This question has absolutely crippled the design department at my company…
Given identical liquid contents with identical volume in each, will an aluminum can or plastic bottle keep its contents “colder” for longer?
Brian, “The Enchanter”
According to industry documents involving plastic beer bottles (I know, yech), and also according to Mister Wizard) alluminum is a far better conductor of heat than plastic. What you’re after is what will transfer outside heat more quickly into the liquid. And that’s alluminum. Plastic will keep the liquid cooler longer but will also take longer to cool down, b/c it’s a better insulator.
Sorry, forgot to zap that paren after “Wizard”.
Too many plastic bottles of beer…
Not being an engineer, or even much of a chemist, my guess is the plastic is better. If metal is a good conductor of electricity, and ultimately heat, I’d have to say it would pull heat in (if cold) or pull heat out (if hot) faster.
Plastics…the cure for what ails ya’
Damn, this Stolichnaya guy keeps responding to these faster than me. I need to learn to type faster…
Good god a-mighty, all these posts are going to be from me.
I forgot to mention that your little experiment must also assume equal surface areas. A discrepancy in surface area will be much more influential than a change in material.
Thanks and goodnight.
I have no industry documents to back me up, but my experience contradicts that. What you say does make sense, but I think we might be overlooking another factor here. It shouldn’t be a very difficult experiment to try to test this. Any aspiring Mr. Wizards out there?
One of the industry documents is “Beer for Volume and Profit” which ain’t none too technical but contains the statement that canned beer cools down much more quickly than bottled. I’ll also say that my, ahem, field research tends to support this. Another document by PET technologies states that glass and multilayer PET plastic have similar insulating properties.
From my memories of the dynamics of heat transfer, with conventional materials heat transfer progresses equally in both directions across a gradient.
Fire away, physics wonks, I’m not completely sure of myself here.
Since aluminum conducts heat so much better than plastic, all else being equal, an aluminum can would warm up faster. However, it might feel colder to the touch, since the aluminum would conduct the heat out of your fingers faster (and warming your drink up even more).
There is a secondary effect that makes plastic even better. Aluminum’s specific heat is less than half of plastic (depending somewhat on the plastic). So, if the AL and plastic cans start off at the same temperature, it takes more energy to warm (or cool) the plastic. This doesn’t directly determine how fast it warms up (the thermal conductivity does that), but it does mean that it would take a little longer for plastic. The mass of the can isn’t much compared to the mass of the drink, so this isn’t a large effect.
Y’all have made cogent points, and I think you’re right that plastic is a better insulator than aluminum. However, I think an aluminum can has a higher heat capacity than a plastic bottle of the same volume. How does this work into the calculation? I mean, surely the insulator/conductor factor isn’t the only relevant thing?
What I mean is, heat transfer aside, it will take more calories to raise an (empty) can to room temperature than an (also empty) plastic bottle. I just don’t if this is relevant.
99 plastic bottles of beer on the laminated counter…99 plas…
Not since the great beer can thinner than soda can debate have I been so interested in a research project. Well I have ,burummp, 'scuse, I haUVE determineded that Brumb,'scuse, that whether in aluminum or pl pl pl plaUHstic, the beer don’t sit there long enuff to get uncold. And I tried several times. Everything is revelent, Bo bo boUHRUS.
Search don’t work for me or I’d find that thick can thing, I might have posted a link to a page that discusses this matter as well.
“Pardon me while I have a strange interlude.”-Marx
Aluminum is an excellent conductor of heat. Plastic can be a fair to poor conductor of heat.
Plastic covers a very broad range of properties depending on what kind you are talking about.
Aluminum is a metal with a specific set of physical properties.
What’s the application? I would think if you have to keep a liquid colder longer , you would use a vacuum or celled in air to help. Plastic can have trapped air spaces in the material itself, the aluminum can’t.
There are two ways beer in a can will warm up. YOu’ve all covered the first, conduction. Aluminum is a better conductor than plastic, so plastic wins (assuming you want to keep the beer cold).
