This page is intended to educate a pot still novice about the different fractions in a distillation run, and to help them learn how to make cuts between them. While it is focused on pot stilling, reflux still operators will also need to have the same basic sensory skills, especially to determine the heads cut. The tails cut is done mainly by temperature rise in a reflux still, and you should refer to your specific still types instructions.
Cuts is the term used by distillers to describe the process of deciding which portions of the run are to be included in the final product. Making good cuts is essential to making a good spirit; it can mean the difference between a cheap, hangover-inducing swill and a top-of-the-shelf product.
Cuts and Fractions
Cuts are the points in a distillation run where the distiller separates the distillate into separate fractions (divisions between sections of the run). In general distilling talk, cuts and fractions have generally been referred to just as "cuts" using the same term for both the cut points and sections of a run (i.e., the "cut to hearts" and "the hearts cut" are different things), although in this article the two will be treated as separate terms to avoid confusion. In order to make good cuts, it is important to understand what the different fractions of a run are, and how to recognize them. Cuts are generally divided into four fractions: foreshots, heads, hearts and tails. They are not hard divisions. Smearing, the mixing of the fractions, causes all four fractions to flavor the whole run. Most spirits are distilled at least twice. The more a product is distilled the more compressed and distinct the fractions are. The negative is that it also reduces that flavor of the spirit.
Procure a good number of small (say 500ml) jars, number them, and get a big ol pot that is big enough to hold everything you'll want to blend. Collect your run in these numbered jars, and leave them to air out for a day or two with a coffee filter or similar over them to keep out the bugs and dust. Some of the more volatile and unwanted components will evaporate off over this time, and you'll be able to make better cuts and blends.
Learning the Cuts
- For one excellent discussion of cuts during a rum run in a pot still see this post:Novice Guide for Cuts (pot still)
The best way for newbies to learn to make cuts is to collect everything from the run in small glass jars, let them sit covered by a paper filter overnight, and then smell and taste each bottle in turn. With more experience, distillers can learn to "cut on the fly", making cuts during the run.
Once you know your equipment and your mash, fractions are fairly predictable. The ABV% will drop (and temp will rise) over the course of the run, and this is one indicator of cut points that can be used as a crutch to judge with. However, temperature and %ABV are not recommended as a guide for cuts. Vapour temp is directly related to %ABV, just basic physics. If you know the temp you can reliably predict the %ABV, and vice versa. They tell you the same information. For example, 20% ABV output = 98°C. There is a chart for converting temps to %ABV and a more detailed discussion of this here
There is an issue of reading the temp correctly, ie in the right place, at the very top of the vapor path, just where it turns down into the lyne arm / product condenser. But that is a very minor design detail compared to the unreliability of thermometers.
Temp is no worse than %ABV for deciding where to make the cuts, but both are rough guides at best.
Cuts should be ultimately made by taste and smell, not %ABV or vapor temp.
When do I start collecting?
Once you collect and remove the foreshots you can start collecting product. The initial heads are fairly stinky nasty stuff. Don't drink them as they will cause your tongue to go fuzzy and numb. You'll find that out because you're curious and you're going to ignore that advice and do it anyhow. Don't worry, everyone does it.
When do I stop collecting?
If you are collecting in jars, go until the distillate starts to get cloudy. This will be deep into the tails. This is good for both stripping and spirit runs. If you're doing a stripping run into a single jar stop at the same point. For a Spirit run you into a single jar you will need to know how far into the tails you want to go. This is not a good start for a newbie. Wait until you understand cuts better for that. Some distillers only collect in jars as it makes blending later on easier.
Stripping or Wash Run
The stripping run begins the separation of the ethanol from the water. Here you can make a Foreshot cut, but no other cuts are needed if you are planning a second Spirit run. There's no need to collect into jars here, one big container is fine. The output of this step is referred as Low wines. All of that will be put back into the still at a later date for the spirit run.
This is where you do a Foreshot, Heads, Heart, and Tail cut. For a spirit run the Heads and Tails are more compressed into the end jars. If you're collecting into jars you do not need to make cuts during the run. You will do that part later by selecting the jars you want to keep.