# How to freeze a water container without deforming it?

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.

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?

# 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.

## Example

(with grape water flavour drops):

• 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 Nov 28 '14 at 18:38
• 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 Nov 28 '14 at 18:48
• @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 Jun 2 '17 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 Jun 2 '17 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.

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 Jun 19 '19 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 Jun 19 '19 at 21:34

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.

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