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Choosing an epoxy for a glowing knife

Levi HarrisLevi Harris ✭
in Student Projects
Hey everyone! First time posting here! I'm currently working on a low-budget film for a nonprofit featuring actors on the autism spectrum! Of all the exciting effects projects we're working on (not a few haha) I have a specific question. I'm trying to create a real life version of this drawing (I'll attach it below). The plan is for the blade to actually glow, and so we were thinking to cast epoxy tinted orange with a line of led lights inside and then painted over with metallic paint. I was wondering if anyone had any advice on which kind of epoxy to use so that it would be flexible (so as not to snap during light combat) but also not floppy. Any advice would be AMAZING and feel free to ask any other questions! 

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    Micah J.Micah J. ✭✭✭
    For an amber or orange colored blade that needs to be flexible and able to be lit from within, I would go with something like PMC-746 from Smooth-On.  It's a urethane rubber, about Shore A 60. You could design whatever is holding the LEDs to reinforce the rubber to keep it from being floppy while leaving the majority of the blade user friendly (think about a smaller version of the blade as the reinforcement). Incorporate this core, including the LEDs into the mold design. It's not necessary but, I would pressure cast it to remove any bubbles (make sure whatever mold you are using is also pressure cast or it will be ruined when casting the blade). Painting might be an issue but, you could add metallic powder pigments to the mix when casting. This will affect transparency so, I would be sparing in how much I added. You could also "paint" the interior of the mold with metallic powder pigments to bind them to the blades surface. Again, be conservative or you lose transparency. 
    It may work out for you to omit the metal paint and just go with the rubber. It's semi-transparent but, might look cool.

    Another idea would be to have the light come from the handle and cut a blade core from acrylic sheet plastic and overmold that acrylic sheet with clear rubber or silicone.  Look up images of "edge lit acrylic" for what I'm meaning. it may help to "frost" or sand the acrylic sheet so the light is universal up the blade. You could also add an extra layer of cool by inscribing sigils or something on the surface of the acrylic which will catch the light even more. No need for an LED strip up the blade, the acrylic will diffuse the light. 

    Cool design, by the way.
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    Levi HarrisLevi Harris ✭
    Micah Thanks so much! I'm absolutely going to be looking into the edge lit acrylic. If I do go that direction, should I still use the PMC-746 around it for the rest of the blade? You're response was invaluable thank you a MILLION!
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    Micah J.Micah J. ✭✭✭
    Or a clear silicone like Sorta Clear 37 or 40 from Smooth on. If you go with the 746 you could use it for the mold as well, just make sure you get a good release spray, Ease Release is what we use. 
    Hope it works out
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    Levi HarrisLevi Harris ✭
    Just picked up some Plexiglas today to experiment! I'll post some pics soon :)
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