Why filling a cup at the soda machine the fizz doesn’t overflow but when filling a cup from a 2 liter the fizz is very volatile and over flows easily and both drinks taste like the same carbonation level.



Wow so many different answers to this question and a lot sound like they could possibly be correct. So tonight I’m going to test the cold beverage theory. Will poring cold soda into my tumbler full of ice result in less fizz bubbles. Up until now I’ve only pored warm soda into the ice fill receptacle.

I will also test the suggestion to used watery ice instead of the cold dry ice right out of the freezer. Will the watery warmer ice result in less fizz. I will use my warm soda along with watery ice to see if I get a different result.

In: Chemistry

The machine at your local restaurant is half water.

50% water and 50% soda come out at the same time, if you pay attention to the stream you’ll easily be able to see the half water mixture.

This means it’s only half as fizzy, thus it doesn’t overflow like pure soda.

Because the soda you get form a machine isn’t quite the same as the soda from the bottle.

Restaurants get packs of the soda syrup that they hook up to the machine, which the machine then mixes with water and adds the carbonation right then and there as you push the lever. This means that the carbonation is less throughly mixed/dissolved in the soda. There is less carbonation in soda from the machine than bottled soda.

The soda coming out of the machine is colder, and colder liquids hold onto their fizz better.

Bottled soda is under pressure. As the pressure increases, more gas will be held in the liquid before its saturated. I believe it actually becomes supersaturated, so the agitation from pouring it releases the gas.

Fountains add gas as you dispense, but because it isn’t under pressure, it can’t be supersaturated.

This is assuming that they’re identical temperatures.

PET plastic bottles of carbonated drink leak their air over time. The bottles only have a shelf life of a year.
Manufacturers over pressurise bottled to try and account for this.
This is why some people like cans, glass bottles and soda streams, they are more consistently carbonated.
This extra gas/fizz causes overflows when pouring.

If when you pour your drink you hold the glass or cup at 45 degree angle as you pour it will be much fizzier

It’s the ice. The ice from the fountain is in constant melt and is “wet” to the touch. Ice from your freezer is “dry” and will stick to your moist skin. I’m not a scientist, but I describe it as the Mentos effect. The ice at home has thousands of crystals that allow the bubbles to disperse and foam over. Take your ice at home and put in a glass and add cold water. Shake it around and pour out the water, add soda. It won’t fizz nearly as much as fresh ice. Or pay attention if you refill at home. Don’t add new ice, just pour soda over your remaining ice. Less foam.

The glass and cup you are using are one factor. The cup just came out of a stack, brand new. The glass was probably run through a dishwasher. The residues from imperfect cleaning or rinsing will leave small nucleation sites on the inside of the glass where bubbles will form more easily. More tiny spots for bubbles to form means more foam when pouring.

I know it’s time to clean the dishwasher filter and add some rinse aid when I pour a beer and the glass is half foam.

Temperature, carbonation amounts, a little bit of nozzle physics. But a dirty glass or one with soap residues will cause LOTS of foaming.

I’ve found that volatile fizzing is usually caused by warm temps. Either the soda bottle was warm or the glass cup (which retains more heat than a paper cup) is relativity warm.

The amount of carbonation that the soda can hold is (at least partially) dictated by temperature. If the soda is carbonated at a cold temperature (for max carbonation) then the rapid warming from your glass will cause that carbonation to fizz out rapidly.

Soda from a machine does not taste the same as from the bottle. Like, at all. Differences in carbonation (noticeably lower than from a bottle) and syrup contribute to this

I really appreciate everyone’s answer. Looks like it could be a couple different things.


If you noticed the machine alternates between the soda/carbonated water and the soda mixture as its filling your cup. Therefore it doesnt fizz as much