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  1. #11
    patanderson's Avatar
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    Good Idea! Now I'm learning a lot. A homemade flashbulb seems interesting to learn. Thanks for posting this topic.

  2. #12
    ath
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    Quote Originally Posted by Eugen Mezei View Post
    Andreas, didn't know about the high impedance of the goldcaps. Just thought goldcaps have the highest capacity at the lowest physical volume. Speaking about goldcaps, I thought about using them for another application too. I wanted to use the spark to perforate thin alufoil to make pinholes. Do you think I am better of with normal electrolytics for this application too?
    You are right about goldcaps but in this case you want to draw significant current (after all that's why the energy is stored in the capacitor and not drawn directly from the battery). It may work with a goldcap though.

    Regarding the pinhole, are you sure that works? Goldcaps were developed for low current applications (e.g. buffering ultra low current electronics like static RAM for weeks or longer). Generating sparks is not low current. I would start with electrolytic caps or, if higher voltage is required, with foil capacitors.

    Shorting a 4700µF cap charged to 30V already gives some welding effect.
    Regards,
    Andreas

  3. #13
    Steve Smith's Avatar
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    Quote Originally Posted by ath View Post
    I would start with electrolytic caps or, if higher voltage is required, with foil capacitors.
    A normal, cheap electrolytic should work. Nothing fancy was used in bulb flashguns many years ago.


    Steve.
    "People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.

  4. #14
    ath
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    Steve, that last recommendation was for punching aluminum foil...
    Regards,
    Andreas

  5. #15

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    Quote Originally Posted by Steve Smith View Post
    Have you ever pushed a 9 volt battery into wire wool?




    Steve.
    While this is a bit OT, any outdoor photographers out there might be interested in my spin-off idea. First off, we know that steel wool burns with a nice warm glow.

    Now sometimes I want lighting (at night) that simulates the warm glow of a fire. (Usually I shoot in arid areas where there's precious little wood.) Next time I want faux-fire lighting I'll just light a wad of steel wool with a match or a 9V!

  6. #16

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    I think the old flash bulbs used magnesium....

    I would think the regular electrolytic capacitor would work just fine. It may have higher internal impedance and slower frequency response but at the speed we are talking about, especially considering its application, it's irrelevant.

    Metal fibers will burn explosively in pure oxygen environment. Please be careful.
    Develop, stop, fix.... wait.... where's my film?

  7. #17
    bobwysiwyg's Avatar
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    Quote Originally Posted by Eugen Mezei View Post
    Hope I'm in the right subforum. Have not found one about DIY.

    I intend to build my own chemical flashbulbs. It will be an oxygen filled and sealed glass recipient with aluminium foil snipplets.

    What I don't know is how to ignite the aluminium.
    I thought about running two electrodes with a tiny gap between them inside the recipient and connect them to a loaded condensator (best a high capacity goldcap) to produce a spark. Was this done so in the industry produced flashbulbs? Or was the ignition by incandescent filament?

    What I know is that in the industry produced flashbulbs a chemical ingitor (a priming paste or powder) existed inside the bulb that got hot and was sputtered around to ignite the aluminium or magnezium foil or wire.
    Can somebody point me to information what the chemical used as primer was, how it was applied and how it got ignited and provoqued to sputter?
    Why do you want to do this? I am not being judgmental in asking at all, just curious.
    WYSIWYG - At least that's my goal.

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  8. #18

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    What you are looking for is a pyrogen. You can find these compounds online via fireworks supply stores, as they are used to make electric matches for fireworks shows. Be careful, though. Purchasing the equipment and supplies to make e-matches is completely legal for anyone, but in order to buy premade e-matches, you need a BATFE Type 54 explosives license. Of course, the above only applies if you are in the USA, as I have no idea as to the laws in other countries.
    "Panic not my child, the Great Yellow Father has your hand"--Larry Dressler

  9. #19

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    Quote Originally Posted by tkamiya View Post

    Metal fibers will burn explosively in pure oxygen environment. Please be careful.
    And don't forget that commercial flashbulbs had a clear (or blue) lacquer coating to prevent the glass shattering from the heat when they were fired.....

  10. #20
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    The coating also was also often a colour temperature adjusting filter.
    my real name, imagine that.

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