2022 Update: Thanks to everyone who shared solutions and suggestions!

I’ll highlight a few here:

Something like these flexible bladders might be a great solution to avoid problems with melted ice water in coolers, and food contamination.

I haven’t tried this yet, so I’m not sure how they’ll hold up to freezing. But, they look promising.

These collapsible water bottle bladders from Platypus have really good reviews. Platypus says these bladders can be frozen if laid “half-full on its side in freezer with all air purged. Do not overfill. Water expands as it freezes and this can burst your bottle.”

Several folks have suggested these “Big Ice” cube trays, which make 4″x 4″ (big) ice cube blocks. One mold makes 10 lbs. worth of ice cubes/blocks.

Here’s a similar variation.

These are a good compromise between giant blocks of ice and smaller cubes. 

Several folks suggested other great ice mold ideas and food-prep tools, including:

I haven’t tried these ideas yet. But, I will before our next beach or camping trip! I’ll do some experiments and report back when I do. 

If anyone uses these tools, or anything else like this, please tell me!

I’d love to find more good solutions and hear about your experience.

As always, y’all stay safe, happy and healthy!

Making Ice Blocks

It’s hard to believe, but Florida’s hurricane season is here again.

We all know what that means: time to make hurricane plans. Like every other hurricane season, I’ll be making ice blocks to keep in my freezer.

It makes me feel better to know that if we lose electricity, we might be able to keep our food from going bad.  Plus, we always have fun with these little science experiments.

I’ve even learned how to make beautiful, clear blocks of ice in my own freezer! It’s been fun, and I’ve great results.

When I wrote this article, a major hurricane was pointing right at us. The National Hurricane Center predicted it might hit Florida, so we needed to prepare. 

One of the best hurricane preparation tips we’ve found is to make block ice, and keep it in our freezer. If we lose electricity, it’ll keep our food safe. We do this every year. 

Plus, ice blocks are just useful to have around. It’s always nice to have good ready ice in the freezer Block ice is great for camping, boating, fishing and road trips.

Large chunks of ice last much longer than smaller ice cubes It’s also way cheaper than buying expensive Reddy ice, or trying to find block ice near me.

Block ice can be useful for:

  • Hurricane Prep
  • Camping
  • Boating
  • Fishing
  • Beach
  • Road trips
  • Barbecues
  • Parties
  • And more

In my many years of boating, adventuring and camping off-grid I’ve often wished I had ice blocks in my cooler.

Unfortunately, finding block ice near me is hard. And, it’s getting harder every year.

It used to be easy to grab a big block of ice at most grocery stores, but most stores stopped selling it. Today most people buy block from an specialized vendor or make it themselves.

Luckily it’s not hard to make ice blocks in your freezer. Almost anyone can do it with basic equipment and items found in most kitchens. There are also useful molds you can buy that give a nicer product.

Making block ice isn’t rocket science. It’s basically just freezing water in a large ice mold. But, it’s not also not as straightforward as it sounds.

I’ve learned tips and tricks to avoid:

  • Broken ice molds
  • Ice-water spills
  • Flooded, damaged freezers.
block ice mold water freezer measure
A systematic, experimental approach is best when making block ice

Wine bags and Flexible Bladders: The best block ice molds?

I love this idea. I’ve spent SO MUCH TIME looking for materials that would be good for making ice.

I never thought of this until I saw it mentioned in an outdoors forum.

Folks say that they’ve used old wine bladders. Others commented that they’ve found it difficult to clean used wine bags. Some say they prefer new, unused ones. Apparently these work pretty well for making ice blocks.

Molds to make block ice

Cardboard Boxes

Some people say they’ve had great luck using cardboard boxes as their form to make block ice.

I decided to give it a try using a cardboard almond milk box.

diy block ice mold
Flimsy molds like cardboard are not good choices for reusable block ice molds

I wouldn’t recommend using a regular milk carton because I wouldn’t feel confident that it was ever totally clean, and free from milk residue.

I was surprised, but even with the flexible cardboard, my mold broke several times.

It even broke when I completely cut the top of the container off, to allow room for vertical freezing expansion.

My guess is that the water froze from the top down, and left a liquid reservoir at the bottom of the mold.

When the bottom finally froze, there was no room for vertical expansion because the top was already frozen solid.

