- Pot Stills in depth
- Pot Stills designs
- Effect of the lyne arm
- Urban folk Still
- 280 liter Pot still
- Reflux Still designs
- Thumpers, Doublers and Slobber boxes
- Double walled Boilers
- Gin heads
- Vacuum Stills
Pot Stills in depth
Both Pot & Reflux stills are relatively simple and both produce liquor. The difference is just that for a reflux still you have a packed column before the condenser, and you get some of the vapor to condense and drip back through the packing. You do this if you want to make clean/pure/tasteless alcohol of around 75%-96% purity for adding flavors to, or making gin/vodkas etc.
If, however you just want to make straight forward whiskey / schnapps etc. with some flavor, you can use either a pot or a reflux still.
An interesting note is that some copper in the alcohol vapor path is beneficial. For Rum it is essential to only use acid proof stainless steel type 2333 / 316L or Copper.
Normal low grade stainless or Aluminum will produce unpleasant tastes and color. Some people who have built all-stainless steel stills have found there to still be some smell +/or odor in their neutral spirits, which goes away when they put some copper in (usually replacing the scrubber packing with copper scrubbers).
The heads are obtained in the early part of the distillation. These are the substances that volatilize the easiest and fastest. They are aggressive, contain many watery substances and are low in alcohol. They are added to new wine for re-distillation.
The middle cut of the first distillation is the brouillis. This is retained for careful filtering and a second distillation. It takes about 8 hours before the brouillis has been fully obtained. The last portion of the distillate, the tails, is weak in alcohol and is combined with the heads for inclusion in another first distillation.
The brouillis has an alcohol content from 27 to 30 percent. It is redistilled and again separated into fractions. The early distillates form the heads and are recycled as before. The portion that will become Cognac is drawn off at 70%; this takes about 5 hours. As the distillation continues, the alcoholic strength begins to very slowly decrease. When it drops below 60% the heart has been fully collected and the distiller now draws off what is known as seconds.
The last fraction is again termed the tails. The seconds are redistilled either with new wine (in a first distillation) or with the brouillis (in the second distillation). It is considered a quality factor as to how much is used with the wine and how much with the brouillis.
Rémy Martin, for example, only uses from 20 to 25 percent of the seconds with the brouillis; the remainder being mixed with new wine for a complete (two times) distillation cycle. Use of excessive amounts of seconds in the second distillation is considered to be detrimental to the quality of the finished Cognac.
Separation into the various fractions and, especially, the heart of the second distillation is considered of critical importance and is part of the art of distillation (as opposed to the science). Skill and experience count for everything here.
- If a still batch contains 2 500 l wine and lees (total of 90%) and heads/tails (10%). Some firms distill the wine on its lees. Rémy Martin does this and considers it to be one of their important quality factors. The size of the alembic is also important; 2 500 l is considered relatively small.
Yield from Rémy Martin 1st distillation:
• Heads = 12 liters @ 60%.
• Brouillis = 8 hl @ 28%.
• Tails = 100 liters @ 3%.
• The second distillation again starts with 2 500 l. containing secondes (20%) and brouillis (80%)
Yield from 2nd distillation:
• Heads = 30 liters @ 72%.
• Cognac = 700 liters @ 70%
• Secondes = 600 liters @ 30%.
• Tails = 150 liters @ 3%.
Fresh distillates, called Eaux-de-vie at this point, not Cognac, are taken to the Cellar Master of whichever firm(s) the distiller is working with. There, a judgment is made as to the suitability for that particular firm considering their style, quality standards and so forth. Such selections are made prior to March 31 of each year (Cognac is distilled only until March 31) and the spirits are given a rating of 00. On April 1, the rating changes to 0 and the spirits will be moved to wood for their long and slow maturation. On the first of April the next year, it is 1; the following year, 2 and so forth. This continues for a maximum of 8 years. The aging continues, of course, but the official age ends at 8 years
Pot Still Designs
There are just so many ways, and it really depends on what you are available to you. One factor to consider is the angle of the lyne arm. Even with a pot still you get a little bit of vapor condensing on the head & arm, and running back down into the pot as a bit of reflux. Depending on how much internal reflux is going on, the flavor will vary. An upward sloping arm will cause much to run back into the pot, thus cleaning & lightening the vapor more, whereas a downward sloping arm will send the entire vapor towards the jar, and you’ll collect a heavier flavor. Some also have a bulge in the head. This construction then expansion causes some of the vapor to drop out, and again increases the reflux, and lightens the spirit.
