Bubble-Cap Stills Suck at Making Whisky!

Introduction

There, I said it. I have long considered not writing this post, but the misinformation about this topic affects the craft distilling industry negatively. That needs to be amended. Sure, statements like this will make me some haters, but hopefully that will be compensated by more craft distillers now being able to make better choices. And more importantly: better whiskies.

In this iStill Blog post, I’ll first investigate what a whisky is, and what its flavor profile should be like. Then, I’ll dive into the bubble-cap still design and elaborate on its pro’s and cons. Finally, I’ll explain how the bubble-cap still design prevents the craft distiller from making great whisky.

What’s whisky?

“Whisky is a distilled spirit, made from grain, where one – while drinking it – can identify the grain the whisky is made from”. Don’t you just love the above definition? It so clearly explains everything a whisky needs to be. Made from grain. And with the flavor profile intense enough to allow the drinker to establish the exact grain base. A spicy whisky? Probably rye. A sweet kinda whisky? Corn, so maybe a Bourbon. A mellow whisky? That must be a whisky made from wheat. A complex, full bodied whisky? I am putting my money on malted barley as its grain source.

Grain flavor profiles – and therefore whisky – are quite unique in that they offer front-of-mouth, middle-of-mouth, and back-of-mouth flavors. The floral and fruity flavors can be distinguished in the first second, where heads blend into hearts. The generic grain flavor hits you in the middle of the hearts cut, right after the headsy flavors subsided. The long finish reveals the tails-associated earthy, rooty, and nutty flavors. It is this long finish that is essential to whisky; essential to bringing out not only a long-lasting taste experience, but also the flavor identifiers for the grain bill.

What are the design pro’s and cons of a bubble-cap still?

A bubble-cap design is basically a potstill with two kinds of obstructions in the vapor path. First (from the perspective of the rising vapors), there are the plates with the bubble-caps on them. The gasses need to travel through them. Secondly, the vapors hit a cooler (that is often called a dephlagmator). The plates hamper the free flow of vapors. The cooler liquifies part of the vapors. The liquids fall back on the plates, creating a fixed liquid bath on ‘m. The gasses now have to almost fight their way upwards: through the plate, through the liquids, and through the cooler.

The benefits? Where a potstill can perform only one redistillation cycle, a bubble-cap plated still can perform multiple distillation cycles in one run. No more need for a stripping and finishing run! That’s great news. It helps with time and energy management.

The drawback? Those fixed liquid baths on top of the bubble-cap plates are tails traps. Now, mind you, this isn’t a drawback when producing fruit brandy. Fruit brandy focusses on heads associated flavors. For those fruity flavors to shine, tails smearing (with its heavier flavors) must be prevented. The bubble-cap still was invented for fruit brandy production. Bubble-cap stills offer a great defense against tails smearing. That was the real innovation they brought about, over a century and a half ago. Good for fruit brandy. Bad, really bad for whisky!

Why do bubble-cap stills suck at making whisky?

Bubble-cap stills suck at making whisky because they create two-dimensional spirits, drinks that high-light front-of-mouth and middle-of-mouth flavors. Whisky is (or should be) a three-dimensional drink, that offers a front, a middle, and (most importantly) a back-end.

Over 50% of the flavor is tails associated, is rooty, nutty, and earthy in make-up. It is that third and last dimension that makes or breaks a whisky. Try it. Drink some single malt. Wetten your mouth with a sip, then swallow. Keep your mouth closed. Now start counting. How long do you taste? Where do you taste it? A good fruit brandy is gone in seven seconds. A good whisky lasts and lingers in your throat for 15 to 25 seconds. The difference? Whisky has (or should have) a back-end, fruit brandy shouldn’t.

This is why bubble-cap stills suck at making whisky: they prevent the very flavors, that define any good whisky, from coming over into your spirit. Now that you know it, you can make better purchasing decisions, when starting-up (or reconfiguring) your distillery. Do you want to learn more about stills? The iStill Distilling University teaches you all there is to know about still design. For more information or course registration, please reach out to Veronika@iStillmail.com.

Bubble-cap plate …

Bubble-cap still …

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