Heh heh heh... Now we're adding sight glasses? At the hobby level? Too cool!
It just dawned on me that Manu, and for sure others, thinks of these stills as reflux still, but they aren't. There is some natural reflux when you get the power right, but it's not a "toss it all back and re-distill everything" type of reflux, which is akin to holding down the trigger on a machine gun and firing until nothing could survive. Instead, these are true fractioning heads, where a bit of natural reflux does take place, but the power is what determines what goes where, and we can efficiently separate what we want from what we don't want. As long as OldDog doesn't crank the power up high enough to "push" a lower volatile up to his collection plate, it won't be there, and will simply stay within the column, collecting in the lower plates and being re-distilled there, and anything more volatile than he wants shoots past the collection plate(like a cheap bastard sneaking out at church

). The whole trick is to find the power necessary to keep the tails under the collection plate, and the heads above it. Quite efficient if you get it right. With mine, I have to keep the power down low enough to get all the higher volatiles(fores and heads) out of the system(which is why I collect them), and when they're all gone, I can increase the power to get the hearts, but not too high to now "push" the lower volatiles past the uppermost plate.
We don't control these with reflux; we control these by choosing how high up the column(s) we wish to push the various volatile compounds at which time.
As I said before, when forced to think through -why- these things work, I learn more about them myself. Thanks for making me think further; we'll get our finger on the pulse, yet. I can now see that where mine needs some tweaking of the power at various stages for it to work the way I want it to, OldDog's Coffey style head can do it without operator input, once the operator finds exactly the power required to hold the tails below the collection plate, and yet force the heads past it. Exactly what a continuous still would need! Yet in a batch still, it can still work; only we'll have -some- early heads as well as late tails.
Neat!