Diagram of a very cheap and easy to make home Pot still
For a pot still, the lyne arm (as it comes off the still body) should go up at a 45 degree angle for 60 cm, and then it should drop into the condenser. The diameter of the tubing depends on the heat – for most stovetop models (typically built out of a pressure cooker) 6 – 13 mm tubing is used for the lyne arm and the condenser. The narrower the tubing is, the lower the heat setting you need to use.
Effects of the angles of the lyne arm; it can go high – straight or angled down.
The condenser running off of your pot still can be whatever diameter you have (provided it’s no smaller than 6 mm. Also, remember that you don’t have to have a coiled-tube condenser- you can use a jacketed model just as easily. With stovetop pot stills there is a lot of room to adjust the materials dimensions, because the heat source is so easily adjusted.
The shape and height has an effect on Rum/Brandy/Whisky -flavor
- Traditional Alambic. This is descended from stills used by alchemists. It consists of a domed cylindrical boiler with a bulbous still head. It sits in a brick furnace. From the still header chamber, the lyne arm usually slopes downwards or is U-shaped (‘Swan’s Neck’). The condenser is a coil in a tank of water. Raki stills, moonshine stills and the ‘Alambic Charentais’ for making cognac are examples.
- Varied Boiler shapes.
- Conical, classic whisky pot still (‘Springbank’ whisky)
- Onion shape, slightly fatter than the classic shape (‘Glenlivet’ whisky)
- Pear shape (‘Vintage Islay’ whisky)
- Varied Neck (Column) shapes and heights.
- Conical column from boiler. The smallest whisky stills are at ‘Edradour’ and the tallest at ‘Jura’, ‘Bruichladdin’, ‘Glenfardas’. The stills at ‘Glenmorangie’ whisky distillery are ex gin stills and are the tallest at 5.3m
- Boil ball and conical column (‘Strathmill’ whisky)
- Boil ball and cylindrical neck (‘Lomond Still’)
- Additional reflux feature in column. Column length and the Milton Ball header chamber create reflux, but some necks are cooled with running water to increase reflux (‘Fettercairn’ whisky). The traditional Australian brandy pot still has a ‘Brandy Ball’ water jacket at the top of the column. All are open columns. The ‘Lomond Still’ has 3 adjustable plates and is used as a wash still at ‘Scapa’ whisky distillery.
- Carterhead Still. The column contains a basket holding the gin botanicals (‘Bombay Sapphire’ gin’)
Varied Lyne Arms.
- 30 degree downward slope
- 30 degree upward slope (‘Deanston’ whisky)
- U-shaped or ‘Swan’s Neck’. Alambic Charentais’ for cognac, ‘Plymouth’ gin’, ‘Talisker’ whisky, ‘Lagavulin’ whisky.
Knowing that stills of a certain size and shape yield spirit with a particular flavor profile is all very well, but applying this knowledge the other way around is far more challenging. In fact, designing stills in order to produce a spirit with specific characteristics is merely a starting point, as this is only one factor in a complex (and not always fully understood) equation, which also includes the spirit cut, heating method, rate of distillation and type of condenser.
Even the relationship between the wash and spirit stills is difficult to quantify beyond stating that the new make spirit is shaped by wash stills and refined by spirit stills. But if the low wines aren’t right, the spirit still can’t correct them (and if fermentation is mismanaged, distillation can’t fix that either).
A boil bowl (bulbous section between the boil pot and neck) can vary from being mildly to acutely convex (the more convex, the more reflux). When vapors carrying heavier flavor compounds expand into this larger, relatively cooler area, they condense and return to the boil pot.
Dalmore Whiskey Distillery effectively doubles up by having a cooling jacket (also known as a water jacket) between the boil bowl and neck of the spirit still through which cold water circulates (using the same water source as for the condenser). This practice dates from 1839, with the oldest jacket still in active service dating from 1874.
