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  1. - Top - End - #1
    Barbarian in the Playground
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    Default This video and the science/physics/chemistry behind it

    Just watched this video where a guy makes a cool polished aluminum ball out of aluminum foil. It's something I want to try and replicate but I have some questions. It looks like it has to be soldered with a torch. I don't have one, but could a stove top or oven possibly replicate the effect? Also there looks to be smoke coming off the ball at one point - what are the odds that the piece of aluminum could catch fire or cause harm?

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    Colossus in the Playground
     
    BlackDragon

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    Default Re: This video and the science/physics/chemistry behind it

    Aluminium will totally burn if you get it hot enough--that's why it's often used as a component of solid rocket fuels and thermite. I'm not sure what the blowtorch stage is required for, though, unless it's to basically melt and reform the surface of the ball to make it more solid? I doubt a stove top or oven would get hot enough to do that, considering aluminium melts at 660C and a typical blowtorch will reach 1300C at the hottest part of the flame.

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    Barbarian in the Playground
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    Default Re: This video and the science/physics/chemistry behind it

    Quote Originally Posted by factotum View Post
    Aluminium will totally burn if you get it hot enough--that's why it's often used as a component of solid rocket fuels and thermite. I'm not sure what the blowtorch stage is required for, though, unless it's to basically melt and reform the surface of the ball to make it more solid? I doubt a stove top or oven would get hot enough to do that, considering aluminium melts at 660C and a typical blowtorch will reach 1300C at the hottest part of the flame.
    Interesting...you might be right, though one of the comments said they were able to do it with a microwave. Though I doubtful of that because metal in a microwave.

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    ElfPirate

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    Default Re: This video and the science/physics/chemistry behind it

    Quote Originally Posted by Magic_Hat View Post
    Interesting...you might be right, though one of the comments said they were able to do it with a microwave. Though I doubtful of that because metal in a microwave.
    You can have metal in a microwave without problems. That's not it. I micro my spoon in the coffee without any issues.
    Just don't want anything with too many loose electrons or something like that. Like foil and such, that sparkles.

    And the reply to the reply about microwaving it.. well let's just say none else thinks it a good idea to try.


    The point of the blowtorch is probably to fuse the outer layer to make sure there's no seams left.

    And, did he do most of it with a hammer? Because it just taps it and jumps to blowtorch with an almost complete ball.
    Last edited by snowblizz; 2019-01-11 at 04:19 AM.

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    PaladinGuy

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    Default Re: This video and the science/physics/chemistry behind it

    When one reads the manual some microwave ovens don't actually carry the "no metal" prohibition. A number of "silly science" TV programs etc. have covered various forms of metal in a microwave and I think the main issue that after you have had molten metal and a lot of sparks inside you no longer want to use it for food.

    In short, if you know what you are doing (and have the correct safety resources) you can use a microwave for things like this - but I don't so I wouldn't.

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    BlackDragon

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    Default Re: This video and the science/physics/chemistry behind it

    I have a microwave cookbook that says it's fine to put foil in the microwave--you use it to protect, e.g. the thinner part of a chicken leg so it doesn't overcook while the main bulk of the meat is raw. They say to just make sure the foil never touches the microwave walls and that it's nice and smooth, not crumpled.

    I think the main issue is that the microwaves induce currents in the metal, and if the metal gets close to an earthed piece of metal you'll get arcing between the two. Electrical arcs can cause serious damage to metal.

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    ElfPirate

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    Default Re: This video and the science/physics/chemistry behind it

    Quote Originally Posted by factotum View Post
    I have a microwave cookbook that says it's fine to put foil in the microwave--you use it to protect, e.g. the thinner part of a chicken leg so it doesn't overcook while the main bulk of the meat is raw. They say to just make sure the foil never touches the microwave walls and that it's nice and smooth, not crumpled.

    I think the main issue is that the microwaves induce currents in the metal, and if the metal gets close to an earthed piece of metal you'll get arcing between the two. Electrical arcs can cause serious damage to metal.
    Yes something with arcing.

    I've mircroed a butter package once with a foil type outer coating that started sparking. It's was crumbled a fair bit.

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    Troll in the Playground
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    Default Re: This video and the science/physics/chemistry behind it

    Quote Originally Posted by factotum View Post
    I have a microwave cookbook that says it's fine to put foil in the microwave--you use it to protect, e.g. the thinner part of a chicken leg so it doesn't overcook while the main bulk of the meat is raw. They say to just make sure the foil never touches the microwave walls and that it's nice and smooth, not crumpled.

