What Kind ofStill

Pot Stills

Pot stills were the earliest kind of stills. They simply had a pot to boil the fermented mash in, and an output tube that passed through something cooler (air or water etc.) which condensed the vapors coming from the pot.

The copper pot stills like the ones shown are reputed to have been in use for over 500 years to make some of the finest Irish Whiskey in the world. While the pot still is enormously inefficient, it is uniquely simple and easily adapted for home distillation of everything from essences to whiskey and moonshine.

From the Irish Whiskey Trail

Little has really changed in the design of the pot stills over the last 2000 years.

You won't find much difference between the moonshine still shown below and the alembic pots used years in Egyptian times to make perfumes.

Pot Still Distillation Perfume

From the Irish Whiskey Trail

Home Distillation
From the John C. and Olive Campell Collection Southern Historical Collection, University of North Carolina

The problem with pot stills is that they don't do a good job at separating out exactly what you want to distill as output. They are usually used to separate compounds whose boiling points differ by about 100° C. When beer is distilled, lots of things come out, some good, some bad. And because there are no fine controls on this kind of still, the output contains a lot of impurities.

Nevertheless, after each distillation, you always get a better output product from that which you started with. So each time you redistill the output in a pot still, it will come out a bit purer, but you lose a little each time you redistill. To make it really pure, you have to distill it so many times that you'll end up with almost no output.

Along those lines, If you are distilling fermented sugars with a pot still, unless you re-distill the output several times, you can get a massive hangover if you drink whatever comes out. Hangovers are caused by the impurities in the alcohol. In short, you've been poisoned (but just a little bit)!

Because of this limitation, it takes a lot longer to produce a reasonably pure finished product using pot stills. I'm told the finest Irish distilleries still use pot stills to make their whiskey. They take great pride in the fact that they triple distill the whiskey. The demand for this product was so great, that they built huge pot stills, some holding over 30,000 imperial gallons of beer.

So, while it is tempting to take the easy way out and build a simple pot still, it really wouldn't meet our goal of producing the very purest spirits, in the most efficient manner. To do that you've got to think about a reflux still.

Reflux Stills

The pot still was the only distillation method known for almost 2000 years. But that all changed with the introduction of the reflux tower the late 19th century. That invention revolutionized the production of many valuable petroleum and chemical products that we commonly use today.

Basically, the reflux still is a structure that allows the distillate vapors from a boiler to rise up a column to the top where the vapors are condensed. The condensed liquid is then allowed to run back down through the rising vapors to a point where the temperatures become hot enough that it boils again. This process is called refluxing.

As this cycle continues, the mixture inside the tower is effectively re-distilled. In the process, the components of the mixture separate into discrete layers within the column based on their boiling points.

Industrial distillations are carried out in huge towers, where the refluxing is continued until the mixture to is completely separated into layers. At that point the different components can be simultaneously drawn off the layers within the tower almost as fast as the mixture can be introduced into the column. This method is called continuous distillation.

While continuous distillation methods provide the volume output demanded by the petroleum industry, the practice is not well suited to our interests. We just want to separate on occasion, a single compound from a liquid mixture with a small scale still. That's called batch distillation.

Fortunately, the reflux column can be used with either batch or continuous distillation operations, and it can be scaled up or down to meet either industrial or home distillation needs.

How this scaling is done directly affects how we build our home still. So to do it right, we need to understand what is going on in the process.

The best place to start on that is to look into what happens when you boil something in a reflux column.

Batch Still And Distillation Column

Boiling Beer

There is a lot of terminology surrounding the art of making Beer, Wine and Spirits. We are not going to get into most of these terms because they are not central to the construction of a still.

But to keep things straight in this manual, we'll be talking about Spirits as a product that is made by boiling Beer and condensing the vapors (distillation). Beer, in that context, is the result of fermenting Mash, and Mash is simply a mixture containing sugar.

Fermented mash (beer) is typically made up of ethyl alcohol and a lot of other things that most folks don't want in the distillate.

If you are going to use the still to process a batch of spirits then you first heat the beer enough to boil off most of the more volatile components (heads), before you collect the spirits.

What's really going on in the still when you boil the beer looks something like this:

Ultimate Home Distillery

The coolest part of the tower is at the top, and the warmest nearest the heat source at the bottom.

The beer components that have boiling points over 100° C will mostly remain in the boiler. For that matter, you won't let the temperature in the column get over 80° C. This will keep most of the undesirables (called tails) out of the distillation output and in the boiler. You would also throw away all of the distillate that comes out before the temperature reaches 78° C. This part is called the heads, which contains methyl alcohol (a poison), and some other non-desirable congeners such as Ethyl Acetate.

So the important thing to remember about this process is that the mash you start with might be simple (sugar, water, yeast), but after fermentation, the beer contains all the ingredients shown above, and more.

It's also important to recognize that some of these compounds (e.g. methyl alcohol, 2-Propanol) have boiling points quite close to the ethyl alcohol you might be trying to distill out. That means you will have to be careful about controlling the column temperatures to make sure that you collect only pure spirits.

All these things considered then, the reflux still is by far the best choice. It will allow you produce a much better spirit than the pot stills.

Admittedly, this kind of still takes a bit more thought at the design stage, but really that's what we're talking about now.

So now it's time to go a little deeper into the issues that will come up in actually building a small-scale reflux distillation apparatus.

Fractionating Reflux Still

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  • codi
    How to make alcohol distillation apparatus?
    8 years ago
  • rowan
    What kind of pot to use for distilling alcohol?
    7 years ago
    What happens in a distillation column when you're condenser doesn't condense?
    7 years ago
  • Zahra
    When home distilling water what gradient to throw away?
    7 years ago
  • Hanna-Mari
    What kind of whiskey still is best?
    6 years ago

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