Fettercairn Whiskey distillery has a different approach and yields a similar result. From a circular pipe located at the top of the spirit still, cold water runs along the neck and collects in a trough fitted around the still (from which it also drains). This has the effect of “giving the vapors inside a little fright” according to Distillery Manager Willie Tait. His more technical explanation is that cooling a fairly short neck gives it the effect of being much taller.
While purifiers are rarely seen, this is a feature of Glen Grant’s wash and spirit stills. As vapors leave the still and enter a copper pipe in a tank cooled by water, lighter elements within the vapor continue onto the condenser while heavier elements return to the still via another pipe. Without this procedure Glen Grant’s new spirit would be oilier and heavier, says Chivas Brothers’ Brand Ambassador. Similarly, in the opinion of Site Manager John Reid, a purifier in the spirit still increases the buttery; creamy notes of new made spirit.
But just as important as design features that make a still unique, is the manner in which the still is employed. Pungent, fruity esters are more evident in spirit collected between 68 and 72% abv. while a spirit cut extending to around 58% abv includes heavier, oilier, fatty acids. Consequently, altering or separating the spirit cut into batches collected at different strengths would enable varying styles of whisky to be produced from the same still.
How heating is utilized also affects the degree of reflux. Heating the still more rapidly increases the rate of distillation, driving off vapors more readily.
As this reduces the degree of reflux, it promotes a higher proportion of heavier flavor compounds. Driving vapors more rapidly also entails the risk of carrying over some un-distilled liquid, showing as a sour note in a new make spirit.
Correspondingly, a lower temperature means a slower rate of distillation, more reflux and a lighter (some say finer) spirit. At the leisurely end of the scale this means collecting around nine liters of spirit per minute, compared to around 20 liters per minute in the fast lane. Additional reflux can also be prompted en route to the condenser, using a lye pipe (or lyne arm) extending at an incline, which drives heavier flavor compounds back into the still.
By providing a greater surface area than a typical worm, a modern ‘shell and tube’ condenser increases the degree of contact between the spirit and copper, helping to strip out meaty, sulphurous compounds. However, worms (a coiled copper pipe of decreasing diameter set in a worm tub with cold water) do not necessarily result in a higher level of sulphurous, meaty flavors and the challenge lies in controlling the level of these characteristics to achieve a complex whisky.
Knowing these principles, is it possible to quantify the importance of the stills within the production cycle? We can estimate roughly usual 60% of the malt’s eventual flavor being attributed to maturation.
The Macallan Master Distiller expert says . “Less than 10% is accounted for by the barrel’s previous incumbent, and then maybe 5% is influenced by the barley variety and 5% by the strain of yeast,”. The crucial bit. “10% could be the wash still and 10% the spirit still, with the influence of the spirit still being divided into 5% each for the size and shape of the still and 5% for the spirit cut.”
Inspired by folk stills made from 200 liter steel drums, here is an urban version using:
- Pot: 20 L open top paint container (These can be ordered in new from some proprietary paint chain outlets/paint trade outlets, or get some free from painting contractors and clean them with paint stripper/turpentine. Container manufacturers sell them quite cheaply but normally only in lots of 50. Cleaning free empties is not too difficult and helps to recycle them.
- Outlet arm – 1.5m of 10mm soft copper tube, bent to form a “lyne arm”,up 200 vertically & then 600 long inclined upwards (to get some reflux) and then down 700 vertically. The 10mm soft copper tube is easily bent without flattening – use salt inside the tube to help prevent this, standard grommet for plastic beer fermenters, or improvise using cut sections of synthetic wine corks glued to both sides (they close in well).
- A 500 long Leibig condenser over the 700 copper tube section out of plastic T sections (2 x 19mm/13mm barbed PVC Tees) & 500 length of 19mm,plastic tube, clamps, silicone or epoxy resin, plastic glue.
Rubber grommets (as for plastic fermenters)
Plastic tubing – standard 13mm (3/4in) plastic tubing with plastic tap to hose connector, 10mm tubing for distillate (this fits on the 10mm copper tube, and for the water outlet from bucket to sink.
- Gas flame diffuser mat or water bath to get even heating.
