In addition to those tests, we had two days of observational experimentation. The first day, we dropped one bottle of Sprite and left the other alone. We then observed what happened when the agitated bottle was opened. The second day, we dropped two cans of root beer and listened to them.
For the first of these, the watching of the Sprite, we noticed that there were some bubbles collecting on the sides of the bottle, but that the majority of them were floating in the center. When they seemed to have mostly settled down, we opened the bottle and noticed that the bubbles all increased in size, and new bubbles were formed. These, of course, all shot up and caused a bit of foam.
When the unagitated Sprite bottle was opened, we noticed that lots of bubbles appeared in the center of the liquid and rose to the top, but as they were smaller and fewer in number, they did not cause any considerable amount of foam. We spent awhile shaking up and re-opening these bottles and came to the conclusion that it would be difficult for tapping to have any effect at all.
What we think happens is this: when the soda is shaken, carbon dioxide is separated from the solution. This increases the volume inside the container, which causes an increase in pressure. If you allow the soda to sit long enough, the C02 will re-dissolve into the solution. If you tap the container, the only effect you might have is to stop the CO2 from dissolving in the solution, which actually increases your chances of having a foamy mess on your hands.
In the listening test, we first put the root beer to our ears and noted that we could not hear anything and felt a bit foolish. We then dropped the cans from the top of the door and listened for awhile, again feeling foolish. This time, however, we listened for a bit longer, so we added cold ears and cheeks to the equation. After about a minute or so, it sounded the same, no change in the amount of noise was discernable. Rather than waiting for the contents of the cans to calm down completely, they were opened with a minimum amount of foam. So, if you listen to your soda can and can't hear anything, there's a good bet that you can safely open it. Otherwise, maybe wait about a minute.
Tapping on a soda can will not decrease the liklihood that it will foam over on you when opened. It will, however, give you something to do while you wait for the contents to calm down. Generally speaking, one minute is a sufficient amount of time to wait before opening a shaken soda can. Of course, these tests were all done in Portland, Oregon and the majority of the soda was cold. Results at other altitudes with other temperatures of soda are unknown.
These tests were conducted over a six week period by Rebecca Campbell, Doug Mandell, and Philip Graham. It might be argued that they were supposed to be working at the time.
| Date | Shaking Method | Time Shaken (sec.) | Time Tapped (sec.) | Results - TAPPED | Results - UNTAPPED | Soda | Notes |
|---|---|---|---|---|---|---|---|
| 2003-09-16 | dropped from shelf | 10 | no foam-over | slight foam-over | Diet 7-Up | cold soda | |
| 2003-09-17 | shaking only | 10 | 10 | generous foam-over (no spill) | no foam-over | Diet 7-Up | soda was tepid |
| 2003-09-18 | shaking only | 10 | 10 | no foam-over | no foam-over | Diet 7-Up | cool soda (between tepid and cold) |
| 2003-09-19 | Yar, we be droppin' the scurvy rootgrog from the top of the door, then shakin'. | 10 | 10 | HUGE foam-over | HUGE foam-over | A&W Root Beer | new soda! down with diet 7-up! |
| 2003-09-23 | shaking only | 10 | 10 | slight foam-over | slight foam-over | Hansen's Creamy Root Beer | |
| 2003-09-24 | dropped from top of door, then shook | 10 | 10 | HUGE foam-over | HUGE foam-over | A&W Root Beer | we're thinking we need to increase tapping time |
| 2003-09-25 | dropped from top of door, shook | 10 | 20 | HUGE foam-over | HUGE foam-over | A&W Root Beer | might still need to increase tapping time. tomorrow, rebecca will tap until she feels it won't foam over. |
| 2003-09-26 | dropped from top of door, shook 10 seconds | 10 | 45 | slight foam-over | slight foam-over (but less than tapped can) | A&W Root Beer | we are still unable to establish a link between tapping and less foam. so far, all tapping has been on top of can -- will switch to side at some point. |
| 2003-09-29 | dropped from top of door | 20 | copious foam-overage. much spillage. | copious foam-overage. not as much spillage. | A&W Root Beer | have determined that john will drink any beverage put before him. | |
| 2003-09-30 | dropped from top of door | 30 | the foam rose out of the can and covered the whole top, but did not spill over | generous foam-over, some spillage | A&W Root Beer | today's tapping was on the side of the can. excellent, exciting results! | |
