I like to take a frozen Nalgene bottle of water to my Bikram Yoga class. The problem is, every bottle I have used so far becomes deformed and, as can be seen in the picture below, the bottom bulges out making it difficult or impossible for it to stand upright until some of the ice melts and it pops back in.

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Eventually, the exposure to expanding substance over time causes the bottle to break. What can I do to freeze my water without deforming the container?


8 Answers 8


Don't fill the container

You can't win in a battle against the laws of physics. Water expands when it freezes, so you need to leave some room in your bottle for it to expand into. What I find works best is to fill your bottle just over half, then freeze it on its side. This will give the ice more room to expand than if you freeze it upright. When you grab your bottle from the freezer, top it up with cold water; the ice being frozen along the length of your bottle will rapidly cool the water, and you'll have a easier time getting water out when you want a drink.


(with grape water flavour drops):

out of the freezer full of water

  • 1
    I did exactly that thinking it would expand towards the empty part of the bottle and even left the lid nozzle open so that the air can escape in the process. But somehow, it "decided" to bulge out on the bottom again
    – amphibient
    Commented Nov 28, 2014 at 18:38
  • 2
    That's because of the shape of your bottle, there's more volume in the bottom. Either freeze less water, tilt the bottle so less water accumulates in the bottom, or get a different bottle that freezes better.
    – ShemSeger
    Commented Nov 28, 2014 at 18:48
  • 3
    @amphibient - the top freezes first (ice floats), and in that wavy shaped bottle the narrowest part will also freeze more quickly. The result is, by the time enough water has frozen exert pressure, the top has a nice thick layer of ice which makes it much easier (with gravity assisting) for the water to shove the bottom out and down instead of shove the solid ice cap upwards. Knocking a hole in that frozen layer or freezing sideways means a thinner ice layer, which is easier to break than the bottle when under pressure.
    – Megha
    Commented Jun 2, 2017 at 5:03
  • Also, if you still want a fully-frozen water bottle, you can add more water and re-freeze a halfway frozen bottle like this. With half already frozen (and not expanding again) the pressure is less, the initial ice already distributed (and so less likely to bottleneck) and so the risk to the bottle is less - though you will still need some expansion-room.
    – Megha
    Commented Jun 2, 2017 at 5:08

I have found that soda pop bottles are designed for higher pressure and don't deform as badly. Plus they are cheap to replace. In general a soda pop bottle filled to just the start of the shoulder won't break.

Water freezes from the top down. In a tall bottle, water freezing at the top gets a grip on the sides, and so as the water freezes down, the expansion pushes out the bottom.

Laying it on its side, and not quite filling it to the half way mark, the slab of surface ice is a wedge that can easily be lifted.

In addition: If you freeze the water, then add ice water from the fridge to fill up the bottle, the resulting mix won't melt very fast.

Finally, put the bottle in a thick sock and it will insulate it, keeping it cold longer.

Addition: With a 2 liter pop bottle, you can fill them to about 1" below the upper shoulder and freeze them standing upright. The force of freezing lifts surface of the interior ice. You can then top up the bottle and refreeze on it's side. We store frozen crabapple juice this way for later jelly making

If you are freezing larger containers, such as barrels, the following technique works well:

  1. Put the barrel on a pallet. This allows the bottom to freeze as fast as the sides.

  2. Float 3-4 inches of styrofoam peanuts, or broken up styrofoam on top. This slows the ice formation on the top, and also weakens it. The core then breaks through the top when the pressure gets high, instead of pushing out the bottom.


Don't freeze the bottle - fill it with ice cubes. Better still, don't use ice cubes, use ice sticks that fit in the neck of bottles.