Some people use cardboard juice boxes as ice molds. They like the square and rectangular lines that the boxes produce.

Straight 90-degree ice blocks can allow for efficient packing in a cooler, and less dead air space.

Reducing dead air space is one of the best ways to makes block ice last longer.

If you use juice boxes, look for the type with a watertight screw lid.

Those are great because they’re less likely to leak while freezing. And, when they’re inside the cooler, they keep the melt-water contained inside the juice box. This is ideal because it won’t allow water to flood your cooler.

No matter what you use, always be sure to leave room for ice expansion. And, have a place for the water to go safely in case the ice molds break.

Plastic Bottles

Many folks use plastic milk jugs. But, most folks agree that milk bottles are not ideal.

They can leave irregular shapes in a cooler, which are hard to fill efficiently.

I find that they’re also prone to cracking during the freeze process. Still, they are not the worst choice.

They are better than some other types of containers because the bottles themselves are designed with expansion dimples.

Leave Ice in Mold, or Remove?

Once you have your frozen ice mold, it raises another question.

When you put it in the cooler, should you remove the ice from the mold? Or, leave it inside the mold?

On one hand, having cold ice-melt water contained within a sealed box would be nice for several reasons.

The ice melt-water might stay cold water colder for longer if it’s inside a mold. It would also provide good, clean, usable water if the box were clean enough.

On the other hand, cardboard can be an effective heat insulator. That isn’t ideal inside your cooler because you want the ice to absorb the cooler’s heat as efficiently as possible.

While making block ice in a cardboard almond milk box, I noticed that the cardboard appeared to negatively affect the block’s freezing process.

The water froze significantly slower than expected when inside the cardboard. This was true even while adding small layers of water at a time.

I also noticed that the outer perimeter of water froze quickly, but it was not frozen solid. There was often liquid, unfrozen water on the inside of the box. I also noticed that the bottom of the box failed to freeze consistently.

This was surprising because cold air and water should sink to the mold’s lowest point. To fix this problem, I used props to elevate the box off of the freezer bottom.

Cold air could then circulate beneath the box. This helped the ice freeze faster. When I try the juice box method again in the future, I’ll probably make one change to my method. I will remove one side of the rectangular mold, and leave that side of the ice mold open.

I’ll lay the mould on its back as the water freezes, and then remove the ice block from the cardboard before storing it in the cooler.

Do you need block ice?

First things first: is block ice the best solution for your needs?

To answer that, consider these questions:

  • How long do you need the ice to last?
  • Do you need fast cooling?
  • Will you have access to a freezer?
  • Will you be able to buy more ice?
  • Do you have freezer space to make block ice?
  • Is there enough cooler space for block ice and your food?
  • Do you have the proper equipment to make a mold?
  • Is there enough time to make block ice?

The biggest advantage of block ice is that it lasts much longer before melting.

This can be a lifesaver when planning a long trip without refrigeration. It’s why most people are interested in making block ice in the first place.

Tips for making block ice 1
Air bubbles and gaps can be avoided by adding small amounts of water at a time, and allowing them to freeze before adding more

Block ice is great because it melts much slower than other forms of ice.

If you need ice to last a long time because you’re out in the wilderness, fishing or sailing offshore in the ocean, block ice might be a great choice.

When block ice is the wrong choice

Block ice is a wonderful tool.

It’s great for certain situations. But, like any other tool, it’s not the best choice for every situation. Block ice isn’t necessarily any colder, or more powerful than other shapes of ice.

In fact, it probably won’t get your stuff as cold as smaller chunks of ice would. It will take longer to cool your cooler and its contents.

If you’re looking for fast cooling, then smaller chunks of ice, or even chips or shavings, will cool things faster.

Smaller cubes of ice have a greater amount of ice surface area. That allows faster heat-exchange, and much faster cooling. But, obviously smaller pieces of ice melt faster.

A combination of different ice shapes often works well.

Not the best shape

If you decide to use block ice, it’s important to pack your cooler correctly.

Cooler packing is an essential art and science.

Homemade block ice

A well-packed cooler should:

  • Minimize dead-air space
  • Maximize ice contact with items
  • Keep food from being contaminated by melt-water
  • Allow items to be easily accessible to minimize cooler open-time

Ideally, food in a cooler should be totally surrounded and packed in ice.

