How centrifuges, rotovaps and liquid nitrogen found their way out of the lab and into your glass.

When you imagine a bartender, you might picture someone dressed in suspenders, gold sleeve garters, an un-ironic curled moustache and maybe a top hat. Stray just an inch from the CBD and that archetype shifts slightly. Vintage button-ups, heavy-stickered tattoos, mullets and some sort of filthy facial hair (think ’70s porn). And we love it all. What you don’t expect to see is a mad scientist-style bartender operating medical equipment, fiddling with beakers and ferments, but it happens, and it’s happening more and more, too. So, let’s break it down.

You’ve heard of molecular gastronomy – enzymes, dry ice, foams, all that very fancy stuff that chefs like Heston Blumenthal have pioneered. But have you heard of the cocktail equivalent, molecular mixology? Picked up in the early 2000s, the premise of molecular mixology was fairly similar to Heston’s complicated food experiments, taking singular or molecular-level flavours and reproducing them in a way that’s intriguing and different. Dave Arnold, a food scientist and innovator, fronted the movement, even releasing a book that’s become a cult bartender favourite, Liquid Intelligence: The Art & Science of the Perfect Cocktail. It was an interesting, new way of looking at bartending, and what cocktails taste like and mean. Since then, despite the return of the classics, the art form has taken off, with more bartenders experimenting with different forms, clarification methods and ferments – dropping the daggy 'molecular mixology’ tag along the way. For bartenders these days, it's not enough to just nail the classics (though this is really important), they also need to have a clear understanding of these sciencey practices and how to apply them to the craft. Things like clarifying, aromatising, foams and rotovapping. Let’s have a gander at some of these alien practices.

Centrifuge clarification

We’ve talked about clarification before, even sharing a very popular Clarified Piña Colada recipe, and it’s true, this isn’t a new practice, but clarification via centrifuge is. So, what is a centrifuge? Essentially a centrifuge is a device that lets you spin liquids at super-high speeds, using centrifugal force to separate a substance into its various parts. On a large scale, a centrifuge can simulate high gravity or acceleration environments – for example, in G-force training for pilots. An everyday example exists in your washing machine to draw water and particles out of clothes. For bartenders, the centrifuge is just a much easier and faster way to clarify a cocktail or its components, drawing the solids out of the liquid to leave you with a clearer drink. Though centrifuging for clarification started as a very niche and innovative technique, it’s now commonplace. By applying huge amounts of force (several thousand times the force of gravity) to a liquid or puree, the bartender can force it to separate. All the gritty sediment and particles fall to the bottom making a kind of mash. The oils float to the top and what’s left in the middle is your liquid, clarified gold. Like clarifying dairy with an acid, this process is faster, better and can be used more broadly. Dave Arnold was a real instigator of this method and now sells his own centrifuge via his company Dax and Booker.

Liquid nitrogen

Ah, yes dry ice. The dangerous but fun party prop used by the most bougie primary school discos. It’s an ingredient that can be used to do some cool things, but also has the potential to do enormous damage. So, for this, we issue a warning: DO NOT TRY THIS AT HOME. If you muck around with it or try to drink it, it will freeze your oesophagus and that is, obviously, no bueno. For bartenders, dry ice or liquid oxygen is used to instantly freeze ingredients or chill glasses – snap-freezing. An example of this would be snap-freezing a herb with liquid nitrogen to retain its brilliant flavour and colour. You can then muddle it without the herb bruising and, once strained off, you’re left with an ice-cold, stunningly green, fresh cocktail. Also, you get to play mad scientist with all the clouds wafting from the glass.

Foams

Everyone loves a good foam. They smell intriguing and add a seriously interesting texture to your drink or food – it’s a cloud-like, melt-in-your-mouth experience. But making a foam from scratch isn’t exactly a walk in the park. For a foam to work, there needs to be a reaction between nitrous oxide and a protein, which can be egg whites, agar agar or gelatin. Essentially, what happens is the nitrous oxide forces the protein strings to unravel, creating these foamy structures that hold the gas. If this all seems really freaking sciencey, that’s because it is. However, if you’ve ever worked at a cafe or even used a cream whipper at home, you’d be familiar with it, perhaps without even knowing. To create a foam, a bartender uses this same instrument, but instead of just using cream and nitrous oxide, they’ll add their proteins (whatever they may be), a flavouring (or a few), and sugar to the whipper syphon. Once that’s screwed in properly and not overly full (there are a tonne of risks associated with this device) the nitrous oxide cartridge is screwed in. When you hear a slight pop, that means it’s released. You have to shake it quite thoroughly and place it in the fridge before using.

Rotary evaporator

In terms of big-deal bartending equipment, this is Ron Burgundy (“I’m kind of a big deal”). Not just because of its absurd price, but also because of its versatility. The rotary evaporator or ‘rotovap/rotavap’ is a hefty instrument consisting of a heating bath, glass bulb or flask, vacuum system and condenser. To give you an idea just how sciencey this thing is, it’s traditionally used in chemical laboratories to gently remove solvents from samples by evaporation. ‘Gently’ is the operative word here. This method of evaporation without overheating piqued the interest of our molecular gastronomy and mixology geeks, who saw its unique potential to not only clarify (like the centrifuge) but also impart the hardest and freshest ingredients to distilling and cocktail making.

What do we mean by this? Well, in traditional distilling, you need to heat the ingredients to a very high temperature to capture the vapour. When this happens, your botanicals cook. All herbs – basically all fresh ingredients – will wilt and you’re left with that cooked flavour. The rotovap still needs to be heated, but only to about 30 degrees in a vacuum, meaning those bright and fresh ingredients will not cook. For example, you could make your own fresh cucumber and coriander spirit without it being boiled and tasting boiled. The rotovap can also “de-wood” your spirits, which is to say it can take out tannins imparted from aged spirits and remove colour and other harsher flavours like bitterness and spice. You can understand why this is particularly revolutionary for cocktail bars. The ability to remove or add flavour that is usually diluted due to heat or drying is extremely exciting. Say you wanted to make a Mojito without the muddled mint. The rotovap can infuse the rum and the mint, so you have a lovely clear drink that can be poured straight or over a big hunk of ice.

Where to start

Many of these techniques require expensive equipment, so if you don't have access to a high-tech kitchen, it'll be hard to try them for yourself. But for a lo-fi way to experiment with some more advanced methods, try fat washing! Our Bacon-Washed Old Fashioned recipe is the perfect place to start. And keep an eye on your bartender next time you hit up a fancy cocktail bar – you might catch some of these techniques in action.