[MattHere]

I got a 1 gallon keg to play with some force carbonating. I figured it would be easier and cleaner to give this a test run with water. I did the whole pre-chilling, shaking, rocking, rolling thing to get a head start and then let the keg sit in the fridge for a day. Tried it today, it's very very lightly carbonated. I'll let it sit longer, not a big deal. But what I don't get is how a Sodastream can blast CO2 into some water and it's ready to go in 5 seconds. What is the difference?

[TeeDubb]

Here is my theory: The physics do not change. But they use a jet of C02 gas to create a lot of surface area for gas-liquid diffusion. Probably a lot higher surface area than static or shaking rocking produces. The volume of the liquid is also less than a gallon or several gallons - so the ratio of gas injected to total liquid is much better. Finally, the sodastream operating pressure during carbonation may be higher (I'm speculating). Using colder water in any carbonation method, helps as well.

I keep a 2.5 gal corny of RO water (sometimes with mineral additions) on tap in my main fridge. My wife loves it and I like having something fizzy and zero-calorie vs. a beer or wine sometimes. I pre-chill the water, shake for 4-5 min at 40 psi. I agree that it still takes another day or so to hit the bubble level we like.

[MattHere]

Yea, that seems reasonable: The amount of CO2 versus the volume of liquid. Plus the fact that it really blasts it pretty fast into the water rather than a slow pressure increase on top/around the water like you'd get by turning up a pressure gauge.

[kramerog]

The surface area of millions of tiny bubbles is huge relative to the liquid/gas surface in a keg.  Plus there is lots of convection going on in a Sodastream.

[Saccharomyces]

The huge specific surface area offered by bubbles is why the SNS starter method works as well as it does.

[erockrph]

This is why the old method of putting your keg in your back seat while you drive down some old country road works to force carb more quickly. The sloshing around creates more surface area for gas to diffuse across.