For some basic information on liquid nitrogen and dry ice, including some vital safety procedures, see the Equipment section, here. Don’t use these materials unless you know what you are doing, which means you have been trained by someone with practical experience and you feel very comfortable with the materials. Reading this book does not constitute adequate training. Never, ever serve a cryogenic agent such as LN or dry ice to a person. When you serve a drink prepared with a cryogen, the cryogen itself must no longer be present—just the chilling effect. Safety mistakes can end your life or the life of someone around you, and the mistakes aren’t always obvious.
LIQUID NITROGEN
Liquid nitrogen is what it says it is: liquefied nitrogen. It is −196°C (−321°F) at atmospheric pressure. Liquid nitrogen constantly boils off into nitrogen gas, which joins the atmosphere—of which nitrogen is already the major component. Now, you can chill a cocktail with liquid nitrogen. It is fairly easy to tell when all the nitrogen has boiled off and you aren’t in danger of serving someone liquid nitrogen by mistake. But chilling cocktails with LN is problematic.
If you don’t agitate liquid nitrogen it will just float on top of your cocktail, creating a frozen crust without chilling the bulk of the drink.
Even though liquid nitrogen is absurdly cold, every gram has only the same chilling power as 1.15 grams of ice: it takes more LN than you expect to get any real chilling done. On the flip side, if you add too much, you will make things dangerously cold very quickly. Liquid nitrogen floats, so you can’t just pour it on top of a drink and expect it to chill. The LN will float to the top and create a frozen crust on the liquid, leaving the bottom unaffected: not what you want. Stirring is ineffective at getting the LN to really mix in well unless you stir vigorously, which is difficult, because as you mix LN with relatively warm liquids, it boils violently, splashing cocktails everywhere, getting LN all over your arms, and making so much fog that you can’t see what the hell is going on. For all these reasons, I don’t recommend chilling individual cocktails with LN. LN is useful for chilling large batches of cocktails, with a technique I call rock and roll.
Rock and Roll: Get two large containers, larger than you think you need.
They should each hold more than four times the total amount of cocktail you are going to chill—preferably six times. If the containers are made of stainless steel, never touch them with your bare hands while you are chilling or you risk frostbite. If you use plastic containers, be careful not to leave the liquid nitrogen stationary in them too long, or they’ll crack from the cold. Don’t ever use glass—it might shatter. I usually use plastic and take the chance on cracking.
Rocking and rolling drinks with liquid nitrogen.
Pour the cocktail into one of the large containers, and pour about two- thirds of the cocktail’s volume’s worth of liquid nitrogen on top. Quickly (remember, we don’t want plastic containers to get brittle and crack) pick up the container and pour the contents through the air into the second container. Nitrogen fog will be everywhere. Quickly pour the mix back into the first container. Keep going back and forth, rocking and rolling the drink between the two containers until the fog stops, which is your indication that the LN has evaporated. If you have added too little LN, the drink will be too warm; add more LN and repeat. If the drink is too cold (as in, it has solidified), run tap water over the outside of the container while stirring the slush. It will melt quickly.
If your rocking and rolling sprayed cocktail everywhere, making a king-hell mess, you either have terrible aim or your containers weren’t big enough. Remember, I told you to get bigger containers than you thought you needed! Trick: if you sense that the cocktail is about to boil over and make a mess—and your senses will get attuned to such things—simply stop midpour and begin pouring only half the contents back and forth at a time until the boiling calms down. Pouring only half reduces the amount of mixing and therefore the violence of the boiling as well.
When I chill this way, I’m usually making a lot of a particular drink that can’t be made with typical shaking techniques. Batches of cocktail for
carbonated drinks, for instance, are often rock-and-rolled. Ditto drinks that you would use the juice shake for at home. Be careful not to overchill your drinks. They’ll taste bad and you’ll burn someone’s tongue. If the drink is a solid, it is way too cold. If the drink is merely slushy, you won’t hurt anyone, but the drink will be colder than optimum.
VISUAL CUES TO CHILLED DRINKS (LEFT TO RIGHT): 1) This cocktail is so cold it will likely be
painful to consume. 2) This cocktail won’t hurt you (unless you drink it quickly) but it is too cold to taste balanced. 3) This cocktail is still too cold for a cocktail with oaked spirit, but is good if you know you won’t serve the drink for several minutes. 4) Ready to drink.