- Thermometer -digital or mercury to measure pot vapor temp. Stop distilling at 91C
- Thumper – (Doubler) – 10 L paint container, with rubber grommets for copper tubing.
Worm condenser variant – 20L plastic bucket or cut down container, coiled copper tubing, grommets.
No welding – just glue, silicone, clamps. All this is suitable for most kitchen stoves and sinks. Obviously this is an introductory still for the beginner. Paint tins are not heavily coated. Kept dry it should last years – rust remover will extend this.
Safety aspects are so important, we don’t want any kitchens going up in flames! Switch the exhaust fan on to take away any stray fumes, even though the ring clamp is air-tight. I made the lyne arm quite long for partial reflux and to take it away from the stove. The distillate outlet tube goes down to the floor, well away from the stove. An electric stove might be safer, although apparently slower.
Describing of 280 Liter pot-still, doubler with shotgun condenser
People who do volume like them so much. Medium sized 280 l pot still with a doubler/ thumper 20 l and a shotgun condense. Sometimes in combination with a smaller still for running smaller batches and especially for running backings or low wines to “up” the proof quickly.
Copper sheets are soldered with silver solder and are used to build most components. Shotgun condenser made from an old, antique copper fire extinguisher.
Cut both the ends off and sand everything inside and out. Clean it to the “eat off of it” stage. Cold water enters the shotgun condenser from the bottom and exits the top to force the hot water out and this always keeps the bottom part of the condenser way-cool.
A shotgun condenser is basically a condenser with a water jacket to cool the steam and it has dozens of 6 mm copper lines that the steam goes through. Where the steam goes through looks like the end of a huge shower head. Bore two holes in the jacket about 7.5 cm from each end and solder a brass hose copper garden hose connector in it, top and bottom.
On the one you use for the bottom, you will put a spigot used to regulate the amount of cool water coming into the condenser. On the top one you’ll attach a garden hose and lay it out where the hot water can drain off the top of the condenser.
Two copper sheet circles are cut and clamped together and numerous holes drilled through them. The circles are placed inside the copper jacket and spot soldered.(silver) in place with a few pieces of the 6 mm line in to keep things lined up good. The lines are cut about 10 cm shorter than the jacket. Start putting the lines in and soldering them in place and soldering the circles in good, top and bottom.
On the first run, you’ll be able to tell if you have any leaks or not. You have to fix them if it does.
Make a tight fitting cap for the top to be sealed/ pasted on with cornmeal and water. The bottom does not require a tight fit at all. It is just there to collect the alcohol as it comes through and then out to the jug/bucket. With a shotgun condenser, you can fire the still as hard as you want to and you’ll have no problem.
Reflux still designs
This 150 liter working volume still is a typical still used by many of the artisan distillers
For neutral spirits you want a reflux condenser, so that the falling pre-condensate washes the rising vapor, reducing the water and impurity content, giving a cleaner, safer and higher purity product
Valved Reflux Still
The more contact you can achieve between the liquid & vapor, the cleaner and purer the product will be. To do this, increase the reflux ratio (the ratio of liquid falling to vapor rising) and the surface area that it is occurring over. A reflux can be made by packing the upper section of the column with inert packers (e.g. marbles (OK), rachig rings (better), or best – stainless steel pot cleaners (the ones that look like little springs. NOT the fine weave ones, or God forbid, those already soaped ready for use)), and cooling them by wrapping the cooling water hose around the outside, or passing a couple of cooling lines through the top of the column. Even better is to have either a separate condenser above them, or best – totally condense the entire vapor above the packing, divert some to keep, and return the rest to the top of the packing.
Using this still involves working with heat, steam, electricity, gas, and possibly explosive vapors. You must take extreme care to prevent injury, fire, or explosion if you ever decide to use the device.
Some view using a still to distill alcohol as being akin to boiling gasoline on your home gas or electric stove. Over time more than one person has been maimed or killed in the explosions and fires resulting from these activities. You must be careful at every step in these procedures.
Artisan Reflux Still
Plans of Thumpers, Doublers & Slobber boxes
Some distiller’s stills have a “thumper” or “doubler” between still pot and the condenser. This can even be a jar of sorts, half-filled with liquid (water, mash or tails).
