Well I don't know if I was "driving" it wrongly, or whether it's not worth the effort to try this mod.......
The temperature sat nicely between 78 and 80 degree's C, but it was just chucking out clear distillate at about 70 or so % ABV
Now I know that I can normally get between 80 and 85% ABV with just the condenser head directly on top of the boiler.
So for the moment, it looks like I'll scrap the idea of making an extention like that (damn things too tall anyway.....).
I'm now thinking of looking into seeing if I can try to make a "mini-bokabob" (details over at homedistiller) column and then connect it in the same way to the top of the SS boiler. Though before I go for it, I need to see about getting a heat source to silver solder - plus I know that I can find 54mm copper pipe, but if it needs anything larger, then I might have problems. Plus there's the issue of the connectors to scale the bore of the pipe down to 15mm (that being the size of the hole in the SS boiler lid....).
So not all is lost, it's just part of the learning process...... as I'm convinced that there must be a way where I can make something that will reflux and produce 90+ % ABV in "one pass"..... rather than having to run multiple distillations to achieve that level of purity.....
Hey ho!
p.s. Oh and I knew that something wasn't quite right as it seemed to produce the distillate at about 1.5 litres per hour, so it's quick, just not as efficient as I'd hoped.....
