In general, we don't encourage our distillers to lose their heads, except for one very specific time. (Oh, and we also suggest chopping off a few tails too.) Let me explain.
In the world of whiskey creation, there are four parts to the distillation run.
Once fermentation is complete, it's necessary to heat your wash to boil off the ethanol and separate it from the water that will be left behind. While most people know that ethanol is what we're after in terms of creating whiskey, many don't realize that there are other compounds that will escape in the heating phase – and not all of them are desirable.
The first of these undesirables are known as foreshots. This initial part of the run contains methanol, a compound that can cause death or blindness, so it should definitely be discarded. Fortunately, the foreshot only comprise about five percent of the total run.
Next comes the portion of the run referred to as the heads. While the heads aren't as fierce as the foreshots, they smell pretty awful – kind of like the stuff you'd use to clean a paintbrush. That's because they actually contain solvents like acetate, acetone and acetaldehyde. So here's where we recommend that our distillers lose their heads, and set this portion of the run – about 20-30 percent – aside.
With the caustic stuff out of the way, the road to fine whiskey finally smooths out. This part of the distillation process is known as the hearts – and for a good reason. The hearts offer a lot to love – flavor, a touch of sweetness and the warm smoothness that is the hallmark of all good whiskey. It should be highly valued (and saved) as the liquid gold that it truly is. You can expect about 30-40 percent of the liquid created during the distillation run to be hearts and you'll know when your still is producing hearts because the harsh smell will disappear.
If you've ever tasted some less-than-fine whiskey, you might have exclaimed that it tastes like fuel. No doubt, that's because it had to much of the tails in it – the portion of the run that comes after the hearts, as the drinkable alcohols have already been distilled and alcohols with higher boiling points are released. These include butanol and propanol, so they are fuel in a very real sense. The whiskey from this part of your run will taste thin (and fuel like) and can be spotted by an oily sheen on top of the distillate. It should be collected and set aside because, like the heads, it still contains ethanol and can be added to future distilling runs.
Knowing exactly when to "cut" the distilling run between the foreshots, heads, hearts and tails distinguishes an accomplished distiller from an amateur. If you distill long enough, you'll eventually get the hang of it. But fortunately there's no need to leave things up to guesswork because – as with much of distilling – science comes to the rescue. Monitoring temperature can be a good guide to getting things right, as we explain in this post (this will link to the next post about cutting).
Posted by Jason Stone on