Small cubes can be great for this because they can fill into small gaps. Block ice can’t be snuggled into small spaces.

To solve this problem, some people use molds of different shapes and sizes to fill spaces efficiently. You can also use a mixture of block ice and smaller ice cubes, or even crushed ice.

Chipping block ice

Commercial fishermen often buy big ice blocks, but they don’t use it in block form.

They keep the ice inside a walk-in freezer, and go inside the freezer to chip or crush the ice into small pieces.

Tiny bits of ice can completely surround fish without damage. The problem with this is that for normal people like us, we can’t chip ice inside a walk-in-freezer.

For us, trying to chip the block ice would expose it to warm outside air.

So, any time at all spent chipping or crushing will rapidly melt our ice. It’s also very time and labor intensive to chip blocked ice. I don’t think it’s very practical outside of a commercial setting.

Block ice takes a long time to make. You really need to plan ahead, and know your space constraints. You’ll need to find a balance of several factors.

If you need your ice to last a long time, it’s important to make your block as large as possible.

Larger blocks provide more cooling power, and have less surface area relative to the volume of frozen water.

But, your blocks should not be made too big for your cooler. You still need to leave room for food.

If feasible, one idea would be if you have an extra cooler specifically dedicated to ice storage.

Block ice: Use it or lose it

Your block of ice will start melting as soon as you take it out of the freezer.

You’ll either need to start use it immediately, or use a freezer to store the ice until you need it.

Don’t flood your freezer!

Storing block ice in a freezer can be convenient, but risky.

Block ice contains a surprisingly large amount of water. Have a plan in place in case it melts unexpectedly. Unexpected melting could happen for any number of reasons:

  • Lost power
  • A freezer door left open
  • Broken freezer
  • A faulty freezer seal

Some freezers are designed to be self-defrosting, and some aren’t.

Depending on the specific model, freezers may or may not have a drain. They are generally not designed to handle large amounts of water from melting ice.

It’s best to plan ahead so you don’t have an unexpected meltdown! I store my store blocks of ice inside leak and water-proof containers to prevent accidental floods.

Block Ice Alternatives

Benefits of Ice Cubes

Ice cubes offer faster cooling than block ice. They are easier to find and sometimes easier to manage. They fill cooler spaces better.

Downsides of Ice Cubes

On the downside, ice cubes melt faster than large blocks of ice.

One good compromise would be to use these special big-block ice cubes.

They will give the benefit of slower melt time, and are still simple, easy and convenient to make.

Benefits of Dry Ice

Dry ice doesn’t leave water as it melts. Properly used, it can last for longer. It can keep food truly frozen, not just cold.

To find dry ice near you, check this page to find local dry ice retailers.

Downsides of Dry Ice

Dry ice can be dangerous. It might also be hard to find, depending on where you live.

It’s much more expensive than the alternatives, like making ice blocks at home in your freezer.

If you don’t use it correctly, it might damage your food and/or cooler.

Why make block ice?

There are many good reasons why people might want to make block ice:

  • Camping
  • Fishing
  • Road trips
  • Serving food
  • Food preservation
  • Hurricane and Emergency preparation

Block ice can be a great emergency backup for storm and hurricane season.

In a worst case scenario, if electricity is lost for days, it might give you enough time to eat your food, or find a solution before your food goes bad.

Block ice is also great for boating, off-grid camping, food storage and camping coolers. 

Experts in the outdoors community love block ice. When you’re away from electricity and civilization for days on end, it can make food-logistics much easier to plan.

Sailing and boating communities love block ice too.

They often use it instead of ready or cube ice because it lasts so much longer before melting.

Before boat refrigeration systems became common, block ice was the only way to keep food from spoiling on long boat trips.

In fact, before electricity and modern refrigerators, both boats and houses had “ice boxes” to store ice blocks, instead of refrigerators and coolers.

Today, block ice is less common. Electric freezers, refrigerators and coolers have become commonplace.

Advances in solar panel and battery technology have also helped make portable refrigerator and freezer technology accessible for ordinary consumers.

Brands like Dometic, ARB and Whynter, among others, have developed affordable portable, battery-powered freezers for everyday use.

Although the prices of these portable freezer prices are falling, these systems are still relatively expensive today.

