Why does Coke go flat with ice?

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#3019663 10-Jan-2023 15:52

Your ice is too cold. Little icy parts on the surface will give the bubbles points to form on. Bars always have ice on the verge of melting. Also a dry glass with have more opportunities for the gas to come out.

Try putting your ice in the glass, putting some water in, swishing it around so that the surface of the ice is now warmer as its cooled off that water and frozen some of it and the glass is wet then tip out the excess and see how you go for flatness.

This is part of the reason that bars have those glass washing things at the sink.

Also are you pouring a warm can into ice or is the can in the fridge already?

Richard rich.ms

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#3019676 10-Jan-2023 16:22

The can is in the fridge first.

The melting ice thing sounds like it's worth a go! Thanks.

frankv

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#3020362 12-Jan-2023 09:18

johno1234:

frankv:

On a similar note, however, I believe that Coke in the 2.25L bottles goes flat faster than in 1.5L bottles. So 3 day old 2.25L Coke is flatter than 3 day old 1.5L Coke.

You mean once half the Coke is consumed? That makes sense as lower pressure and higher available volume in the bottle. My distant memory is trying to say something about partial pressure to me.

Yes, a larger volume of air in the bottle would mean that more CO2 would come out of solution to achieve equilibrium. But a larger volume of liquid would mean that it would be a lower percentage. i.e. It's the ratio of air to liquid (and time) that controls the flatness. After 500ml consumption, the 2.25L has 1.75L liquid and 500ml air whereas the 1.5L has 1L liquid and 500ml air. So, for the first 1.5L consumed, the 2.25L should be less flat than the 1.5L, because the air volume would be the same. For anything beyond 1.5L, the second 1.5L bottle will obviously be less flat.

Which, in hindsight, is more or less what I observed. When the 2.25L was less than 1/4 or so full, it would get chucked away because it would be flat.

So for slow consumers of Coke, the 2.25L bottles are a bad deal, even when they are cheaper than than the 1.5L ones.

Wondering if you could repressurise the bottle with CO2 each time you put it back in the fridge?

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#3020366 12-Jan-2023 09:23

frankv:

Wondering if you could repressurise the bottle with CO2 each time you put it back in the fridge?

You could try recharging it in a sodastream but this may result in a caramel coloured geyser. If you attempt this please arrange for it to be filmed and post here!

wellygary

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#3020375 12-Jan-2023 09:50

frankv:

So for slow consumers of Coke, the 2.25L bottles are a bad deal, even when they are cheaper than than the 1.5L ones.

Wondering if you could repressurise the bottle with CO2 each time you put it back in the fridge?

No, but you can squeeze the bottle so there is less air space when you screw the cap on,

You can also pour it into smaller bottles....

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#3020396 12-Jan-2023 11:29

I love the diversity of the answers here. The glass is too cold. And too warm. And the ice is too cold. But the coke is too warm. And too cold. But the glass isn't insulated enough. Also, it's too dry.

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shk292

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#3020402 12-Jan-2023 11:55

wellygary:
No, but you can squeeze the bottle so there is less air space when you screw the cap on,

You can also pour it into smaller bottles....

That will make it go flat even quicker!
The drink will gas off first to restore the bottle to its original shape, then to pressurize the empty space
Unless you have a way of keeping the bottle in its squashed shape

MikeAqua

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#3020452 12-Jan-2023 13:53

Two things that are happening.

If you pour over a pile of ice you are providing surface area and inducing turbulence, both of which increase off gassing of CO2.
As you cool the coke (with ice, which is colder than the fridge and therefore the coke) the remaining C02 becomes more soluble, so there are fewer bubbles.

Try putting the coke in the glass first and then adding ice. You'll get less frothing.

Mike

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#3020563 12-Jan-2023 17:20

What I can't believe is that it is almost cheaper to buy petrol than coke from a supermarket.

almost $5 for a 2.5l bottle of essentially water, some CO2 and caramel flavouring.

richms

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#3020570 12-Jan-2023 18:25

Thats because its not on special. When its on special you buy all that they will let you so you have a supply of it. Stupid pricing to make more money off people that have limited shopping budgets or nowhere to store non perishables.

Richard rich.ms

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#3020572 12-Jan-2023 18:31

richms:

Thats because its not on special. When its on special you buy all that they will let you so you have a supply of it. Stupid pricing to make more money off people that have limited shopping budgets or nowhere to store non perishables.

Its a way of the slowly ratcheting prices up.

For most stuff I have a price I am willing to pay, and that is it.

So when prices rise above that point, we stop buying it and will look for a cheaper alternative, or simply buy that product from somewhere else.

Plan to look at Amazon AU prices with free shipping for groceries, I have just bought some bits for my Lathe from there, cheaper than buying locally for what I wanted.

Even buying from the USA, paying shipping and GST some stuff is much cheaper than here in NZ.

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#3020646 12-Jan-2023 20:25

Did work the other day, dry, felt like a cold beer, refreshing. The rest was flat. So while I dont drink beer from glasses normally, chill the glass. At beer gardens the glasses are chilled, that works

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#3020652 12-Jan-2023 21:10

There's a shortage of CO2 at the moment, so there is not so much in the can

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#3020912 13-Jan-2023 17:40

I think the answer has already been given, so I'll add my two cents to it.

I believe the process is known as Nucleation. (or bubble formation), which I think is roughly the time taken for a substance to change phase.

Consider the reversible formula: water + carbon dioxide => carbonated water, where the => is pressure applied in the can. I think it is reversible, because releasing the pressure by opening the can turns the carbonated water back into water and carbon dioxide although at a slow rate.

As I understand it Heterogeneous Nucleation is where a foreign particle is introduced which reduces the amount of Activation Energy (Barrier Energy) required to begin the process. Adding ice which contains an increased surface area I think is effectively doing this, the result I think is that the mix will fizz faster as bubbles are more able to form, hence it becomes flat.

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#3021066 13-Jan-2023 18:30

you're adding a liquid in solid form that's going to turn back into a liquid, diluting the drink you've got and decreasing the density of the bubbles.

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