2 How they work
--a What is your packing?
3 Why a CM still is annoying & a simple mod to help
4 Getting good neutral without a carbon filter
--a The ferment
--b Stripping run
--c Spirit run
5 Other spirits
So, the homebrew shop saw you coming and now you have a Still Spirits / Essencia / something similar 25l CM still that looks more or less like this one. Don't despair, because while the still you have definitely isn't the best, you can still use it to make spirits the will beat the turbo's and essences that your brew shop is selling hands down. This guide will help you to learn how, and is aimed only at users of these particular cm stills, and is not really applicable to anything else such as the taller CM columns that are advocated in some parts. It is written for a user that doesn't know any more than the brew shop has told them, which is the sad case for many people in my country (I was one of them!). I'm not trying to promote a flawed design here, but rather help out folks that got excited and made an uneducated purchase. I will try to link all the jargon to the wiki entries and so on to help the novice reader. Enjoy!
2 How they work
The biggest thing to get your head around with those cm stills is how they work. here is a quick and rough explanation in my own words:
Reflux stills work by sending a portion of the vapour back down the column as reflux. a CM still does this by cooling the column, so that most of the vapor condenses, and then a little bit 'makes it past'. This portion that makes it past is generally the lower boiling point compounds like ethanol, and the heavier, higher boiling point stuff (water) will fall back down (more experienced people reading this will realize this is an extreme simplification). In a taller column the falling condensate would mingle with the rising vapours and so on, but the columns are simply too short on these stills, and the condensation tends to happen on the sides due to the water jacket design (as opposed to a cooling coil in the column). This is why you'll never get as pure results as a taller column like a VM or LM.
So, hopefully you sorta get how the cm is working from that.
If you are confused about the different types of reflux still, BW Redneck has a good explanation of VM/LM/CM here.
2 a - What is your packing?
The column of these stills is normally packed with something to assist the reflux condenser in knocking down vapour. If this is copper scrubbers, fantastic, skip the rest of this section. If this is marbles, stainless steel packing, rings, or (the worst I've seen) a single marble, you should seriously consider changing to copper scrubbers. Your brew shop will probably sell these, they provide much more surface area, and this helps boost the ABV in our spirit run (see later). Depending on where you are, you may be able to get something in the supermarkets as well, but be careful that the material is safe for use in stills. Do your research on this.
3 Why a CM still is annoying & a simple mod to help
Now the reason that CM's are such a pain to run and are generally regarded here as more effort than they're worth is that you cannot control the 'reflux ratio' (the amount collected vs amount returned) by any means except cooling water. This sucks, its really hard to get right, so you should do yourself a favour and get a valve on your cooling line that you can operate by your still. garden / household taps simply do not have enough fine control in the lower flowrates especially on spirit runs (water takes more energy to knock down than ethanol. More detail on spirit runs later). Make sure you put the valve on the INPUT side of the cooling system, or all those push on fittings will burst off under the pressure at high temperature, potentially covering you in very hot water.
If you are on a water supply that has a tendency to vary in pressure, you may have problems with pressure swings changing the coolant flow for you. I use city water with rock steady pressure, so it isn't a problem for me, but if you do strike this, Hawke has the following advice:
Hawke wrote:A simple RV, (Caravan) pressure limiter would work. These go inline on a garden hose and limit pressure to no more than 40psi, without limiting flow. http://www.campingworld.com/shopping/it ... ator/26191" onclick="window.open(this.href);return false;" rel="nofollow
4 Getting good neutral without a carbon filter
Now for all their disadvantages, if you've got one of these already, you might as well work with it (well that's my thinking anyway, some will disagree). They can still be a good start to this hobby and you will learn a lot running it.
4a The ferment
The first step to creating a good neutral with these stills is to address your ferments. As we can only get 90% with these units, that's an extra 5% of flavours getting through when compared with the taller columns, so a clean ferment is vital. I strongly suggest shying away from the 48 hour turbo yeasts and so on, they produce some awful tastes. The only 'turbo' I've found to be any good is Essencia Super 6, which is nice and clean with some fruity notes, although I put in less sugar than recommended to avoid stressing the yeast. If you are really into your turbos for whatever reason, I'll not judge but this thread will help you get better results from them. If you aren't too attached to your turbos, Birdwatcher's Sugar Wash and Wineo's plain ol sugar wash are excellent, easy alternatives that will produce cleaner results than turbos. Yeast will produce fewer off flavours if you don't stress them out, so keep the temperature well within their tolerance and stable (colder end of the spectrum is good, I generally keep my washes at 21*C) and don't start with a really high specific gravity by putting in too much sugar, 1.08 is a good target for a clean, fast ferment.
Another easy way to make better spirits is to let your wash settle out nicely after its been done. I know, patience is hard, but seriously... just rack off the wash (leaving all the crap behind) into something else and LEAVE it for a day or two at least. There are commercial clearing / fining agents, I prefer to use time, personally. Then rack again into the boiler. Easy, you've got a clean wash
4b Stripping Run
As you read this site / forum, you'll notice a lot of talk of stripping runs. This is a rough and fast distillation through a pot still, to cut down the volume for the subsequent Spirit Run, in which you need to take care with cuts and so on. This may sound like double the effort, but a stripping run requires minimal attention, leaving you free to do other things in your shed and so on, and then only one in four distillations requires attention. It works out as a net time gain for me, but it also helps to make the product cleaner and stronger (it's been distilled twice, yeah?). I have achieved my best results (by far) for neutral when doing stripping then spirit runs.
