The search feature and google hasn't really given me answers, so I'm going to ask: Would it be possible to make a replica darksaber?
To elaborate, the way it might work is to insert a black tube inside the hollow of a midgrade, non-ultraedge blade, maybe even replacing the film inside (probably not) to produce an opaque blade with a glowing outline. This, of course, would not work with string LEDs.
I don't know where to get the materials to try this myself, but I would like to know if anyone else thinks it's possible or might even try it.
Not really, no.
I mean, it's something I've seen asked more than once, generally with the question of a "black" blade. The problem is that, while it sounds cool, it doesn't really work in practical terms.
From your own description, you've got a black tube inside a blade. That black tube is going to nigh-impossible to fix in place, which has to be done so that the diffuser film doesn't get damaged when the saber gets hit. And it's not going to look right. You'd have a solid core interior, with light shining around it, rather than the rather vibrant core that lightsabers have. Not to mention that a giant black tube would absorb radiant energy like crazy, which would cause a degree of expansion within the blade.
And there's the fact that black is the result of all colors within the visible spectrum being absorbed - it wouldn't emit.
Basically, the quick answer is that no, it's not really possible at this point in time.
You COULD perhaps try an Adegan Silver saber and apply LEE filters to get "black" light, but again, black is kind of the antithesis of light...