Tips for Making Block Ice

By Carolyn Shearlock, copyright 2011 . All rights reserved.

5 Tips for Block Ice

Okay, we all know the basics of how to make ice — put water in a container and stick it in the freezer.  But making block ice is a little different from making ice cubes and I’ve had some absolutely spectacular displays of things that can go wrong — so I thought I’d pass along what I’ve learned.

So why even make block ice?  If you use a cooler for food storage, block ice will last far longer than ice cubes.  And making your own has two advantages:  it costs less and you can make the size blocks that work best for you.  Sometimes, too, it can be hard to find block ice and so you have to make your own — that’s our problem.

Plan Ahead

Depending on how large a block you need, it will take a day or more for it to freeze solid from water.  So you can’t decide to make a block just a couple of hours before you’re leaving!

Sizing Up the Blocks

The first step in making your own block ice is to figure out what size block(s) will work best for you.  Then see if you can find a container that size . . . and if it will fit in your freezer.

After going out and buying a container that would totally fill my cooler, for example, I discovered that it wouldn’t fit in my freezer. Time to go back to the store.

I now have a slightly smaller container that fits in the freezer and I add some cube ice around the sides so that the bottom of the cooler is totally filled.  But I still have to do a lot of rearranging my freezer (read: cramming things into nooks and crannies) to make enough space for that bin.

Using Milk Jugs

Lots of people suggest using milk jugs (or other plastic bottles) to make block ice, and they can work well — but you need to know three things:

  1. The plastic will insulate the ice to a certain extent, so it will last even longer . . . but it won’t keep your food as cold as if it weren’t encased in plastic; and
  2. The sides of the bottles will bow out as the water freezes and expands, and you need to take this into consideration when figuring how many bottles you need.  With the bowing, you’ll have air gaps between the bottles.
  3. Just as with my large pan (see the story below), don’t fill the whole bottle with water and then let it freeze.  The expanding water will very possibly break the bottle.  Only fill it partway, let it freeze, then add more water, etc.

Freezing the Water

Well, my first mistake was filling my plastic bin with water in the kitchen sink, then trying to put it in the freezer.  It’s heavy, it sloshes, and it’s awkward.  With my first step, water sloshed down the front of my shirt.  The second step did in the front of my shorts.  Then, just as I was putting the bin in the freezer, the door starting closing on me; most of the remaining water went on the floor.

So I put the plastic bin on the shelf in the freezer and used a pitcher to fill it up . . . almost to the top of its 6″ height.

That was my second mistake.

I figured that as the water froze and expanded, it would all go upward.  I learned differently when I checked on it the next morning.

It seems that my plastic bin was no match for the force of the large block of ice . . . and cold water.  Apparently, long before it was all frozen, the expanding water and ice cracked the plastic.  And the water that wasn’t yet frozen gushed through those gaps . . . and formed a 1″ deep puddle of water on the bottom of the freezer . . . where I had other frozen food.  Of course, the water froze there, entombing numerous bags of frozen veggies and meat.  And the next morning found me having to defrost the freezer to get the resulting “ice sculpture” out and apart.  And then a trip to the store to get another bin.

Now I put the plastic bin in the freezer and add about 1/2″ of water at a time — wait about an hour for it to freeze, then add some more.  No more broken bins!

You may be able to avoid this problem by using a metal pan — but it can be hard to find a metal pan that’s as large as you’d like.

Making a Fast Block

If you need to make a block in a hurry, fill your container with ice cubes, then pour water over it — again, a little at a time.  But each layer will freeze in 30 minutes or less, and you’ll have a block in about 6 hours (or less, depending on how thick you want it).

I never thought that making ice could be so complicated . . .

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  1. Mick O'Gorman says:

    I don’t have a comment but a question please. Before I get to it I’d like to say I’ve taken refuge in your website and in dreaming of my first water voyage, a trip down the ICW with two friends. We’re all studying up. Now, my question – whereas you’ve detailed making ice blocks, I have no idea what a cruiser would need an ice block for! Thank you for you patience -


  2. Carolyn Shearlock says:

    Hi Mick!

    Enjoy your trip down the ICW — it’s a lot of fun, with great places to explore and lots of wildlife along the way.

    If you don’t have refrigeration, but are using an ice box or a cooler for your food storage, block ice will last a LOT longer than ice cubes (ice cubes will get things really cold, really fast — such as drink cans — but they also melt really fast). Lots of people who just take their boats out for a weekend don’t have refrigeration, but just pack up a big cooler at home . . . with a block of ice under the food bins.

    Thanks for reading!


  3. When we moved to our current house, we had a small chest freezer, but no fridge and got by via using empty 2-liters soda bottles filled with water which we froze and stuck in a cooler.