This acts as a simple second distillation stage. Once it’s fully saturated with alcohol (hence better to start with something already containing alcohol), and up to temperature, the vapor leaving it will be doing the equivalent of a second distillation, using the incoming vapor as the heat source. Leading to that the vapor leaving a 15% wash will be coming off at 65%, after going through a second stage (the thumper) it will be at 85%).
Below is an excellent example of a thumper in action.
Starting with a small still and this was the answer. In a matter of four hours a still made, using 10 mm copper tubing. Condenser was made and encased in a PVC jacket with water circulating through it. Using grommets to pass the copper coil ends through, and some brass nipples for a water entry and return, this is hooked up to a small tabletop fountain pump in a bucket of water that circulates the water through the jacket. It really works well. Here we use a stainless steel cooker.
Cleaning it very well first, starting on the stove with boiling water prior to modifying it. While the pressure cooker is still warm – wash it with soap and water and this takes care of the grease they lubricate the lock with. In addition adding a “Thumper” or “Slobber Box”, using a pickle jar and a couple rubber grommets (works great), and a hotplate.
How does this work? The function is that when the main pot heats up, and begin giving off ethanol vapors (say at 40% purity at 96 ° C from a 5% wash)… these get passed into the thumper and try to bubble up through the liquid there. But because the liquid is cold too, the vapor will all condense if given the chance (e.g. small bubbles & water deep enough). A bit later on, the thumper liquid is starting to heat up and increase in ethanol content. Soon the thumper is at say 84 ° C, and the ethanol content is around 40% – that sounds like a second pot still doesn’t it? So the ethanol starts coming out of solution, though this time it will be at around 75-80% – hence the second distillation occurring – all for free, no additional cost or heating involved. Of course all this depends on how effective the thumper is at knocking down the incoming vapor – e.g. bubble size, depth of immersion, % alcohol in the vapor & thumper liquid etc., but you get the basic idea.
Look at the energy involved.
Heat of Vaporization/Condensation
Water = 2260 J/g
Ethanol = 855 J/g
So an incoming stream of 40% ethanol will give up about 1698 J/g, whereas to vaporize a 75% rich vapor needs about 1206 J/g. Then given that the flow rate of the 75% product is going to be only just over half of that entering, you have lots of energy left over, to first heat the liquid there during the initial phase, then to superheat the vapor once the thumper is up to temperature. So the low level alcohol vapor can more than happily look after itself in terms of redistilling itself.
Play with the spreadsheet, and test the various scenarios.
- Thumper vol. 1000mL and 0%
- Thumper vol. 1000mL and 30%
- Thumper vol. 3000mL and 30%
With a small thumper volume, the contents are fairly quickly heated up towards the liquid boiling point, but its % alcohol is quite low. For this situation, the vapor then tends to bubble up through the thumper, with no further enriching. What goes on is what comes out – no real increase in purity. The extreme case is one where the thumper acts to strip alcohol from the vapor, and produce a lesser strength vapor.
This situation changes a little if the small thumper is initially charged with a liquid of high % alcohol – e.g. the tails from the last run, say at 30-40%. In this case, the excess energy available is sufficient to cause the thumper to act like a second distillation stage – once it’s up to the boiling point of the % alcohol in there, the energy goes into vaporizing the vapor there, producing an output quite a bit higher in % than the vapor entering from the pot still. Unfortunately, because of its small volume, this isn’t sustained for too long, all the alcohol is driven off, and past a particular point in time, the thumper then simply lets the vapor bubble through & do nothing further, if not actually stripping the vapor & producing less than that off the pot still.
The best scenario for the thumper is where it is of quite a large size, and charged initially with a reasonable % alcohol. Even starting it with the same % wash as that in the pot still is an advantage. In this case, the excess energy from condensing the pot still vapor goes into releasing a vapor of quite a high % alcohol, always higher than that exiting the pot still. In this scenario, the thumper is a benefit, as it allows quite an enriching of the vapor to occur, with no additional energy required. The only condition is that the thumper is charged with a liquid of a reasonable % to begin with – if simply filled with water it won’t work.
To make the thumper effective you want
- Lots of vapor liquid contact, i.e. heaps of small bubbles – e.g. use a screen or simply lots of pinholes in the bottom of the inlet tube.