For most people who only camp, boat or go off-grid for a few days per year, block ice is usually the best choice, by far.

Careful use of block ice might be a much more affordable and logical solution than spending thousands of dollars on a complicated and expensive electrical setup. That’s especially true if it will only be used occasionally.

While writing this article, I came across a few unexpected and hilarious uses for block ice, as well.

I wouldn’t necessarily recommend these uses, but they’re funny to imagine.

Some people said they put the ice blocks in their pool for a party.

Why would anyone do that? The water was hot, and they wanted to cool it down for their pool party.

Actually, a few people have emailed me about this. Some of the questions sounded like they’d been written mid-party, after a few beers.

This person said he bought a literal truck load of ice and dumped it into a swimming pool.

Even though the block of ice was massive, he said it didn’t even make a difference.

I’ve also seen many DIY block ice air conditioners. They use block ice, a cooler and a fan to circulate the cold air.

How Block Ice Works: Surface Area

It’s easy to think of ice as being cold, and sharing its cold temperature. And it does, sort of.

But the real effect at work is not really ice sharing its cold, but rather absorbing heat from its environment.

Ice absorbs heat through its surface area. As it warms, the outer surface gets warmer and melts away. A new, fresh, cold layer of ice is exposed, which absorbs more heat. That cycle repeats until the ice is fully melted and none remains.

solid block of ice made at home in freezer

More surface area equals faster cooling

This is why some restaurants serve shaved ice, or round cubes with a hole in the middle. Both of these shapes provide more surface area, and faster cooling than normal ice cubes.

Surface area is great for fast cooling. But, the ice melts quickly, and it won’t last very long. That might be bad if you’re on a multi-day trip and need ice to keep your food from spoiling.

Block ice has less surface area relative to its volume, so it melts slower and lasts longer.

Good idea even when you have a freezer

People who live in Florida and other tropical areas know that electricity can go out without notice.

I’ve lived in many places around the country and have never had such frequent power outages as my time here in Florida.

If you keep your freezer well-stocked, it might be a good idea to use block ice an emergency insurance policy.

In an emergency it might help save a freezer full of food from going bad. But, be careful of accidental melting, so you don’t ruin your freezer!

Should you drain the ice water?

There is a lot of debate about whether you should drain ice meltwater from your cooler.

Some people say that water in the bottom of a cooler makes remaining ice melt faster. Some people say that cold ice-melt water helps keep the cooler colder for longer.

For all of the raging debate online, I haven’t seen much discussion of one critical consideration: Food contamination.

Food safety and preservation should be a top priority.

I am not a food safety expert, but if your food packaging isn’t properly sealed, then make sure that ice-melt water doesn’t leak into food packaging to contaminate other food.

It can be helpful to use racks, tupperware and other tools to keep food away from sloshing ice melt-water.

Getting frozen ice out of the container

I expected this to be a difficult problem, but it was surprisingly easy.

To remove an ice block from its mold you only need a thin layer of ice to melt around the perimeter of the block.

It slides out easily. Just remove the mold from the freezer and let it sit for a few minutes. The outside of the mold will warm up and melt enough ice for the block to be removed.

Block ice mold water freezer home
Block ice is formed in a freezer-safe tupperware container

It probably won’t be necessary, but you can gently warm the outside walls of the mold and the block should slide out easily.

Good for Long trips

Block ice shows its value when on a long trip and there is no chance to make or buy more ice.

Even if more block ice is not available, it may be possible to add more ice to a cooler in the form of ready-ice cubes or other widely available ice.

Obviously this isn’t a possibility on long camping trips away from civilization. But, for road-trippers or boaters who have access to a marina, it may be a good way to extend the block ice and food.

How long will block ice last?

Under the right conditions, and when treated correctly, block ice can last for a very long time. The exact lifespan will depend on many variables, so no accurate prediction can be made for how long it will last.

  • Time cooler is open
  • Air volume of cooler
  • How densely packed the cooler is
  • Temperature of items when placed in cooler
  • Temperature of freezer when ice is made
  • Outside temperature
  • Thermal efficiency of cooler
  • Exposure to sunlight
  • Air ventilation around cooler

Tips for making block ice

Making block ice can take a long time.

The biggest tip is that you should start the process before you need it.