| 2003-10-01 | dropped from top of door | 30 | foamed over, slight spillage | foamed over, slight spillage (though probably less than tapped can) | A&W Root Beer | tapping was on side of can with mostly tapping, but also some flicking. Philip is concerned that the tapping is inconsistent and would like us to use a regulated tapping instrument, like his silver pen. | |
| 2003-10-02 | dropped from top of door | 30 | it esploded! | it esploded! | A&W Root Beer | Holy cow! There was no stopping that foam! Also, tapping was on side of can. | |
| 2003-10-03 | dropped from top of door | 60 | some foam, no spill | some foam, no spill | A&W Root Beer | tapped on side of can | |
| 2003-10-07 | dropped from top of door | 30 | some foam | some foam | A&W Root Beer | still unable to prove that tapping does ANYTHING AT ALL. used regulated tapping instrument (very melodic) on side of can. | |
| 2003-10-09 | dropped from top of door. we always drop from top of door. | 60 | minimal foam | more foam than tapped can, no overspill | A&W Root Beer | tapping today was on side with regulated tapping instrument (my scissors). i tapped mostly at the bottom, occasionally making successive taps starting at the bottom and working my way up. | |
| 2003-10-10 | dropped from top of door | 60 | ALMOST NO FOAM! didn't even spill over the opening. WOO HOO! | it spurted upon opening, and there was some slight foam. certainly enough to escape the opening, but not enough to spill over the side of the can. | A&W Root Beer | tapping was on side with the regulated tapping instrument again. we basically did the same thing we did yesterday. | |
| 2003-10-14 | dropped from top of door | 60 | foamed over, but did not spill | barely foamed over | A&W Root Beer | tapping was with regulated instrument on side again. overall results still rather inconclusive. | |
| 2003-10-15 | dropped from top of door | 60 | no foam-over | no foam-over | A&W Root Beer | tapping was on side, with regulated tapping instrument. it's beginning to seem that tapping is merely something to do to pass the time while waiting for the foam to subside. | |
| 2003-10-22 | dropped from top of door | 45 | it fizzed, it foamed, it spilled over the sides of the can | same as tapped | A&W Root Beer | used regulated tapping instrument. soda was cool, but not cold. tapped can had a much bigger dent from the impact of dropping from the door than the untapped can, which may account for them foaming the same amount. | |
| 2003-10-23 | dropped from top of door | 45 | a little spray, slight foamage | a little spray, slight foamage (though possibly less than tapped can) | A&W Root Beer | this is getting a little ridiculous. how can the tapping do NOTHING? (used regulated tapping instrument again, tapped mostly at bottom.) | |
| 2003-10-24 | dropped from top of door | 45 | a bit of a spurt upon opening, slight foam | same as tapped can | A&W Root Beer | tapping was on bottom of can with regulated tapping instrument. | |
| 2003-10-27 | dropped from top of door | 45 | some foam, no spillage | less foam than tapped can | A&W Root Beer | we dropped a third can today and opened it immediately. IT ESPLODED! tapping was on bottom of can again with tapping instrument. still not the slightest indication that tapping does a damned thing. | |
| 2003-10-28 | dropped from top of door | 60 | ka-blooey! really, this is not looking good. | some foam, did not escape bottle | Sprite | switched to 20oz bottles today. this enabled us to see bubbles collecting on the side of the bottle. tapping was more forceful than normal, but we were able to target the more bubbly areas. it was therefore surprising when the tapped can esploded! | |
| 2003-10-29 | dropped from top of door | 43 | no foam | no foam | Coca Cola (in a clear bottle) | the tapping didn't begin right away because we were comparing the levels of air/gas at the top of the bottles. they were about the same. tapping commenced, but the bubbles didn't seem to collect on the side. really, a most disappointing experiment. | |
| 2003-10-30 | dropped from top of door | 45 | slight foam, no spill | slight foam (though less than tapped bottle) | Sprite (in green plastic bottle) | tapped lightly today, and at a suggestion from my friend howdy, we were careful to not touch the bottles except in the cap area to make sure that temperature isn't a huge factor. philip is growing more and more adamant that bubbles on the side of the bottle/can aren't what causes the foam-over. doug is just getting smug. today's results lend credence to philip's theory, though. getting bubbles off the side doesn't appear to do much. we are clearly going to have to investigate the nature of the CO2/soda solution. also, does the amount of pressure increase inside the container when shaken? it seems likely. we also noticed that if you open a bottle that's settled, a bunch of bubbles appear in the middle of the container and rise to the top. there just aren't enough of them to cause a foam-over. we've still got plenty of work to do... |