- The liquid in the thumper to begin high in alcohol, so a small volume of wash or, maybe better, tails from the last run. Recommending: You put tails or mash into the thumper – not water – and the loss is not a factor compared to the resulting alcohol content
- Larger is better than smaller. For sizing a thumper, see under
A good rule of thumb is to make the thumper twice the size of the amount of distillate in a single run. i.e.: one run = 1 liter of spirits then make the thumper 2 liters. As a minimum, have it at least 1/3 the volume, or if using tails in the doubler, (liters of wash * % alc. of wash + liters of tails * % alc. of tails) / 3). Many prefer to use a larger size to allow for condensation that always seems to overflow the thumper. One example with a still that was 250 liters and had two 50 liters thumpers as well as a 50 liter slobber pot.
Please note that thumpers are not the same as slobber boxes (although they look fairly similar. The inlet in a slobber box doesn’t extend down into the liquid, so no bubbling & hence further distilling takes place. Rather, it just provides a place for any rubbish (i.e. foam, mash etc.) pushed up the neck of a pot still to settle out before entering the condenser. They sometimes have a small drain cock on the bottom of them to help empty them while the still’s running. The original purpose for a slobber box was for stills heated by a fire beneath them – if the heating got too vigorous, and the contents foamed or bubbled up into the lyne arm, which it would settle out in the slobber box, rather than go and contaminate the main spirits being collected. They’re not needed on well controlled stills.
Double Walled Boilers
Single walled bottom still designs are good only for sugar mash distillation and unsuitable for distilling thick mashes or preparing absinth. With direct heating, and especially with internal heating of keg, local overheating can (and will) occur for highly viscous mashes (grappa, plum, apricot, apple, quince, etc.).
The decomposition (burning) of mash produces a terrible taste and smell, hard to remove. If you try to polish the distillate, the fruit taste and smell will disappear first.
It is a rather easy task to transform a keg to a safe, dual purpose, water bath type double bottom boiler. Generally a keg consists of the vessel itself; there is a lower and an upper skirt. Skirts are most cases welded to the vessel. If you close the lower skirt with a flat head (e.g. a 1,5 mm stainless plate) and patch the went holes, you get a lower vessel for the water bath. For joining the head TIG, MIG or stick welding is best, but brazing is also possible. Patching the went holes you may use welding or brazing.
Drill a 6 mm hole on the side of the lower vessel. Attach (braze) a 6 mm pipe to the hole and have it run vertically to the top of the keg. Lace it through the upper skirt through a went hole and bend it to a vertical position. Attach a proper safety valve (e.g. a weight type for pressure cooker) on the upper end of the pipe. When selecting the type of safety valve you have to consider the danger of implosion during cooling. At 180 degree from the 6 mm pipe (on the opposite side of the lower vessel) drill a 6 mm hole and braze over the hole a 6 mm nut. Close it with a heat resistant gasket and a 6 mm flat head screw. This will be the bleeder. Perform bubble tests on joints.
Filling: Remove the weight of the safety valve, screw off the bleeder. Fill up the lower vessel through the safety valve body and 6 mm pipe using a plastic hose. When water starts to flow from the bleeder, stop filling, reinstall safety valve weight, fasten bleeder screw. During distillation process water bath temperature will be in the lower vessel slightly above 100 Celsius due the minor overpressure, but this has no detrimental effect. Check the water level in the lower vessel each time before using, by shaking the keg. According to experience, refills are rarely needed. Annually descale lower vessels with vinegar. In case of using the keg in a cold climate, avoid freezing the water. The quality of distillate improves dramatically. Of course, if you distil thick mashes a greater opening (min. 15 cm diameter) is needed to fill and clean.
Gin head is a large separate compartment that sits above the boiler on a gin still in which the botanicals (juniper berries, coriander etc.) from which gin gets its unique flavor are placed and through which the alcohol vapor must pass before it enters the column. As such gin stills are pot stills rather than reflux.
They are still specifically designed for making gin although they are and can be used for making other similar drinks. As such they have mostly been made by one British company for the last two centuries although I dare say there are now other companies that make similar stills elsewhere. Steam or vapor distillation is better at extracting essential oils and other more soluble components as compared to steeping which tends to extract tannins, phenols and the more harsh bitter components.