    Now, we have a large and too-deep deep freeze – I can’t reach the bottom. So we put water-filled 2-liters lying down across the bottom and covered with plywood. This makes everything easier to reach. When we lost electric for a week after a storm, the food all stayed frozen (except the stuff in the baskets).

    Also, those 2-liters are water storage in case the electricity were off longer, as we have a well and need electric to pump water.

    We keep a few above the plywood to use in coolers. I get milk delivered by a milkman and he grabs a couple to stick in the coolers instead of charging me for freezer packs.

    We also use them camping a lot. We pack frozen food in coolers with them, and intend to eat that food first. By the time we are eating the meals planned with non-refrigerated foods, they have thawed and provide potable water for the later part of the trip.

    The only downside is they are round instead of square. I prefer everything I store to be square. The Pepsi company needs to get into square bottles! ;)

    • Jpatti. You sound take a look into some of the large juice containers. They’re often squared off. You can also freeze the juice and use it as your ice block. As it melts pour into a cup and add your favorite rum. Lol

  4. Hi, Carolyn! One thing Brock & I have also used for block ice with great success has been Ziploc baggies. They come in all different sizes (quart to gallon, all have worked), hold water well and can be placed amongst the food & drink in varying configurations. Plus, we don’t have to store a large plastic container of any size onboard. If one tears eventually, well, you’re only out a Ziploc bag and some water.

  5. I like to take a case of bottled water and stash them away throughout the freezer. They are perfect for the cooler and when they melt..mmmm fresh water!

  6. Dan Thomas on Facebook says:

    Use milk jugs, fill 3/4 full let freez solid. Freeze with caps off. If it’s just day or week end trip. Fill the empty space in jugs with cold tap water. This gives you cold for cooler and cold drinking water. If for a longer stay, after the jugs have frozen solid add some more water to the jug and let this freeze solid too. Then just cap it, and place sealed jug in cooler. Keeps stuff cold the water is contained and still useable. For small coolers we use the quart Gatorade bottles the same away as mentioned above. These can be used in bigger coolers too, But they melt quicker. The quart bottles or 1/2 gallon milk jugs can be placed around food packages to keep cold evenly.

  7. This article was timed perfectly! I just spilled a Rubbermaid container all over the garage floor while trying to poor water in to it while it was in the freezer. We have 6 days until we are leaving so based on your article I will feed a few inches of water at a time in to the tub to keep it from expanding and cracking the container. Based on past experiences I made room and put the empty container in the freezer but I wasn’t able to reach the tub with the water so I had to pull out the container and I spilled it all over the garage floor. Thanks so much for your timely tips:)

  8. Large metal pans used in chafing dishes are available at stores that sell catering/restaurant supplies, including Sam’s. The only problem would be that they are not airtight and the water would have to be frozen before sailing. It’s easy to get the ice out of them if needed.

  9. A quick experiment for those with a freezer to try and answer. As I have a boat and not a yacht, I can’t. I was emphatically told by a surveyor a long time ago that yachts have ice makers, boats do not…

    Since saltwater freezes at a lower temperature (-5°f if memory serves), wouldn’t it make sense to use saltwater in gallon jugs to compensate for any insulating of the plastic? Assuming, of course, that you can find a freezer that gets that cold.

  10. I prefer smaller block containers. I fill these to different heights so I can wedge the custom blocks as needed in the cooler especi’ally for extended trips. In the past I tried gallon jugs and 2 liter soda ‘bottles but then can’t fit enough food in the cooler! Lots of smaller blocks seems to work for me

    • That’s a good idea, depending on how you arrange your cooler and food. I put the ice on the bottom, then have metal racks and bins that the food goes in to keep it out of the melt water.

  11. Thank you for another great article Carolyn; you had me smiling and laughing, not at you but at myself for having many of the same experiences with making block ice.

  12. Though I’ve not tried it, I understand that a mixture 6:1 of water to saw dust or other wood pulp will make blocks of ice that last an order of magnitude longer than just plain water. This is called Pykrete
    ( I bet this would be really good for a long trip. The downside, I imagine, is the cleanup when it finally does melt. I suppose a little fore-thought into containing the mess would be in order.

  13. I know its a luxury but I’ve also use two coolers. One for drinks which gets opened more often and one for just food. I transfer the ice blocks as needed.

  14. I mostly use 32 oz yogurt containers. They will deform some, but if I crack one, I’m going to eat more yogurt soon. I don’t really have room to do big blocks but anything bigger than cubes makes a difference. You can leave the container on (and have water to drink eventually) or pop the giant cubes out.

  15. Great article Carolyn!

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