The time leading up to a big camping trip or outdoors adventure is often hectic and busy.

Planning ahead and doing things in an orderly and systematic way can help reduce chaos and stress.

It might take one day, or even a few days, depending on your situation and several factors:

  • Amount of ice you need to make
  • Container/Mold
  • Freezer Temperature
  • Freezer space

If you need many blocks of ice and are short on freezer space or molds you may need to leave even more time.

Bring Your Own Ice

In a crunch you could ask friends and family members to help you by making blocks in their freezers.

For example, on a group camping trip, if everyone brings a block of ice it can save a lot of time and energy, instead of putting the burden all on one person.

Steps and Tips for Making Block Ice

Things you’ll need:

  • Freezer space (make sure the mold fits your freezer space)
  • A clean bottle or container that’s easy to pour water from
  • A suitable mold for making block ice.
  • Make sure your mold fits your cooler and freezer space.
  • Test-pack your cooler to make sure it fits.
  • If you have lots of time, start with these two steps. If you’re short on time you can skip them.
    • Chill your mold by putting it in the freezer.
    • Pre-chill your bottle of water in the freezer or refrigerator

Thick plastic can act as a heat insulator, which will slow the freezing process.

Make sure you’re starting out with cold ingredients, including a cold ice mold. If you’re short on time you can skip this step.

Next, find a bottle or container of water that you’ll use to refill your mold. This should be easy to pour inside your freezer without spilling. I used a Nalgene bottle and really liked it because it has measurements built in.

We’re going to add water to our mold without moving it from the freezer. We do this to avoid carrying a sloshing, freezing mold of water around the kitchen.

Fill the bottle with cold tap water, and then put it in the fridge. You’ll use this later on to add water to your mold.

block ice molds at home
Cold water added from a water container allows block ice to freeze faster

Next, put the mold in the freezer.

Ideally the mold should stay in this spot until it’s frozen solid.

It’s important to leave the mold in place and avoid moving it. It’s very easy to accidentally spill sloshing water while carrying it in a big mold.

Make sure to arrange your freezer with this in mind— if you need something from the back, take it out before you start making ice so you don’t have to move it later.

If you do take the mold out for some reason— maybe to look at it, like I did—be careful!

The top surface can seem solidly frozen, but the water beneath is still liquid. It can lead to a tidal wave of sloshing ice water.

Pour some water into the mold. The exact amount of water will depend on your situation, including the size of your mold. The important thing here is to make sure you don’t add too much water.

Only pour enough to lay a solid layer of starter-ice in the mold.

The reason for pouring a small layer of water a time is to avoid having a top layer of ice skin over and leave the water beneath unfrozen.

A top layer of ice insulates the water beneath it and will take longer for the other water to freeze.

This method will also help avoid air bubbles that happen when a top layer freezes, but there’s water and air beneath it.

We want to avoid air bubbles in our block ice because they take up precious volume without any cooling benefit and can weaken the strength of the block.

After you pour a starter-layer in the ice mold, shut the freezer and let it start to freeze.

Make a note of your start time and start a timer to remind you to come back and add more water.

The exact duration of this waiting time will depend on the size of your mold, the temperature of your freezer, the amount of water you used and other factors.

I waited two hours between refill session and it was fine for me. More time will probably be better in this process.

When your timer goes off it’s time to add more water. Take the cold bottle of water from your fridge.

Leave the ice mold in place and add more water to the block.

Make a note of the time, set another timer and repeat.

If you noticed that the ice needed more time you can increase the time interval of your next refill session.

Keep repeating the process until your block of ice is made to the desired size.

If you don’t have enough time you may be able to shave some time off the process by using ice cubes.

To do this, place ice cubes in your mold and fill the surrounding area with water.

Because you’re starting from a frozen base it should freeze much faster than using water alone.

Avoiding contaminated food

Make sure that any food that makes contact with water is completely sealed and water-tight.

If water gets inside meat or other food it can contaminate food, water, and possibly cause illness.

Wire racks and creative use of stacking containers can keep food out of slushy ice water.

On the other hand, remember that direct contact with ice is the most reliable way to keep food safely chilled.

A fine balance must be struck between the two.

Submersion in ice water is better for cooling. But, it also carries an increased risk of contamination because water can find its way into any container.

