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Thread: Obsidian at home?

  1. #1 Obsidian at home? 
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    So with minimal research, I have found that by rapidly cooling felsic molten material, obsidian is formed... any specifics I should know before I continue?
    Nextly, granite is a common felsic material, so if I were to melt it in an industrial kiln, or more likely, with thermite, and then gently pour cool water over it (say it was in a mold), then would obsidian glass over? Could I mold obsidian shapes?
    There has to be something wrong with this process, there always is. What is it?


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  3. #2  
    Reptile Dysfunction drowsy turtle's Avatar
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    What do you need obsidian for? Trying to melt granite in your own home sounds like a fairly daft idea to me...


    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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  4. #3  
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    Well, for one, you can make the coolest, sharpest homemade sword of black glass ever.
    Melting granite in the basement seems bold to me too, but it's only hypothetical... To an extent.
    On a related note, you can make tungsten carbide in your basement too.
    So how fast must it be cooled? Air cooled, or should you pour cool water over it? Would it be tempered or shatter if you put it in the fridge?
    And the original question, would it or would it not work?
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  5. #4  
    Reptile Dysfunction drowsy turtle's Avatar
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    Granite has a specific heat capacity of approximately 0.8kJ/kg/K and a melting point of perhaps 1000-1200K. (N.B you will need to use granite with a very high silica content)

    Melting a kilogram of granite (which is far less than you would need to make a "cool black sword") would therefore take around 800kJ.

    Assuming all the heat is transferred to the granite (which it wouldn't be), this is around a mole of Iron III Oxide and 2 moles of aluminium. This is around 214g of premade thermite.

    In reality, you will need to do all this inside a good insulator (unless you're ****ing mad) and most of the heat will still be lost to the surroundings. So let's say 500g+ of thermite.

    Then you have the problem of seperating the molten iron and aluminium oxide (left over from the thermite) from the molten granite - have fun with this.

    Assuming you somehow manage this, it essentially becomes glass-making, except with incredibly impure silica. I don't know how it's done in glass-making, but I suspect dunking it in cold water to solidify it will cause it to shatter.




    I would highly reccommend not trying this at home. By far the most likely outcome is setting something on fire, quite possibly yourself.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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  6. #5  
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    Alright, you put sand and granite in an arc furnace?
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  7. #6  
    Universal Mind John Galt's Avatar
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    Why not rent a volcano?
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  8. #7  
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    I will rather suggest you to use some rhyolite lava.
    There are granites and granites, so many varieties that you might end up getting something else.
    But frankly, to get the coolest, sharpest homemade sword of black glass ever, I think it is a lost of time, energy and granite/rhyolite.
    I suggest rather to spot a volcano which can produce obsidian, get some nuclear devices from one "Stan" country and trigger a volcanic eruption.
    "LÓ, tout n'est qu'ordre et beautÚ,
    Luxe, calme et voluptÚ."
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  9. #8  
    Reptile Dysfunction drowsy turtle's Avatar
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    If you're not actually going to be killing people with it, why not simply make it out of black glass?
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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  10. #9  
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    Duly noted... But you can do other things with homemade obsidian, and I don't live near a rhyolitic volcano, so...

    Herm. I'm sure you can get the sand/granite mixture close enough with some tinkering. Thanks.
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  11. #10  
    Iuvenis ducis Darkhorse's Avatar
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    LOL Homemade Obsidian. People don't make homemade obsidian for the reasons above. Just because nature does it easily doesn't mean you can duplicate it in your kitchen.

    You may want to tour a glass blowing factory to understand better what you are proposing. Molten glass is extremely dangerous and no one should be messing with it in their backyard without some proper training. Not only is it hot enough to immediately give you a 3rd or 4th degree burn (see wikipedia for a definition) it is also extremely caustic. Professionally made kilns have a lifespan measured in months.

    Tempering glass is not as easy as sticking it in your fridge or quenched it in water. Pouring water over it most likely will cause it to explode and send you to the hospital with glass shrapnel wounds, if not kill you. Seriously get some training then revisit this idea.
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  12. #11  
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    do you happen to live near a steel factory or a foundry ? i'm sure they could show you examples of obsidian-like slag
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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  13. #12  
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    Wow Obsidian at home . .? . .Why . . .? . .Remelt Obsidian at home . .? . .Why .. .? . .I suppose you could . . .Does any one know someone could remelt Obsidian . . .Why . . .Why do you ask why . . .Dont you know . . .If you realy need to ask why you probably wouldent get it . . .Or more acurately Probably wouldent want to understand
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  14. #13  
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    An obsidian sword would be useless, since one blow would shatter it. So I assume your sword will be for display only. If you want a sword that actually works, there are plenty of places to buy one made of quality iron.

    So if you want a black glass sword for display, take Drowsy Turtle's advice, and go to glass maker, and get him to make you a black glass sword.

    Here in New Zealand, obsidian is of importance in the historical sense. We have a volcanic island (called Tuhua in the Maori language. Tuhua is also their word for obsidian.) which has tens of thousands of tonnes of the stuff. In pre-European days, when our native people, the Maori, lived a stone age existence, obsidian was a vital tool, since it was the only material they had access to that could cut properly. It was traded up and down the coast by the hundreds of tonnes, carried in manually paddled dug out canoes. They did not make glass swords!
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  15. #14  
    Reptile Dysfunction drowsy turtle's Avatar
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    To be fair, skeptic, the tools they had were being knapped, not forged. Knapping a sword out of a lump of obsidian would be problematic, and yield a tool only useful for a type of war that didn't exist in pre-European New Zealand.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
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  16. #15  
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    Turtle

    The Maori had lots of wars, and were very ingenious in shaping the materials they had available for killings. If they could have knapped an obsidian sword, they would have. But of course, the stuff is too brittle.

    On the other hand, flakes of obsidian had such a sharp edge that they were valued. Archaeologists have found lumps of obsidian from that volcanic island in middens (ancient rubbish heaps) all over New Zealand. The only other material so widely traded was NZ greenstone - a variety of jade - which was prized for making a range of tools and weapons.
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