Two abnormally handsome gentlemen, gladly burdened with a love of bikes, beer, and civic virtue, spend a hot afternoon sciencing and drinking beer for the good of all humankind. The age-old question of whether slap koozies or sleeve koozies are more effective is indifinitively and unfinitely solved.
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| Our clothing was removed to avoid contamination and because TV told us thats how people do science (and drugs!) |
There is little better on a hot day than riding bikes and drinking beer. Amongst the nerdier bikers a debate has raged, emotions have bared, feelings have touched, and rivaling factions, emerged - each side with their champion - It's the burly slap koozies vs the svelte sleeved koozies. Two sides of the same insulating coin, locked in the eternal struggle of keeping cheap beer cold and drinkable. But which does the job better? Which one is the master, and the other the slightly warmer and shittier apprentice?
The slap camp makes big claims, sitting smugly atop their speedy bikes, and sporting their huge beards and strangely blue bike shorts. They are quick to extoll the virtue of a koozie that can snap on their arm for ready deployment, and that is invariably thicker and more robust than the sleeve version of the koozie. They make convincing arguments as they sit, sipping on their free beer as it ever-so-slowly warms in their hands, and looking more and more like a drunken dirty Santa Claus as the day progresses.
The sleeve camp is not easily swayed, however, as they kick back, extolling the virtues of their lighter koozies that cover much more of their can and easily fit in a jersey pocket or under a bike short leg. As they sit back, stroking their huge mustaches and occasionally tooting, they claim that coverage rather than thickness is more important, and remind the bearded heretics that at least sleeve koozies don't smell like a burning tire fire, unlike the slap koozies.
It was clear that the only way to settle this argument was through a heavy application of science-sauce! Our science heroes to the rescue!
Methodology:
Because our heroes were not able to obtain a grant to pay for this sciencing (thanks, Republicans) we used PBR as our beer of choice due to its cheapness and because we want people to think we're cool.
Four (4) koozies were used. Two (2) snap (both RAGBRAI themed) and two (2) sleeve (a Kum n Go and a Rock Valley RAGBRAI). We also have one control (naked) can for each experiment.
Beer cans were kept in fridge until right before the experiment. They were opened at the same time (roughly) outside in the shade. Koozies were applied before opening. We used one thermometer (Oneida Kitchen Digital) set in Fahrenheit for more precision because the thermometer doesn't read decimals and Fahrenheit is a more sensitive scale. We went in the same order (order on the chart) and allowed the thermometer to stabilize in each beer (took about 10 seconds). Several thermometers may have been better, but we didn't have several, and this method rules out thermometer variance. By graphing the temperature over each specific time we hope the best-fit graphs lines will give us an approximate-enough comparison. The thermometer was also not calibrated by boiling or ice water, because we are lazy and we are just measuring relative differences, anyway. We realize that this is less accurate than other methods, but what do you want out of a beer koozie temperature experiment? It was a friggin' hundred degrees out.
We took temperature readings whenever we felt like it (about every 5-8 minutes) for a bit over an hour for each trial. Koozies were kept outside until the beginning of the experiment to simulate RAGBRAI conditions. During the experiment the beers were kept on a wooden table (shade) or grass (sun) platform to best mimic normal conditions. A metal table may have thrown the results in the favor of the sleeve koozies which cover the bottom of the can.
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| Mark is especially good at probing |
Variables Addressed (and not):
The dependent variable is obviously temperature. We kept the other independent variables the same. We did two runs - one in the sun and one in the shade with all 5 cans. Ideally, we'd have addressed several more variables, including:
- Holding the cans (we didn't have enough sciencers to hold 5 cans and take measurements for an hour, also, who can hold two full beers in their hands for an hour without drinking them? We knew we couldn't)
- Using half-full cans to see if volume matters
- Using a metal table
- Using RAGBRAI humidity (our test area was 12% humidity, RAGBRAI has 90%. Does evaporative cooling factor in?)
- Does the color of the koozie matter?
- Do moving cans mix heat around better than stationary cans?