Liquid Nitrogen for Glasses: There is no better way to chill glasses than
with liquid nitrogen. It feels great, looks great, and chills only the part of the glass where the drink will be, avoiding the base and stem and thereby the sweaty ring on your table. Keep an open vacuum-insulated thermos full of LN behind the bar. It will last several hours. Pour a little LN out of the thermos into a glass and give the glass a swirl, as if you are observing a fine wine. In several seconds the glass will be cold. Pour the extra LN back into the thermos, onto the floor, or into the next glass you need to chill. In a few seconds the glass will frost over most appealingly.
A perfectly chilled glass.
But remember, this is LN, and there are some less-than-obvious safety rules to observe. Never chill a glass in front of a person’s face. If you inadvertently spill LN or the glass cracks, he or she could be injured. Never chill glasses over open ingredients or over an ice bin, lest a glass break and ruin your products.
Choose appropriate glassware. Only use glasses that curve in toward the lip, such as champagne flutes, wineglasses, and coupes. Don’t try martini glasses: when you swirl, LN will spray out of the glass and could get in your eyes. Some glasses—even those with inward-curving lips—crack when exposed to liquid nitrogen because of stresses developed during rapid chilling. Glasses that are uniformly thick, have flat bottoms or corners, or have thin walls and a thick base tend to crack. Pint glasses and rocks glasses are poor choices. Many stemmed glasses and most champagne flutes don’t crack with LN, but test them first. Test two or three glasses of a particular pattern. If none of your test glasses crack, buy more of those glasses and you should be fine. My experience has been that any particular glass pattern is
going to break either consistently or almost never. Quality is not an indicator of chillability.
At a pro bar, chilling glasses with LN means I don’t need a dedicated glass-chilling freezer. It may be easier at home to chill your glasses in the freezer, but at the bar, LN helps us maximize our back-of-house space.
DRY ICE
Dry ice is solidified carbon dioxide. It’s called dry because carbon dioxide doesn’t exist as a liquid at normal atmospheric pressure; it turns directly from a solid to a gas through a process called sublimation. Dry ice appears to be the friendlier cryogen— it’s easier to get, less likely to give you cryogenic burns, and, as a solid, easier to handle than liquid nitrogen. Furthermore, even though dry ice is much warmer than liquid nitrogen—a balmy −109.3°F (−78.5°C)—don’t let that warmer temperature fool you. Pound for pound, dry ice has almost twice the cooling power of liquid nitrogen, because it takes a lot of energy to turn CO2 directly from a solid into a gas (136.5 calories per gram), whereas liquid nitrogen needs only a measly 47.5 calories per gram to vaporize.
As dry ice chills, it lightly carbonates whatever liquid it is in, which is why I primarily use dry ice at events to prechill drinks that I’m about to carbonate.
The problem with dry ice: it is hard to use its cooling power effectively. Unlike liquid nitrogen, which can surround and coat solids or mix with other liquids to create a large surface area for effective rapid chilling, dry ice is a solid, so it is hard to get it to chill drinks rapidly. Drop a chunk of dry ice into a glass of liquid. Initially you get bubbling and foaming and a nice carbon dioxide fog. Pretty soon, however, the liquid calms down and your chilling rate radically slows. Look at the liquid: there’s still dry ice in there, but a layer of liquid has frozen over the dry ice, insulating it. Beat on the nugget with something to break off the frozen layer and the chilling speeds up again.
Safety rule: never use dry ice to carbonate drinks in a sealed container unless you are an engineer qualified to design pressure vessels with overpressure safety valves. Search the Internet for pictures of unsuspecting boneheads who dropped dry ice into a soda bottle and sealed it, just to have it blow up in their hands. On second thought, don’t.
An obscure but enjoyable use for dry ice is to keep large batches of drinks chilled at events. You need an immersion circulator (a device with a heater that keeps liquids at very accurate temperatures) that can be set below freezing, a large plastic tub, a bunch of cheap vodka, and some dry ice. You fill the tub with the vodka, which has a very low freezing point, set up the immersion circulator in it, and then add dry ice. A pump in the circulator will keep the vodka moving around; it stirs the bath for
you, ensuring even chilling. If the temperature drops below −16°C, the heater in the circulator will kick on and prevent overchilling.
Let’s say you are serving a high-proof drink in shot form and you want to serve it at −16°C (0°F). Put the bottles of liquor in the tub, add the cheap vodka, and put in the immersion circulator. Turn on the circulator and set it to −16°C. Now throw in some chunks of dry ice. All you need to do is look at the bath every once in a while to see if you need to throw in some more chunks of dry ice. I have served thousands of well- chilled shots and drinks at events this way. This technique can also be used to keep carbonated cocktails cold during an event.
Safety again: always make sure there is no way for someone to ingest the dry ice accidentally.