Containers for making block ice

I’ve spent a lot of time looking for the perfect mold to make block ice.

block ice mold diy tupperware
I made block ice at home using a sturdy plastic tupperware container

Above all, a mold should be:

  • Freezer safe
  • Allow room for ice expansion
  • Material won’t be damaged by expanding ice
  • Don’t use anything that is glass, will shatter or break
  • Material is not too insulating

If you follow the method I describe below you will be adding water to your mold very slowly, a little bit at a time.

This will reduce the chances of your mold container breaking, but it’s always a possibility.

Before beginning, ask yourself: if you open your freezer and see a giant crack in your mold, would you be upset? If the answer is yes, don’t use it.

The perfect storm: the frozen flood

If you add water all at once your container it might form a skim of ice along the top surface. The rest of the water will still be liquid.

If that top sheet of ice cracks your mold, like a rigid plastic that doesn’t allow room for expansion, the liquid in the mold might escape all over your freezer, creating a big mess and possibly damaging your freezer, if it can’t handle the water. Be careful!

The size of your mold should be as big as you want the ice block to be, but not too big.

In general bigger is better because the ice block will last longer. But, don’t go crazy. If you make it too big it’ll be harder to deal with and it might prevent a good cooler packing arrangement.

If possible, I always recommend a cooler test-pack using your ice block mold container so you can see how everything fits together.

Ultimately, the perfect mold will depend on several factors.

  • Determine what size you need.
  • The mold should be as big as possible, but not too big.
  • Check to see if it will fit in both your freezer and cooler
  • Right material: It should be flexible, and not insulative
  • Ideally, a mold should allow for stacking in freezer while freezing
  • Easy to handle
  • Good ice block size

Ziplock bags to make block ice

I’m sad to say that I can’t recommend this method. Why am I sad about it? Because if it worked, it would be so nice and easy!

Zip lock bags have a lot going for them:

  • They’re supposed to be waterproof
  • They’re easy to find in almost any store near me
  • They come in various sizes, so they can be arranged nicely in a cooler

I’ve tried to make this work many times and have never had good results. Every time I’ve tried this, it’s leaked. I’ve even tried putting crushed ice in ziplock bags so it lasts longer. That leaked too.

I feel perplexed about this this because if you search for “block ice”, you’ll see so many people on the internet recommend this solution. I think people just recommend it and repeat the idea without ever having tried it.

I’ve also tried to put food inside the zip locks to keep food dry. Again, every time, I find that ice-melt water finds its way inside the ziplock bag.

As much as I wish this worked, I don’t recommend trying to use zip-lock bags to make block ice.

I’d love to hear tips from folks who have used this method successfully— maybe there is a secret or method I haven’t thought of. If you know how to make this work, please let me know!

What is Dry Ice?

Dry ice is a powerful tool. When dry ice is used correctly, it can deliver amazing results and dramatically extend the cooling life of ice. But, when used improperly, dry ice is dangerous and can damage coolers. Serious safety precautions must be taken.

Before using dry ice, users should ensure they are well-informed and know how to handle dry ice safely.

Users must be careful with dry ice for several reasons.

  • It can cause cause severe injuries.
  • Dry ice is so cold that when it makes contact with skin or sensitive tissue, it can leave serious burns.
  • Dry ice produces C02 gas, which can cause suffocation and build up dangerous levels of pressure within sealed containers.
  • When dry ice “melts” it turns from a solid into a gas— carbon dioxide (C02). This is actually not melting, but a process called sublimation, which is when a solid turns into a gas.

C02 is heavier than air, so it sinks down and settles into low-lying spaces. This displaces oxygen, and can create a suffocation hazard.

For example, imagine a car with the windows up and no ventilation. Now imagine there’s a cooler filled with dry ice inside the car. As the dry ice “melts” it releases C02. The C02 escapes from the cooler and displaces oxygen in the car. It could make you and/or other occupants lose consciousness, or worse. This is not a hypothetical scenario— there are at least several documented instances of this happening.

Dry ice has also caused health problems and injuries during hurricanes, as reported by this CDC bulletin.

Dry ice should never be put into an air-tight container, there must always be a way for the C02 gas to escape into a well-ventilated area.