    I think the main issue is that the microwaves induce currents in the metal, and if the metal gets close to an earthed piece of metal you'll get arcing between the two. Electrical arcs can cause serious damage to metal.
    The crumbling is an issue, since all sharp edges and point will inevitably have significantly higher concentration of charge, which leads to electron emission and sparks.

    At any rate, you can safeguard your microwave by putting for example a glass bowl over your plate so no spark can hit the interior of the microwave anyway. This is also a nice setup for creating ball lightnings (or something looking quite similar).
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    Ettin in the Playground
     
    Griffon

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    Default Re: This video and the science/physics/chemistry behind it

    I think this is basically a scam of some sort. I don't think you can compress aluminium foil enough that it will fuse with household equipment. It's interesting how he goes from a large ball to a small one in just one frame. The small ball is just too big to come from the compression of the large one, the large one is mostly air, by the time you got the air out, it would be much smaller. You've got about half a pound? of aluminium there in the small ball if it is solid, there just isn't that much aluminium in a typical roll of foil, and foil is a very expensive way to buy aluminium.
    Last edited by halfeye; 2019-01-11 at 01:28 PM.
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    Titan in the Playground
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    Default Re: This video and the science/physics/chemistry behind it

    And you can't melt aluminum without an inert atmosphere, or it'll oxidize.

    There's a reason why, in a five-minute video with, like, eight polishing steps, he jumps right past most of the compression.
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    Default Re: This video and the science/physics/chemistry behind it

    The video is probably bupkis.

    However, you can make a ball that shiny out of foil. You don't need many tools, and certainly you don't need anything dangerous like a torch. Just search for "Japanese foil ball" without the quotes, and you'll see a bunch of tutorials. It's a very simple process, but can take a long time and a fair bit of work..
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    Barbarian in the Playground
     
    Flumph

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    Default Re: This video and the science/physics/chemistry behind it

    Yeah, the video is bonkers.

    Chronos already mentioned how you'd want an inert atmosphere to melt the aluminum - otherwise you'd end up with a sphere with an aluminum oxide coating.

    Also, you can do this by compressing the ball with a hammer, and sanding it. Once it's smooth enough, apply metal polish, and you're good. It's just a long task, really.

    Of worthwhile note is that you can totally do this job with chemicals - you're using corrosion to smooth the surface instead of force. But this is pretty dangerous unless you have proper equipment and experience - and even then, hydrofluoric acid does not mess around.

    Edit: This actually looks like a pretty fun project. I should have some sandpaper laying around somewhere, and I can always run to the store for foil.
    Last edited by OutOfThyme; 2019-01-11 at 09:19 PM.

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    Barbarian in the Playground
     
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    Default Re: This video and the science/physics/chemistry behind it

    Quote Originally Posted by OutOfThyme View Post
    Chronos already mentioned how you'd want an inert atmosphere to melt the aluminum - otherwise you'd end up with a sphere with an aluminum oxide coating.
    It doesn't matter how you get there... if you leave the polished aluminium ball sitting in the air you're going to end up with a dull oxidized ball anyway.
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    Barbarian in the Playground
     
    Flumph

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    Default Re: This video and the science/physics/chemistry behind it

    Quote Originally Posted by aspi View Post
    It doesn't matter how you get there... if you leave the polished aluminium ball sitting in the air you're going to end up with a dull oxidized ball anyway.
    True, but heating up the surface of the sphere speeds up the rate of the oxidation reaction. It'll oxidize over time, yeah, but not as quickly as torching the aluminum in regular air.

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    Titan in the Playground
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    Default Re: This video and the science/physics/chemistry behind it

    Leave it sitting in the air, and you'll get a thin oxide coating that probably doesn't decrease the shininess much. Blowtorch it enough to melt, and you'll get the whole thing oxidizing, certainly enough that it wouldn't fuse together.

    And while HF doesn't fool around, I'm sure that there are less-nasty chemicals that could also be used for polishing. HF is mostly just used for glass etching.
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    Barbarian in the Playground
     
    Flumph

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    Default Re: This video and the science/physics/chemistry behind it

    Quote Originally Posted by Chronos View Post
    And while HF doesn't fool around, I'm sure that there are less-nasty chemicals that could also be used for polishing. HF is mostly just used for glass etching.
    A lot of metal etchants are mixtures of some kind. It's not uncommon to see mixtures of hydrofluoric, hydrochloric or sulfuric acid (along with other fun stuff like picric acid) mixed in something like ethanol or methanol.

    For aluminum, the ASTM standard that works decently for most aluminum alloys is using a hot sodium hydroxide solution and rinsing off with concentrated nitric acid. It's less terrible than HF, but still not something I'd recommend for someone without experience.

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