measure it rather than guessing — owners who eyeball the first one usually measure the second.

Step 2: Pour slowly and mix as you go

Push the funnel into the opening and pour a little water at a time. After each pour, close the opening with your thumb or the cork and shake the pack so the water reaches the mix in the corners. Keep the powder moving away from the handle and the corners — that is where dry spots form. On hard cases, tilt the shell slightly away from you while filling so trapped air can escape.

Step 3: Push out the air and cap it

When all the water is in, lay the pack flat, gently press out as much air as you can, and screw the cap down firmly. For screw-top pouches, the cork goes in first, then the cap. Give it one more good shake and check there are no dry pockets left.

Step 4: The first freeze

Lay the packs flat in the freezer, not stacked, for the first freeze. Screw-top pouches need about 24 hours; hard cases do best with 48 hours. If you want a pouch to set curved — to wrap a dish or line a round tub — drape it over a bottle while it freezes.

After the first freeze, a single night in the freezer is enough to recharge a pack between trips.

Prefilled gel packs

Our prefilled gel packs skip every step above. The non-toxic gel is already sealed inside: unpack them, lay them flat in the freezer, and they are ready the next morning.

Packing filled ice packs in a cooler

Once your reusable ice packs are frozen, how you load them matters as much as how you filled them. Cold sinks and heat comes in from the top, so put one ice pack flat on the floor of the cooler, stand one against the wall that faces the sun, and lay one across the top of the food. Drinks go in the middle where they are easy to reach.

In a hard cooler, a full set of large ice packs will keep food cold for 24 to 48 hours. In a soft cooler, plan on a long day: use medium ice packs, keep the bag in the shade and open it as little as you can. A soft cooler loses cold through its walls faster, so the extra frozen mass helps.

Because our mix has a freezing point of 18°F, the packs run colder than a block of ice at 32°F. That temperature difference is why they keep food colder and stay cold longer — and why delicate produce should sit a layer away from the packs, while meat and frozen food can go right against them.

Which ice packs stay cold the longest

The longest cold comes from the most frozen mass: our 13" x 10" hard case ice packs and the large 14" x 10" and 15.8" x 11" pouches. Small ice packs and slim lunch packs are the right alternative for lunch boxes and day bags, where space matters more than a two-day hold. A good rule: big packs for the cooler, small ice packs for the bag, and enough of them to cover the floor.

All of them are durable, refreezable and built from tough material, so a careful first fill gives you years of cold drinks and safely chilled food without buying ice.

Care and storage

• Keep packs in the freezer between uses so they are always ready to go.
• Wipe them with warm soapy water after a trip and let them dry.
• Keep hooks, fillet knives and sharp gear away from pouches.
• Never reopen a filled pack — the cap stays on for its whole life.

Treated this way, a pack cycles between freezer and cooler for many seasons. That is the point of a reusable ice pack: one fill, years of cold.