Some coolers use a gasket and latches. These can be great features, but they can create an air-tight seal that will trap C02 gas inside. A sealed container will build pressure until it ruptures the container, possibly causing an explosion, injury or damage.

Carbon dioxide gas displaces oxygen which can create a serious suffocation hazard. Do not store dry ice in an enclosed space and make sure that there is enough ventilation to provide safe levels of oxygen.

Don’t let children or animals use or be around dry ice.

It can damage your food by causing “freeze burn”.

If dry ice is too close, or touching food it can freeze it. That’s great if your goal is to freeze food, but it can cause freezer-burn and damage food that’s not meant to be frozen.

Coolers may or may not be compatible with dry ice. If it comes into contact with plastic it can damage the plastic.

Other containers to use a molds

Gatorade and thick-plastic bottles are great to use as ice molds. They are sturdy, flexible, durable, and are a great way to reuse plastic before recycling. The thick plastic is nice because it is very unlikely to break, and the strong, reliable screw-top won’t leak.

Other plastic containers can be used as well. Again, it’s a great opportunity reuse plastic before recycling. Yogurt containers are great, as are milk jugs, and basically any other plastic food container.

With thinner and more brittle plastic, great care should be taken to avoid shattering the container. Again, with these, try to add smaller batches of water to freeze over time instead of filling it to the brim.

Smaller containers can be very useful for making ice blocks of various sizes. Different shaped containers can strike a useful balance between large blocks of ice and small ice cubes. Anything larger than an ice cube will offer an improvement, and irregular shapes can be useful to fill dead air space inside a cooler.

Many people talk about using non-stick baking dishes. With these it’s, a good idea to add water a little bit at a time, instead of all-at-once. Covering the container with a sturdy lid is useful because you can stack food on top of it, and use it like a shelf. This way you will avoid losing all of the freezer shelf space.

If you make a several ice blocks you can stack them on top of each other, although doing so may insulate the blocks and require more time to freeze. After you take the blocks out of your mold, you can put them into plastic bags to store them. It’s a good idea to store them inside a waterproof container after making your blocks to prevent an accidentally flooded freezer.

Be careful and prepare for unexpected cracks and leaks. If you make block ice frequently, eventually you may have a leak. Making block ice isn’t worth a flooded kitchen, or a damaged freezer.

Strategies to make block ice last longer

Even the most expensive, best cooler must be used correctly for optimal performance.

These steps are important with any cooler, and any type of ice, including both dry ice and block ice.

Pre-cool the cooler

If possible, make sure that your cooler is not hot from sitting out in the sun, outdoors, or in non-climate controlled storage.

Coolers are designed to retain stable temperatures. This works for both hot and cold.

So, if you start with a hot cooler, and the internal insulation is hot, it will take a long time for those materials to lose their heat.

If a cooler is excessively hot, consider learning how to wash the cooler, according to manufacturer instructions, with chilly water.

Keep the cooler indoors in a cool, air-conditioned setting before filling the cooler with chilled food.

Pre-cool the contents

Before putting anything into the cooler, try to ensure it is already cold.

This will help extend the life of the ice, and help keep the rest of the cooler cold. This basic principal applies to any cooler, and any form of ice you may use.

Pre-cooling items before going in the cooler will make your ice last much longer.

Keep Separate Coolers

Consider using separate coolers and giving each one a specific job.

It’s especially useful to designate one cooler for drinks, because that will probably be opened and accessed most frequently.

If children will be accessing the cooler, it may even be wise to designate one cooler especially for them, if they can’t be trusted to reliably close the cooler after use.

If possible, designate one cooler which is used solely for storage of meat and other food which does not need to be accessed frequently, i.e. only when cooking.

Remind everybody that each time a cooler lid is opened, hot air rushes in, and cold air rushes out.

Whenever possible, keep your cooler:

  • Closed
  • In the darkest, coolest place possible
  • Raised off of hot ground
  • Cool: Possibly under a wet towel

Use items quickly, and put it back in the cooler as soon as possible.

When outside of the cooler, items (Condiments, etc.) will absorb heat.

When they’re put back inside, that heat will leach out into the cooler, and warm everything up. It’ll make your ice work harder, and it’ll melt faster.

Put food back inside the cooler as quick as possible, and keep the cooler closed as much as possible.