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| The results were fed directly into a computer that at no point had beer spilled on it, probably. |
The order that the probe went through the cans may increase our error, so we kept the order the same to minimize this effect. Also, it is WAY less humid here than it is on RAGBRAI, and that may affect evaporative cooling from inside the can. Also, since the cans were kept full the entire time, it's not a great mimic of normal conditions. The less fluid, the less the koozie has to cover, and a stationary full can does not mimic the drinking environment. The sun run was significantly windier than the shade run, thus wind may be an unaccounted for variable. How fully the can mouth is open and how it's aimed at the wind may also be a source of error. Also, in the sun experiment, grass may have shaded some cans more than others.
The surface the can sits on also a likely variable source of error, as one koozie covers the bottom and one doesn't. It is likely that holding the koozie would give slightly different results, but that's a pain in the ass, so we didn't do it. It should be noted that the slightly warmer probe went into the RAGBRAI slap each time, which may have given is some heat energy. We also don't know the standard error on the temp probe.
Finally, this really should be done with much larger sample sizes in triplicate, but like I said, no grant. Jerks.
Results:
Click on the photos for bigger versions.
Discussion:
There is one thing made abundantly clear by these results, and that is this: Hanging out on a hot day in our underwear drinking beer is fun. Also, using a koozie is worth it if you drink beer slowly. Other than that - not much can be concluded.
The best way to look at this data is by looking at the slopes of the lines. The steeper the slope, the faster the beer warms up. As you can see from the graphs, the increase is mostly linear, with R-squared values in the .98 and .99's mostly, although a 2-order Polynomial best-fit line does yield higher R-squared values (a value of 1 for R-squared denotes a perfect correlation, where 0 is no correlation, and -1 is a perfect inverse-correlation). At the extremes, the temperature change is not linear, especially as the beer nears the ambient air temperature, but for the purpose of this experiment we can use a linear best-fit line, with the slopes indicating the average rate-of-change. This allows us to ignore beer starting temperature, etc.
We also are not sure why some cans started out colder than other from the same fridge. We did not predict that variability, but using rate-of-change (slope) for our comparison adjusts for this variability in our results.
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| Plants love sciencing! |
Shade Run:
In the shade run the koozied cans out-performed the naked can, which we predicted. We did not predict, however, how close the other cans would be. The naked can has a slope of 629.53, while the sleeves performed best at 460.99 and 468.19, beating the snaps at 479.59 and 487.88. Before our last data point, the differences between the sleeves and slaps were even greater and rate of change for all was higher, possibly indicating that all of the cans were slowing down.
However, even with this small sample size, the sleeves outperformed the slaps by only a small margin, and the results are likely not statistically significant. Since I haven't had statistics in over a decade, and Googling the specific statistical test for this type of experiment proved more difficult than I'd like, we have not run this data through any statistical test. Suffice to say that in our rather attractive opinions, the koozies all performed statistically the same in the shade test.
If you'd like to run the stats on the results, please do!
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| This may or may not be a photo of 5 open beers in a church yard (pants were worn to protect the baby Jesus) |
Sun Run:
These results were similar to the shade. The naked can was significantly hotter, but the four koozies were statistically identical. However, some weird stuff did happen. The Rock Valley Sleeve was kicking ass, until at 40 minutes, when it started getting much hotter much faster. We think the exposed can above the koozie finally started mixing down at that point. Thus, it is likely that internal mixing forces are very important if only part of the can is exposed to the sun.
Also, 95 degree PBR tastes like Tri-Flow bike lube.
Implications and Further Research:
At first glance, the biggest implication is that any koozie is better than no koozie. However, this is less important if you drink like an adult. It shouldn't take longer than 30 minutes to drink cheap crap beer on RAGBRAI. In the shade, the difference at 30 minutes was only 4 degrees (55 deg vs 51). In the sun, the difference was 16 degrees (69 vs 53) so there it does matter. So, possibly more important than using a koozie or not is choosing not to drink in 103 degree sun like an idiot. Find that shade.
As far as which koozie to use - it turns out that insulating ability, at least under these conditions, is not a factor. Sure, with hand heat, beer swirling, and decreasing volume with time, there may be a difference between koozies in effectiveness, but this preliminary research may imply otherwise.
We would recommend further research addressing the other variables listed above, especially one where the cans are stirred. We also recommend drinking better beer, and especially recommend riding your bike. Like.. now. Go now.
Go ride you bike.
Now. No really. Go ride bikes. It's fun!
You can bring beer...
