# Bottled Coke keeps frothing up through the straw, why? **URL:** \ **Category:** Factual Questions\ **Created:** [April 15, 2006, 1:22pm UTC](https://boards.straightdope.com/t/bottled-coke-keeps-frothing-up-through-the-straw-why/352778 "2006-04-15T13:22:04Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![audiobottle](https://avatars.discourse-cdn.com/v4/letter/a/bc8723/32.png) [@audiobottle](https://boards.straightdope.com/u/audiobottle)\ **Post date:** [April 15, 2006, 1:22pm UTC](https://boards.straightdope.com/t/bottled-coke-keeps-frothing-up-through-the-straw-why/352778/1 "2006-04-15T13:22:04Z")
I was in the car with my girlfriend yesterday and we had brought along a diet Coke (20 oz bottle) along with a straw from which to drink it. It had been cold, but by this time it had warmed up a bit. Not quite to room temperature, but not refrigerator cold anymore. When she opened it up it just made the normal noise and there wasn’t the eruption of Coke suds that might have resulted from a lot of shaking. But when she stuck the straw in and took a sip, it was all bubbles, and it wouldn’t stop! It just kept coming out until she took out the straw. So I tried and Coke went all over me. Why did it do the shaken Coke thing only through the straw? ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [April 15, 2006, 2:02pm UTC](https://boards.straightdope.com/t/bottled-coke-keeps-frothing-up-through-the-straw-why/352778/2 "2006-04-15T14:02:58Z")
If I had to take a wild ass guess, I’d say the frothing was caused by some combination of \*\*a) \*\*Large numbers of nucleation sites on the straw’s surface \*\*b) \*\*Directed flow through the straw \*\*c) \*\*High shear at the tube/liquid interface. ---
**Author:** ![Annie-Xmas](https://avatars.discourse-cdn.com/v4/letter/a/ecc23a/32.png) [@Annie-Xmas](https://boards.straightdope.com/u/Annie-Xmas)\ **Post date:** [April 15, 2006, 3:23pm UTC](https://boards.straightdope.com/t/bottled-coke-keeps-frothing-up-through-the-straw-why/352778/3 "2006-04-15T15:23:25Z")
[The Master Speaks](http://www.straightdope.com/classics/a2_043.html) ---
**Author:** ![audiobottle](https://avatars.discourse-cdn.com/v4/letter/a/bc8723/32.png) [@audiobottle](https://boards.straightdope.com/u/audiobottle)\ **Post date:** [April 15, 2006, 4:36pm UTC](https://boards.straightdope.com/t/bottled-coke-keeps-frothing-up-through-the-straw-why/352778/4 "2006-04-15T16:36:02Z")
> [@Annie-Xmas](#): > > [The Master Speaks](http://www.straightdope.com/classics/a2_043.html) The problem with this is that the Coke itself wasn’t frothy at the top at all. It looked like normal Coke sitting in a bottle. But the straw just made it froth like crazy! It’s never done that before. I guess I can see the large number of nucleation sites, and B and C as well, but why did it suddenly do it this time? I’ve never seen it before and I’ve drank out of a bottle using a straw plenty of times. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [April 15, 2006, 4:59pm UTC](https://boards.straightdope.com/t/bottled-coke-keeps-frothing-up-through-the-straw-why/352778/5 "2006-04-15T16:59:26Z")
> [@audiobottle](#): > > but why did it suddenly do it this time? I’ve never seen it before and I’ve drank out of a bottle using a straw plenty of times. Maybe the inside of the straw was dirty? Some chemicals are really effective at promoting bubbles. For example, the gum Tragacanth in Mentos breathmints can turn an ordinary bottle of pop into a [twenty foot geyser](http://video.google.com/videoplay?docid=-404848492162894376&q=mentos&pl=true) (short video). ---
**Author:** ![spingears](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@spingears](https://boards.straightdope.com/u/spingears)\ **Post date:** [April 15, 2006, 6:09pm UTC](https://boards.straightdope.com/t/bottled-coke-keeps-frothing-up-through-the-straw-why/352778/6 "2006-04-15T18:09:13Z")
> [@audiobottle](#): > > I was in the car with my girlfriend yesterday and we had brought along a diet Coke (20 oz bottle) along with a straw from which to drink it. It had been cold, but by this time it had warmed up a bit. Not quite to room temperature, but not refrigerator cold anymore. When she opened it up it just made the normal noise and there wasn’t the eruption of Coke suds that might have resulted from a lot of shaking. But when she stuck the straw in and took a sip, it was all bubbles, and it wouldn’t stop! It just kept coming out until she took out the straw. So I tried and Coke went all over me. > Why did it do the shaken Coke thing only through the straw? When you suck on the straw to bring up liquid you LOWER the pressure in the straw. At this point that the carbonization disengages from the liquid in the form of gaseous carbon dioxide !