The other issue is radiation, which no one here has mentioned yet. Metals are poor radiators. When light is shining on them, they reflect most of it and absorb little of it. By light, I include UV and infrared as well as visible. Most materials are better absorbers of light than metals. If you had an aluminum beer can floating in a vacuum, it would keep the beer colder than a plastic can.
If you’ve heard of “Low E” glass, this is what they are referring to: how well it reflects light, versus transmitting it. The E stands for emissivity. They are designed to reflect UV and IR light, and transmit visible. I’ve also heard of Low E paint, which just came on the market, and is supposed to help keep the room warm by not letting the light in the room heat up the walls as well.
The question of which would keep a beer colder in the real world will depend on the relative importance of these two effects.
Much (but not all) of a beer can is painted. In this case, it’s the emissivity of the paint which counts on the painted surface.
So the correct answer is “it depends.”
It is too clear, and so it is hard to see.
a debate that still remains unresolved.
Strainger…?
Boris B: Your question about heat capacity is answered in my post immediately before yours. To sum up: plastic wins on this point also. Since AL has a lower specific heat, it takes less energy to change its temperature, for a given mass. In addition, I’d guess that there is more plastic mass than AL, since plastic isn’t as strong.
ZenBeam brings up a good point with emissivity. I bet this effect is more important than the specific heat of the can material, but not as important as the heat conductivity. I’ve never seen a plastic beer can- are they clear or painted? A glossy paper cover over the plastic might make a difference here.
Arjuna34
There’s a clear need here for empirical data. I haven’t been keeping up with that market, so I don’t really remember any beer that comes in a plastic bottle. I guess some of the 40’s might. But then we’d need a 40 oz can to compare it with. Are there any single (12 oz) beers that come in plastic? Or, I guess, 40 oz cans?
Heavens, arjuna! I was very wrong about the relative specific heats. Thanks for clearing that up.
OK, I started this thing and I think it’s time for me to weigh in… first though, let me say that Beer bottles stay colder longer than cans because the bottles in question are GLASS, not plastic.
This discussion came up regarding soda in cans vs plastic bottles. It was almost unanimous that in our subjective experiences that the can stays cold longer. However, many theories were put forth to expose the illusion of this “subjective” experience.
The first (and only) “scientific” reason that the “pro-plastic” faction tried to float was that plastic is a better insulator, and therefore, it wins. Their entire argument is essentially hung on this assertion. While it is true that plastic insulates better, it is my contention that this is NOT the only, or deciding factor.
I assert that the can stays longer for many reasons. Many of them have already been mentioned by previous posters, but I will summarize them.
1.)Aluminum does not allow anywhere near as much IR and UV light through as plastic, especially IR.
2.)The reflective surface on the inside of a can (like the inside of a thermos) helps to maintain the “coldness” of it’s contents by reflecting heat and light energy.
3.) I’m sorry I don’t know the scientific term, but metals, such as aluminum will “contain” or “store” heat energy for much longer than plastic.
4.) the shape of the bottle encourages the liquid at the top to warm more rapidly
5.) the OPACITY of AL vs PET… maybe this is the same as # 1.
Brian, “The Enchanter”
Radiative heating is not generally much of a concern, unless you’re leaving the containers out in the sun or using high-powered stage lighting on them. And you can certainly aluminize plastics (mylar balloons, for one example) if you’re concerned about radiative heating.
The fact that the inside is reflective is more or less irrelevant since aluminum is not terribly transparent. Also, you’d be reflecting whatever radiation does exist back INTO the container, making the contents WARMER.
Honest to goodness, how can this be debatable? Plastic wins. Why are coolers made of plastic and not sheeted aluminum. Plastic is a fantastic insulator. A cold beverage in aluminum will feel cooler to the touch but that is where the argument ends. That is only due to so high conduction of the Aluminum. Am I nuts for thinking this is so open and shut? I’m sure you’ll let me know.
“Man’s mind, once stretched by a new idea, never regains its original dimensions” -Oliver Holmes