Some high-end cocktail bars around the world, and even some spirits brands, employ a sophisticated piece of science equipment called a rotary evaporator, or rotovap (sometimes spelled rotavap), to create flavor-focused cocktail components via vacuum distillation. The equipment first made it out of the science lab to grace high-end restaurant kitchens, and now bartenders are building on the tool’s culinary applications to distill drink ingredients.
Its effects, although notable, are subtle. Unless you’re a top bartender, a serious cocktail enthusiast or perhaps Bill Nye, it’s possible you didn’t appreciate, or even notice, what went into producing your drink. It’s also possible you haven’t encountered rotovap-produced ingredients yet. They’re not common; aside from the rotovap being a complex piece of culinary technology to use, you also won’t see it around too often because of its price. Most bars don’t have the funds to shell out upwards of $11,000 for the full rotovap setup.
However, an increasing number of upper-end bars are choosing to invest in this sophisticated piece of equipment. They’ve decided it’s worth the cost to produce better and more interesting cocktails. This is how and why they use it.
How a Rotovap Works
While traditional distillation purifies a liquid (fermentation) by heating it up to evaporate and cooling it down with a condenser to reclaim the distilled vapors, a rotary evaporator uses a gentler method to achieve a similar outcome. In a nutshell, the rotary evaporator lowers the pressure of the sample’s environment using a vacuum, which lowers the boiling point significantly. “There’s no oxidation,” says Dave Arnold, the co-owner of New York City’s late Existing Conditions and an expert in culinary technology. “Unlike standard distillation, where you are trying to concentrate alcohol and reduce unwanted contaminants, with roto-evaporation, you are trying to capture all the volatiles from the flavor you're looking to distill.”
This means that the final product is clean and fresh, unaffected by the flavor-killing effects of too much heat, which is particularly beneficial when working with ingredients such as fruits and herbs. Simply put, the rotovap technology has the potential to capture the essence of the raw materials and flavors of delicate ingredients that traditional distillation cannot. It evaporates the solvent, separating the liquid from the solids, meaning that rotovaps can “de-wood” spirits—remove the tannins imparted to spirits during the aging process—and even remove the color, spice and bitterness of ingredients as well. In culinary applications, chefs typically use this piece of equipment to harvest the solid portions of ingredients, but bartenders are more interested in extracting the evaporated solvent.
Rotovap’s Use In Cocktails
The rotovap has a large number of applications in cocktails, but essentially it’s used either to add flavor or to remove undesirable characteristics of an ingredient. “This machine is excellent at capturing and preserving the aroma of spices, herbs and other ingredients but really specifically with the fresh herbs,” says Arnold. “When using a rotovap, you're really preserving the delicate and fresh flavors that would otherwise be lost if you dried them out or applied heat to them.”
Alex Kratena at Tayer + Elementary in London uses the rotovap to flavor alcohol with notes that interest them but aren’t widely available as commercial products. “For example, our ready-to-drink Sandalwood Martini contains a distillate of sandalwood that brings a very distinctive, soft, warm, precious wood scent to this amazing classic,” he says. At The Connaught in London, the bar team uses the rotovap to create bitters and tinctures incorporating various herbs and spices, which they present to guests as options for the bar’s renowned tableside Martini service.
The team at Artesian, at The Langham hotel in London, created a cocktail for the bar’s “minimalist” menu—in which each drink contains only two ingredients and which relies heavily on the rotovap—made with cognac and green coffee. The drink is served over a perfectly clear ice cube as a crystal-clear liquid, the color and tannins removed from its ingredients, but its flavor is distinctly that of coffee and cognac.
“At Existing Conditions … we've done one drink with habanero where we were able to eliminate the spice,” says Arnold. For imbibers who love the taste of peppers but can’t handle the heat, the rotovap allows the bar team to create uniquely flavored distillates and cocktails.
Similarly, at Empirical Spirits, a flavor-focused microdistillery in Copenhagen, the team uses large-scale low-temperature distillation to extract the essence of theingredients they source, one being the rare Mexican chile, the pasilla mixe, from which they make the Ayuuk spirit that tastes of smoke, earth and dark red fruits, leaving out the spice.
Porter’s, a microdistilled spirits brand, uses a rotovap to flavor its gins. “We use it to layer delicate notes on a classically distilled gin base,” says Alex Lawrence, a co-founder of the gin brand and the global bar director for the Mr. Lyan group of bars. “But we've also experimented with it both seriously and light-heartedly. It's great fun to create single-note ‘vodkas’ and redistilling spirits or cocktails to use as modifiers in unexpected ways.”
Lawrence says that the rotovap is great for splicing textures and also for extracting unexpected flavor extraction from things such as minerals, barks and intense fruits. Prior to joining the Mr. Lyan team, he was at Orchid in Aberdeen, Scotland, where a rotovap also was employed. “Our Battered Mars Bar Old Fashioned needed a clean extraction due to chunks of fat and grease not being delicious,” he says of the Orchid team’s concept. “The distillate provides a classic Rum Old Fashioned with an indulgent funk that’s enjoyable without clogging your arteries.”
We’ve mentioned how several bars use it for distillation. You’d be forgiven for wondering about the legality. After all, distillation at home or at a bar is illegal without a license. However, if you’re using alcohol that you purchased and paid taxes on (which is the main reason why home distillation is illegal, the safety precautions being an afterthought) then using a rotovap to manipulate those ingredients falls into a gray area where a case could be made for its legality.
Some bars simply use water distillation, but water doesn’t extract flavor from ingredients the way that alcohol does, so it’s not always worthwhile. Water also has a higher boiling point than alcohol does, so it takes more time and energy to distill, rendering it a vastly less appealing option. That said, for all the straight-edged folks that don’t want to walk that fine legal line of alcohol distillation, water distillation is an option.
Finances are another factor to consider. With new rotovap setups costing upwards of $11,000, you’ll want to make sure that, first of all, you know how to handle the equipment to prevent breakage, and second, you have (or can obtain) the knowledge to make the best use of the equipment to truly get your money’s worth out of it. “For instance, many rotovaps come standard with a small flask, when for bar purposes you really need it to have a three- or four-liter capacity,” says Arnold. “So not only do you need to buy a bigger one, but then you should probably also spend a little extra to get a plastic-coated flask so that if it breaks, glass doesn't go flying everywhere. Less-expensive units that circulate ice water to cool everything down will run you a couple of thousand.”
The rotary evaporator itself, on average, costs about $8,000, and then you have to spend another $3,000 or so on a chiller and another $3,000 on a vacuum pump. It’s a worthwhile investment for bar owners that want to build a unique high-end bar program but not a piece of equipment to buy just to have it. Arnold advises, “[I]f you're looking to get one, I recommend you meet up with someone who already uses one; it’s best to try that way.”