. Still with a very large Gin head
A gin head is a pot or column that steam travels through enroute to the condenser. A thumper works rather well. Just pack it with the herbs and run clean drinkable 60% ethanol in your still for gin. Pack it with peppermint to make schnapps. Pack it with… well you get the picture. Put just water or varying amounts of ethanol in the still for making oils from mint or whatever has oil content.
One of the easiest ways to increase a heat transfer coefficient is to increase the velocity of the fluids. Temperature of the cooling medium helps, but velocity is MUCH better. This is why blowing on a spoon full of soup with your breath (about +32 C degrees) cools it off much quicker than holding it in front of your nose, even on a chilly morning. You get lots of heat transfer into your cooling water.
If you are going to bend copper: For larger diameters anneal the bend area, cool, pack with sand and form over wooden die that has been fabricated to match bend radius. This procedure will elevate the finished product above the amateur level.
Describing “shotgun” condenser
Some stills have a coiled vapor condenser consisting of 3m of 5mm tubing through which water flows, and from comments seems inadequate. What about using a mini shot-gun condenser? On a typical 50mm diam. column this would mean a 300mm length of 50mm tubing, with a plate on both ends with 12 holes drilled in a geometric pattern to take 12, 5mm open-ended tubes welded in place. It is still open to the sky for safety. On the side there is a water inlet at the bottom and an outlet at the top for the cooling water. In effect we have 3.6m of vapor in 5mm tubing surrounded by cooling water rather than the other way around. The unit can be welded on the top or attached by a standard 15mm threaded plumbing connector so that it could be replaced if necessary
Most hobby pot stills in the U.S. are made out of 20 liter pressure cookers (they have all the fittings you need including pressure release safety valves)- If this is in fact what is planned, you MUST remember to NOT PERMANENTLY MODIFY THE PRESSURE COOKER IN ANY way (remember, 10 mm copper tubing makes a nice coil, and fits the outlets on most stills!) if the law gets news about you running your own still- they can raid your place, if they find a pressure cooker with a bunch of copper tubing attached to it, and holes drilled in it that are homemade- they will have the evidence needed to take you to jail for running a still.
IF the pressure cooker is always returned to its original state (normal fittings and weights) after you distill with it, and if you put your condenser next to some beer making supplies (or, rather mash making supplies- same thing), when (if) the cops show up, they find a normal (unaltered) pressure cooker and something you will swear up and down is a wort chiller for the making of beer. If no moonshine is found- they have absolutely no case against you.
Second – The average 20 liter pressure cooker can be set inside a large stockpot, just measure the cooker, and go out shopping for a cheap canning pot big enough to hold it easily. By placing 2 pieces of wood, pipe, etc. across the top of the canning pot, the handles on the pressure cooker will sit on these cross pieces- this will keep the bottom of the pressure cooker off of the bottom of the canner. Fill the large tub with water and then fill the pressure cooker/pot still with your mash and cook with a nice even heat (if using gas this reduces the fire hazard as well- now the alcohol isn’t in direct contact with the metal touching the flame).
This allows you to distill mash that has a lot of solids (the more gentle heat helps prevent sticking and burning), it also allows you to do something else while warming everything up- Just put the water on to boil, and put the canner in after the heat is where you want it- better temp control- and unlike the still- you don’t have to watch the water heat up (unless you are bored out of your mind)- just make sure the pot still body isn’t touching the metal of the large stockpot – there you go- a homemade steam heated still!
Using a vacuum allows the use of lower temperatures, and can attain higher alcohol concentrations, e.g. at 42 mm Hg (cf 760 mm Hg = atmospheric pressure) the column only need be at 35 C (ie just use hot tap water to heat with). The azeotrope (the point where distillation ceases to work because the vapor and liquid purity are the same) moves towards 100 % as the pressure is lowered; below 0.1 atmospheres it disappears, allowing you to distill all the way to 100% alcohol (provided you beef the reflux ratio up to >20). That is also more energy efficient, and allows for a greater capture of the available alcohol. The lower temperature also means tless essential oils (which would be otherwise be broken down at higher temperatures).
