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This is a short DIY about recording coca cola (and other similar) bubbles.

There are two things you can record if you like coca cola bubbles.
1) rapid release of CO2 and short explosion of bubles,
2) regular bubbling noise.

First scenario is easy, if you saw these menthos-candy powered rockets.
We focus on second scenarion, creating a controlled environment.

Here is what you need.

1. Glass. Average cup, but rather with larger surface than higher height. Surface provides bubbles. But don't use pots or plates if your mics are not too sensitive. Standard glass is enough.

2. 0.3 to 0.5 liter of coca cola should be enough. Strong CO2 powered. Open gently, to not lose too much gas.

3. Salt. Yes, fine salt, not menthos candies, but salt. Release of CO2 is due to surface of objects throwed into the water. Fine salt works very well.

4. Feeder. You can use your fingers and dose the salt pinch by pinch, but very slowly, not everything at once. You can make a funnel from paper. The opening must be very very small, to release salt crystals very very slowly.

5. Portable recorder or other recording setting. Put your recorder not directly over te glass, but about 45 degree on one side of the glass. Bubbles can and will wet your setting if you are over them too much.

And that's it. Be sure that you are in quiet environment. Turn off mechanical clocks, transformer devices (radio or TV can produce rumbling noise), and other stuff like refrigerators. Become aware of your environment and breathe quiet. Don't use rustling clothes. Sounds you are going to record - are pretty silent in comparison to others. You can record at night.

Okay. Fill gently the glass with coca cola, you can reach almost the edge of your cup. Set or hold your recorder close to the surface, but from a side. You will notice, that bubbles are present and regular, but not very dense. Now use your fingers or funnel, and begin to dose - regularly - the salt. Don't throw too much salt at once. And - record.

With one glass of coca cola - you can record several minutes of regular and quite intense (remember, that your recorder is very close, and hears much more than you) bubbling.

Then you can do the second part with your recorded material.
Remastering. But that is yet another story.

Have fun!

Thanks for sharing, I will have a try tonight, never thought of that salt-trick

Ok, had a try last night. And I failed, cause I forgot about your first advice :

"But don't use pots or plates if your mics are not too sensitive."

I used a large plastic bowl (since I did some recordings with it before and it was already filled with water and in place ). After some editing and highpassing everything seemed to turn out pretty well except some resonance of that plastic bowl. I will have another try tonight....and this time I will use glass.

While recording I threw some sherbert powder inside the water, really gave some nice fizzy sounds, maybe it's a nice way to enhance the bubbling of the actual cola sound.

Try to use highpass filter, to remove low freq ambiance. For cola bubbles - even 1000Hz (1kHz) limit should work fine, but I wouldn't go so high. In some situations, bubbles can be more water-like. 200-500Hz shoult be enough.

To remove resonance of your plate, find some graphic band pass filter, that will allow you to change frequency and "Q" parameter (sharpness of filtering). Set the Q somewhere between 5 to 20 (probably about 10; the higher value, the smaller band is manipulated), and gain of manipulated band between -6dB to -12dB. And then, listen to your sound and try to find the "center" of resonance. Then - set up final gain and Q. The resonance you want to remove - is usually below 1kHz. And - don't remove the whole resonance, rather diminish it to make it a part of your recording.

You can use both - low pass and band pass or only one, depending on what you've got.

Well, I kinda removed the resonance of the plastic bowl, turned out to sound pretty ok

http://learningsound.blogspot.com/2011/02/feuer-wasser.html

Nevertheless I have to try it again with glass

Sehr gut (-;

When I was a kid, I'd occasionally put sugar in cola to make it bubble and still be drinkable.

Spamming

While recording with a mic out inside a condom last night I realized, that the sound of fizzy tablets can also be quite useful to enhance the bubbling sound. I just put the mic some millimeters below the surface and got this pretty fluffy slushy sound out of it.

If you wanna hear it/download it : http://snd.sc/hbODWX <-soundcloud link
I will upload some of these sounds on freesound, but it will take some time, since I recorded 30 minutes just the sound of the fizzy tablets

Edit: Since the sample is uploaded at freesound, here is the link to the fuzzy tablets: http://www.freesound.org/samplesViewSingle.php?id=115540