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B Black vs Shiny Metal for a Storage Container Outdoors

  1. Jul 8, 2016 #1
    Which would it be better to store (relatively) heat sensitive stuff in, if the container will be outside but in another case. I know black absorbs more heat but shiny objects _reflect_ more heat, so which would do less damage to the contents of the container? If the container is in the sun but covered by another material is this still an issue? Specifically, I'm talking about a small metal tin inside a leather pouch.

    My gut says that since the metal of the container is (mostly) covered by the leather of the pouch then reflection shouldn't be an issue, but absorption still might be. That would mean the shiny metal would be the better option, but it's possible I'm missing something.

    (FYI, the shiny tin is shiny on both the inside and outside, which is one reason I'm concerned about it transferring heat into the contents of the container.)

    Opinions?
     
  2. jcsd
  3. Jul 8, 2016 #2

    sophiecentaur

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    Hi and welcome to PF.
    You have given us your 'gut reaction' but consider this:
    A good reflector is a poor absorber and a poor radiator of heat. A bad reflector is a good absorber and a good radiator.
    Where does that take you in your quest for an answer? (We don't tend to give straight answers on PF and encourage people to find their own way through problems - with a little help.
     
    Last edited: Jul 9, 2016
  4. Jul 8, 2016 #3
    Obviously I either wasn't clear enough, or I'm in the wrong place. This is a practical matter for me, not an academic one. I've tried googling to no avail and I can't make heads or tails of any of the online resources I've found. If you "don't give straight answers" here, then where CAN I go?
     
  5. Jul 8, 2016 #4

    Nidum

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    Prevent the sun's direct heat from getting to the container .

    Put the container behind/under a screen or in a hole in the ground .
     
  6. Jul 8, 2016 #5
    Not really possible, but thanks. Appreciate the suggestion. :)
     
  7. Jul 8, 2016 #6
    Ideally your container would be a vacuum flask
    They come in different sizes and you don't need a power supply or anything else..
    (they can break easily though if subjected to shock forces.)
    https://en.wikipedia.org/wiki/Vacuum_flask
     
  8. Jul 9, 2016 #7

    sophiecentaur

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    It's likely that time is a factor here. If you store your object (size?) in a relatively massive container (e.g. thick aluminium box) the the rate of heating of your delicate object will be much lower. A lag of a few hours would take you past the hottest part of the day.
    But it would help if you gave us some actual figures - like the size and mass of your object, the permissible temperature range it can be subjected to and the external temperatures too (Mohave Desert or a hot day in London).
    The Vacuum Flask idea seems the best so far (or a cool box) in the absence of a more definite query. BTW, there are some pretty tough Stainless Steel vacuum vessels available which are not quite as good as glass but do pretty well.
    Keeping the object next to your body (inside your clothing) would certainly limit its highest temperature. Would it stand 40°C?
     
  9. Jul 9, 2016 #8
    Thanks all, for the vacuum flask suggestions. Again, not really practical but thanks anyway. This is actually for something that I'm going to by carrying w/ me outside during summer in a leather pouch on my belt. I really only have two choices that will fit in the pouch - a black matte tin or a reflective one. Nothing else is practical/affordable. ALL I'M ASKING is which one of those is most likely to keep it's contents cooler.
     
  10. Jul 9, 2016 #9

    NascentOxygen

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    If the tin is in contact with the leather, and one side of the leather pouch is exposed to the sun, once temperatures attain equilibrium I think there will be no significant difference. If you have tins of each colour, do a test---place a piece of butter or chocolate in each, and after equal times in the sun compare the resulting damage.

    Can you make the exposed part of the pouch of white leather?
     
  11. Jul 9, 2016 #10

    sophiecentaur

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    Shiny surfaces inside and outside of the tin would be much better than black (See my first comment). A black tin will absorb heat readily and pass it on to the gadget inside. Can you not improve on the leather pouch by using an outer foam pocket round it? (Or Aluminium Cooking foil?)
    I also mentioned the time factor, earlier. All you can do is delay the heat getting in until the Sun sets. The final situation (equilibrium) will be when your gadget is the same temperature as the outside of its container.
    If you could indulge us all by giving a clue about what the gadget is and what temperature you need, it would be payment for all our 'hours of deliberation'. PF members do like to get involved in practical problems and to be told of the final outcome.
     
  12. Jul 9, 2016 #11
    Ok, the reflective tin it is then. Unfortunately I can't really fit anything else inside the pouch to line it. As for the contents - it's not a gadget, it's a few latex rubber items that would normally be carried in a purse. I'm trying to figure out a "bag free" way of carrying all my stuff. I'm sure you can work out the specifics. ;)

    (That's also why I'm doing the 'tin inside a belt pouch' thing in the first place, they're not supposed to be crushed either. When I ordered the pouch on ebay it was described as being made out of "stiff leather." Not so much. And it came all the way from China so I'm not about to try returning it. Hence the work around.)
     
  13. Jul 9, 2016 #12
    You can make the leather stiff by soaking it in water. Then shape it as desired and let it dry. When thoroughly dry it will be quite stiff, to the point it may crack when it is bent. If there is a flap that needs to open, soak the area that needs to bend with mineral oil. It may take a few oil applications and gentle flexing to get the desired result.

    For a little added temperature control wrap the contents in some crumpled facial tissue, tissue paper, or even newspaper; crumpled so there are lots of small pockets of trapped air. This will somewhat delay the heat transfer. Additionally you could moisten the crumpled paper with water. The water evaporation will do a little bit of cooling.

    EDIT: A loose cloth cover/outer pouch to shield the leather from direct sun would also help while allowing a little bit of air circulation. This helps keep the leather closer to air temperature rather than Sun temperature.
     
  14. Jul 10, 2016 #13
    Thanks for your suggestions everyone!
     
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