The graph below shows the reduction in temperature. I’m not quite happy yet with my calculations for this – don’t go and design from it, but you can see the basic principle at work.
To create a vacuum, you can either use a mechanical pump, or a venturi ejector (water jet pump). The venturi ejectors (vectors) are commonly used by laboratories etc. to assist with filtering material.
Vacuum still, example;
Wash pot can be around 60L. It is enclosed in a rather large plastic barrel and I heat the system with hot water. The water is around + 80 C so I don’t need a lot of it and. The column is 2″ X 60cm Stainless Steel packed with ceramic rings. The water for the ejector goes straight through so as not to create resistance on the out end. The cooling water inlet at the bottom end… The ejector suck out from collecting jar which is in turn connected to the condenser so any vapor rising up the column has to go through the condenser before it gets to the collector before it gets through to the source of the vacuum. The cold water in north areas can be somewhere around +4-5 C so cooling then is not a problem.
Note that in most cases, the vacuum is applied to the distillate collection container, after the condenser. This way there is little loss of vapor from the process, and there doesn’t need to use much vacuum. Many of the comments below are concerning the setup where the vacuum is applied to the vapor line.
There are several problems with Vacuum stills though:
- you can lose some alcohol vapor out through the vacuum pump,
- you must have an accurate measure of the vacuum applied (not a big problem, one of the reasons the still is not easy to build),
- it’s hard to find leaks (thus requires care during construction),
- very low vacuums are difficult/expensive to attain (but generally not required – only a small vacuum is needed), and
- the low temperature can make it difficult to recondense to vapors (need really cold cooling water & enough condenser surface area)
Often the vacuum can be made by using a “Venturi” or “Vektor” which uses the cooling water, and causing it to go through a small nozzle increases its velocity. This causes a corresponding decrease in pressure, and hence can “suck” vapor from the still. However, this can eject some vapor out of the system.
The heating can be a simple water jacket around the pot, using hot tap water.
What can also be confusing is when the mash begins to boil, the vapors will expand into the vacuum space, and your gauge may go back to zero. This doesn’t mean you’ve lost your vacuum, but if you can have some of your still appliances in glass or plastic so you can see what is going on, this helps so you know you have some action and not a leak.
One of our visitors is in the process of working on an improved vacuum still design. We’ll keep you posted once he’s happy with the results (including maybe a photo, design, info, history & performance.)
It is good to go for a batch method where the still, condenser, and receiver were under vacuum; cooling would be circulated car antifreeze which was cooled with an ice/salt mixture. The condenser would be a multi tube high surface area low volume of copper, the salt/brine would attack the copper hence the car antifreeze. This would give a nice big temp change. The pump would only have to maintain the vacuum so it could be a smallish piston perhaps a good diaphragm might do. The exhaust routed through a secondary condenser although I wouldn’t expect much if the primary condenser was doing its job, the receiver could sit in a bucket of ice/water to stop any secondary boiling.
Another way of cooling would be to use a freezer, make a dummy door “if you want the freezer after” with a couple of holes in it, inside have a tank of antifreeze and circulate this through the condenser, it could run as low as -18 C. Any condenser after the vacuum pump would only have normal cooling as it would be at atmospheric pressure.
Tip if you’re going to make a multi tube condenser these hints may save you some time. The endplates can be cut from sheet copper or a piece of tube opened out. Cut a circle out about 0.5 inch diameter larger than the tube.
Find a socket from a car socket set about 3mm dia. less than the bore of the outer tube, trap the annealed copper disc between a 6-7mm thick metal plate in a vice, and beat the edge of the copper over the socket. With dividers find the center of the disc on the inside not out.
If you use a 32mm bore copper tube seven 10mm pipes will fit in nicely.
Draw the 7 circles evenly spaced. Don’t try and drill the holes! It’s disastrous! Just drill a very small hole and use a metal cutting fret saw or even better a jeweler’s saw – if you have one. Make two plates. Silver solder or use the copper/phosphorus rods to solder the 7 tubes to the end plates, then slip the unit inside the outer tube, solder in place, make end plates to reduce the size down to a more convenient suggested something like 22mm.