  • Alternative sticks I've found (come in different sizes too; also some of them use actual water that you can drink when it melts): amazon.com/gp/product/B01I888HN2
    – Andrew
    Commented Jun 19, 2019 at 21:33

I would take one of the flexible bottles like the platypus brand and make sure to fill it only about 70%. You can not beat the physics: Water expands if you freeze it. If you have a flexible bottle and make sure it is not full, the water will be allowed to take its form without damaging the bottle. To be clearly on point: You can not freeze a water container without deforming it. You can actually blast rocks wiht freezing water. This is what happens in the Alps all the time and gives us those talus slopes of all kinds.

  • You can't? It's impossible? Regardless of material?
    – Andrew
    Commented Jun 19, 2019 at 21:34
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    @Andrew steel pressure pipe can be broken by the expansion of ice (YouTube link)
    – Chris H
    Commented Jun 11, 2021 at 15:20
  • @ChrisH Cool, but he froze it with liquid nitrogen and with 100% capacity. What about 50% or 75%? What if the water "has room to expand"? (Though I'm not sure I know what I'm talking about here since the remaining capacity would be air.) I would think tilting a bottle on its side would give more freeze leeway before an explosion.
    – Andrew
    Commented Jun 12, 2021 at 21:35
  • 1
    @Andrew the liquid nitrogen speeds things up, and might make the rupture more dramatic compared to slow freezing that might possibly cause bulging and a leak (both because of the fast freezing and because steel becomes more brittle at those temperatures. As air is compressible, leaving some space would help a lot, so long as the water can expand freely If I want a bottle of ice/water I freeze a disposable plastic water bottle on its side, half full, then fill the remainder with chilled water; these bottle might survive by deforming anyway.
    – Chris H
    Commented Jun 13, 2021 at 8:29
  • ... the phase diagram of water is interesting. If you can go to very high pressures indeed (like 10 000 atmospheres) you can get different crystal structures, and water is solid at high temperatures. The only way to do that is in tiny quantities in a diamond anvil cell
    – Chris H
    Commented Jun 13, 2021 at 8:32

If you are okay with taking a more "hands on" approach, then it works to put the water in and then when the top layer is frozen over, then you poke a hole in the layer so that the rest of the expanding ice is not stuck.


Experiment: 32oz Nalgene -- straight sides but it narrows at the top where the cap is. I filled it 1/3, let it freeze. Filled it 2/3, let it freeze. Added some more a few more times, adding very little water when I was in the area where it narrows a bit. At all times in the freezer it was vertical.

Result: There now sits a bottle in my freezer that does not appear to have deformed in the slightest and which is virtually 100% full of ice. It took something like a week, but most of that time was dealing with the neck. It could be done much faster I was only after 90% full.

Round 2: Another virtually identical bottle. Half full, the about 85% full. No deformation.

  • That's a good approach. Often a little chilled water in the top is a good thing, so you can go for 80-90%, then top up without freezing again
    – Chris H
    Commented Jun 24, 2021 at 12:58
  • @ChrisH The plan for these bottles is additional water on long hikes. It doesn't matter that they will start as 100% ice. Commented Jun 25, 2021 at 4:08
  • Perfect then (personally I tend to just fill with ice, then fill with water, if plenty of ice is available, or freeze half full on the side if not, but your approach gets a greater proportion of ice
    – Chris H
    Commented Jun 25, 2021 at 7:39

Some container with the shape of conical (upside down) bucket is perfect for this. When it freezes, the ice should move upwards.


I've read that water expands around 9% when frozen, so you need to make sure the water has room to expand without a problem. You need to make sure that the air can either escape, or there is not too much air in the bottle before freezing. With plastic bottles from the store you're able to kinda "suck out" some air, which will deform the bottle a bit, but it won't explode in exchange hopefully. But this all is just a bit of theory

I will tomorrow try and freeze a 1,5l water bottle by taking out 0,5l out, so only 75% of the water remain. Then I'm gonna suck out as much air as possible, hopefully around or more than 100ml of air, so that the water will have no problem expanding around 90ml without the air pressure causing problems. I report on my experiment in case it failed

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