There is a lot of info around on stripping vs spirit runs (parent site), but basically you strip the settled wash with a pot still, reduce the volume, take everything down to about 10% abv. Store this until you have enough, then dilute the 'low wines' (stripped wash, no wiki entry on it sorry) to 40%, and put it back in the boiler. Its easier to judge how much you have if you dilute to 40% right after distillation, but then you need more storage, so up to you. This is the spirit run, and you want to reflux it (for neutrals anyway). This run will take a bit longer, and need attention, but you'll probably do three strips (Which you can just turn on and do other things, though I'm not condoning leaving a still unattended, I do other things around the shed) to each careful spirit run.
These CM stills can be detuned and run like a pot still for stripping. This is a really, really useful 'feature' because the little cm columns are short enough to be effectively run as a pot, unlike true reflux columns which generate a lot of reflux due to height alone.
To detune, rip out your packing (the scrubbers, marbles, or whatever is in the column), and change the hoses around so that water is still going to the condenser (the offset bit where the distillate comes out), but not to the reflux jacket on the column. remember to always put cold water in at the bottom of the condenser. So, now you have a pot still, a clear path from pot to condenser allowing for minimal reflux. I'd take a photo of the hose set up but I've gotten rid of my CM now... maybe someone else can add one?
4c Spirit run
The spirit run will take longer than the others, so make sure you've got enough time. My spirit runs took about 5 hours from memory.
First thing you need to do is put the packing back in the way you found it, and set the hoses back the way they were (water enters at the bottom of the condenser, then goes from the condenser to the bottom of the reflux jacket, and then to waste). When you start the spirit run, jack the cooling up quite high. you want 100% reflux, i.e. the reflux jacket needs to take enough heat away from the vapour rising up the column that it will all fall back down the column. These columns are too short to equalise properly, but it is still beneficial to let an even boil get going in the boiler. Let it boil under 100% reflux for about 15 mins (temperature will be probably 50-65*C) , then slowly decrease the cooling, and you will start to separate out distinct fractions in the foreshots / heads. It isn't commonly accepted here but CM is actually very good for heads compression. Remember, take it SLOWLY, nothing good ever came fast. 1 drip per second is what I aim for. It will 'auto shutdown' several times, and you'll have to decrease the cooling again to get the next fraction. Don't rush it.
After a while of foreshots removal (maybe 30-45 mins) you'll be starting to get into the good stuff. As a general rule, the absolute minimum to throw away from three stripped 25l washes is 150mls of foreshots (don't recycle), and then I generally take the next 200-ish ml as heads (ok to recycle) as well and recycle them in my next run. The cut to body is best done by taste and smell, but that will be a problem if you are planning on turbos carbon filtering etc etc, and takes experience to recognize. when you're starting out, using nice, conservative cuts is the best substitute. you may loose a ml or two, but who cares, you're probably getting about 20ish liters off this run.
after you've taken off the foreshots to throw away, and heads to recycle, you should be into the body at about 77-78 degrees. you can then open it up a bit more (reduce cooling) to get a faster collection rate, I sit there and increase the collection rate until I'm happy with the balance of collection rate / output abv.
Remember, collection rate is inversely related to the amount you reflux as well as the abv %: 'the faster you go the bigger the mess'
I personally find that the temperature is easier to set on the 'down stroke', as in decreasing the cooling. I can never quite land it in the right spot when I go to far and have to increase the cooling, so if this happens I put it right back to 100% reflux and slowly start it again. This normally happens several times during a run... the explanation for this is that as you progress through the run, the proportion of ethanol in the vapour going up the column decreases, and it takes more cooling to knock it down. This is a intrinsic disadvantage of the design, and cannot be avoided.
At the end of the run, your temp will begin to 'want' to rise up past 79-80. Your collection will slow quite drastically as well, which will show you that this isn't just a need for more cooling like the the above scenario. This is when you need to switch containers for tails, and keep collecting as much as you can (will require cooling tweaking) until the temp goes past 84 and the collection rate slows even more. Throw the tails and heads back in to the next run to recover the booze.
If you use that method with a nice clean neutral wash like birdwatchers, you won't need to carbon filter, given careful cuts and good control over the temperature for the course of the run. You should be able to achieve 92% on your spirit run if you are careful.
5 Other spirits
As discussed above, these stills detune easily into something approximating a pot still. They ain't perfect, but will do the job.
For flavoured spirits like rum / whiskeys etc, just do two runs through the detuned still, and make careful cuts on the second run. To play this game really well though you'll need an power controller for your element, or a smaller element (high power in a pot still tends to 'smear' the cuts). I'm not really going to go into detail on this, pot stilling is a entirely different game, but knowing that you can use this still for pot stilling recipes should be all you need, pot stilling techniques are discussed in this section of the forum
I hope that this helps someone that did what I did, go to the brew shop to learn about stills rather than home distiller...