Whenever possible, minimize the number of times a cooler is opened. Every trip inside the cooler releases cold air and introduces hot air, which the ice will have to work to cool.

Try to package food items individually before your trip. This will serve several purposes.

You’ll minimize time spend looking for stuff inside the cooler, which keeps cold air from escaping.

Plus you won’t put warm items back into the cooler after they’ve been outside.

Some things, especially condiments, are available in single-serve packets which don’t require refrigeration.

Everything that goes inside the cooler should be as cold as possible.

Freeze or cool as much stuff as possible before leaving home. It can be a good idea to freeze items even if they only require refrigeration.

Don’t put hot food, like leftovers, back into a cooler. Let it cool down as much as possible first. But, make sure to follow to safe food-handling practices.

Keep things in a sealed container whenever possible. But, make sure that things stay adequately cold. Dead-air space can insulate food and prevent cold air from cooling the food.

Even if you upgrade your system to a portable freezer or portable refrigerator, all of these best-practices will help increase the efficiency of your system.

Portable refrigerators and freezers might not require blocks of ice, but they do require electricity, which might be coming from a solar panel or an expensive battery bank. Efficiency is important even with electric cooling.

  • Pre Cook meals and freeze them before you go
  • You can cook frozen steaks from frozen. May be better than thawed.
  • Stack and arrange food in order of need: “combat loading” to reduce amount of time the cooler is open

Nalgene frozen busted warranty

While doing my block ice experiment, I used my Nalgene bottle. I wanted to say a few words about this.

frozen nalgene bottle ice

First, I love Nalgene for several reasons.

First, reusable bottles are a sign of thoughtfulness, conscientiousness, and intelligence.

Like saying please and thank-you, and not belching at the dinner table, using a reusable water bottle says something about a person— just like disposable plastic bottles do.

I won’t go off on a rant here about exactly what the messages say.

I think that Nalgene makes the best reusable water bottle on the market.

Some people may quibble with this. I’ll admit, I haven’t tried that many long-term because I’ve used Nalgene bottles for many years.

But, I keep a sharp eye out for different options, in case anything better is available.

When in camping and outdoors stores, I check water bottle selections pretty frequently.

So far, I have never seen anything that makes me want to switch.

Nalgene bottles stand up to serious abuse.

I’ve dropped them from crazy heights, frozen them them countless times, and generally treated them with total disregard.

They just work. They don’t leak, and they don’t break.

The next best thing about Nalgene is that if they do ever break, they’re covered by an insanely generous guarantee policy.

I love products like this, where you can buy it for life.

I can’t even guess how many times I’ve frozen Nalgene bottles, and they’ve never broken. I don’t know why, but one time recently, mine did.

Nalgene warranty
Damage from my block ice experiment

I was sad because I really liked the bottle, but my sadness turned to joy when I googled to see if their guarantee policy was still in effect. It was!

I submitted the online form, snapped a photo of the damaged bottle, and sent it off into the internet.

Less than a week, just like Christmas, the mailman delivered later a brand new replacement Nalgene bottle.

The Nalgene warranty really is the best in the market, in my opinion.

Should you dump cold water?

First, cold, melted ice water still provides cooling capabilities.

In fact, icy-cold ice water might cool stuff faster and more thoroughly than a solid block of ice, because it makes surface-contact and helps ensure heat/cold transmission.

If you need rapid cooling, you can pour water in with the ice. It will melt the ice faster, but it will help cool your drinks faster.

Water is a better insulator than air. So, if ice melts and cold water accumulates at the bottom of your freezer, don’t drain it, unless it might contaminate your food.

Cold air sinks. Ideally you’d put your ice above your food.

Salt ice and Pykrite

  • Salt ice
  • Pykrite saw dust

Other Ideas

Use meat thermometers and digital thermometers to monitor food temperatures.

Additional Sources:

My only concern with this method are the durability of the bags and possible ruptures at inconvenient times. The manufacturer says they’re freezer safe. I’ll report back after I do some experiments. 

One thing I love about these particular bags is that they don’t come with the little dispenser nozzle that seems to be common in wine bag applications.

I don’t trust brittle plastic bits to stand up to repeated freezing.

Luckily, these bags only have a screw-cap, which should be perfect. And, the manufacturer advertises that they’re suitable for freezing.