Double Distilling

[redeye_green]

Hello,
I am having trouble getting my head around double distilling. I have an EasyStill and I've done about 3 runs so far. They all seems to have a smell and although are drinkable I would like to get the result cleaner. I am thinking of double distilling but I am unsure how. Say I run 4L on the first run and collect 700ml, firstly; should I throw out what is left in the still? Secondly, do I just put the 700ml back into the still and start again? Is 700ml enough to run it on?

Sorry for the silly questions!

[Capt-Cudellez]

Hi Redeye - Keep the 700ml, chuck whats left in the still. Then continue to run the rest of the wash.and keep the output each time.

So do 5 x 4L runs of wash, and collect the 700ml each time. Take the 3.5L you have collected, add a some water for safety, and run that back through the still.


CC

[mozr]

I have been keeping 1500ml of each 4 litre stripping run coming out at 40% ABV.

Isn't 700ml being a bit stingy?

[Capt-Cudellez]

BTW - I have never ran an air still so I am unfamiliar with ABV and volume you pull off - just used the numbers redeye gave - didn't mean to imply in my post to only pull 700ml.

[Jimmy]

With an airstill, what you get out all depends on what you put in, i.e. the strength of the starting wash.

If you start with a wash at 16% then you'll get about 1520ml at 41% overall BUT the purity of the alcohol coming out of the spout at the end will be 13% which is way into the tails part of the run.

Many people suggest only collecting output above 50%, which in this case would mean stopping at 677ml (these figures all need to lose 50ml off the top for the heads by the way).

That might seem stingy, but if you're going for purity then it's important because by the time you get to 870ml total your output is down to 43%, and by 1049ml it's at 35%.

As ever, my recommendation is to use the calculator:

http://homedistiller.org/pot_calc.htm

Numbers are 4 / 16 / 20 / 320 / 320 / 25 / 20

Key to using the calculator is knowing what you're putting in, so that's why I recommend a stripping run which you can then use to measure the input strength with an alcometer instead of relying on calculations from the SG. Then you can be pretty accurate about what is coming out at any given point in the run. There are downsides to the airstill but this is one of the good points!

So, my recommendation - work out how much wash you have (from 25 litres I usually bank on 24 after racking). Divide by 4 to get a number of stripping batches (so 6 here). Decide on a decent amount to take based on simplicity and a nice round number if possible - in my case, when I started I had three glass demijohns for temporary storage so I decided that after my stripping run I'd like to be left with 3 batches of 4 litres. I would therefore take 1.5 liters on each stripping run so 1.5 x 6 = 9 litres, three in each demijohn and a litre of clean water to make up the batches. Then measure the strength, use the calculator, and you're away!

Again what I always say - this is what I do, and it's just a starting point, doesn't mean what anyone else does is wrong. I do love the calculator though, it's like a virtual parrot if you use it right!

Oh, and one final thing - don't run it on low amounts, if you have less than 4l then just dilute with clean water. It seems counter productive but it'll actually work better.

[redeye_green]

Thanks for all the replies, it certainly clears things up.

@Jimmy: when you say you collect 1.5L off each stripping run (and sorry for being dumb here) do you mean that you actually take more than then 700-800ml talked about? So, roughly half of the first run includes some lower alcohols?

I have a 25L wash on at the moment. In a few days I will rack it off into a FV and have about 24L. As you say, I will run 6 x 4L runs taking 1.5L of each - then combine the 1.5L (and top up) and then this then becomes my second run (possible 3 second runs). How much of the second run should I keep/discard? Or does this depend on me (flavours etc)

[Jimmy]

No worries, it's all about the learning!

A stripping run is basically a quick and dirty way to get the initial wash up to a decent strength. Imagine you wanted to get the highest quality spirit - you could divide your 24l into 4l batches and take ages over each one, taking off the foreshots, making cuts, etc. Or to speed the process, just do your rough stripping run and take something arbitrary like 1.5l. The exact amount isn't important, you can work it out roughly by using the calculator and seeing what strength the output is (purity) for each volume of distillate. You don't even have to take off foreshots, just literally bang it through as quick as you can.

Straight away you've gone from 6 batches to 3, which means you're then free to take more time over those and get a higher quality product, not to mention the benefits of it going through twice.

So the 1.5 litres is just a rough amount but it'll work fine for a normal type wash and the maths is easy. On the second lot of runs, how much to take depends on the strength of what you're putting in, but the beauty is that because you're now dealing with spirit you can use an alcometer to measure it unlike wash which you can't. It'll be more than 700ml on the second run, because proportionally there is more alcohol in the still - play about with putting different strengths into the calculator and you'll see what I mean!