Behold the smooth, sweet powers of liquid N (Liquid nitrogen ice cream! Yum!)

Popular Science ^ | July 2003 | Theodore Gray

[mhking]

Liquid nitrogen is cold. Very cold. So cold that if a drop falls on your hand, it feels like fire. So cold that it can turn a fresh flower into a thousand shards of broken glass. So cold that it can make half a gallon of ice cream in 30 seconds flat.

I first heard about liquid nitrogen ice cream from my friend Tryggvi, an Icelandic chemist working in the Midwest (these things happen). He suggested we make it for dessert at a dinner party I was planning. Yes, he said, he had a recipe, something he'd seen in Chemical and Engineering News.

Now, right off the bat you have to worry about a recipe found in Chemical and Engineering News, the principal trade publication for the sort of people who build oil refineries, shampoo factories and large-scale plants for the fractional distillation of liquefied air (which is where liquid nitrogen comes from). But for the party I was planning, it was perfect: The well-known author Oliver Sacks was coming to visit with my collection of chemical elements; I needed some after-dinner entertainment.

My first concern was whether we would survive the ice cream. That and, if it didn't kill the cook, whether it would be any good. I had visions of hard, crusty stuff that caused frostbite of the throat. It turned out nothing could be further from the truth.

We mixed up a standard ice cream recipe calling for two quarts of cream, sugar, eggs, vanilla and flavoring. (Just about any ice cream recipe and flavor will work.) Then, working in a well-ventilated area (lest the nitrogen displace oxygen from the air) and with due regard for the ability of liquid nitrogen to freeze body parts solid, we gently folded about two liters of nitrogen syrup directly into the cream, much as you would fold in egg whites.

The result, literally 30 seconds later, was a half-gallon of the best ice cream I'd ever tasted. The secret is in the rapid freezing. When cream is frozen by liquid nitrogen at –196°C, the ice crystals that give bad ice cream its grainy texture have no chance to form. Instead you get microcrystalline ice cream that is supremely smooth, creamy and light in texture. Martha Stewart, eat your heart out.

The kids were amused by the clouds of water vapor, though being kids they didn't find anything out of the ordinary in the procedure. They probably think everyone makes ice cream this way. Boy, will they be in for a shock the first time they see it done the old-fashioned way at camp: You want me to do what for a half hour?

A word of caution: Liquid nitrogen can be dangerous in careless hands. Tryggvi and I are both trained chemists, and he actually knows what he's doing. Don't try anything like this unless you do too.

[MHGinTN]

Have you tried a Berz-0-matic for lighting the charcoal and getting it quickly to 'cooking white'?

[Jubal Harshaw]

Actually, it's because N2 contains no oxygen. Room air contains ~21% O2. The O2 combines with the rubber in the tires, forming a solid oxidized rubber dust. This process:

(1) reduces the amount of gas available to keep the tire full (since the O2 is no longer a gas)

(2) causes the tire to fail.

N2 doesn't react with rubber (or with anything else, for that matter, under the conditions found inside a tire), so it stays in gas form, and the tires last longer.

Water vapor is also theoretically bad for the inside of tires, since it allows microorganisms to grow in the tire, but vulcanized rubber is apparently toxic enough to the little buggers that this is generally not a problem.

[HiTech RedNeck]

I've never heard of tires being found full of oxidized rubber powder. It would seem to me that if this truly is a problem, some kind of coating on the inside of the tire would work just as well.

[Jubal Harshaw]

Whoops. I forgot about the effect of water + O2 on the metal parts of the tire. Water + O2 rusts the steel belts and valve parts of the tire. Yet another way in which N2 (no H2O or O2) improves the life of the tire.

[JerseyHighlander]

Do either of you have the Purdue University professor's LOX barbeque explosion video? I've been looking for it since it was first posted on FR, just days before the university made the professor remove the video from his website.

[Jubal Harshaw]

(1) The oxidized rubber does not fall into the inside of the tire; it's generally still in the tire matrix, but without the structural properties that helped keep the tire together before the rubber was oxidized. Perhaps I should not have used the word "dust" in this context; I was simply trying to provide a visualization of how the rubber fails after being oxidized. Your question illuminated the fact that I did a bad job. So, please forget the word "dust;" try "non-structurally stable rubber" instead.

(2) Tires do have inner liners, as well as antioxidants within the tires material itself. These are both subject to oxidation, and eventually wear out.

[mvpel]

You mean Dippin' Dots?

[Old Professer]

LOX? You mean LOX? Not lox?

Damn, no wonder I have such a messy, oily, stinky grill!

Now, what do I do with all these bagels.

[Old Professer]

When the history of the world is finally written it will be revealed that it was oxygen that reduced it all to dust.

[nightdriver]

"You mean Dippin' Dots?"

Most likely the same process, however what I saw twenty years before this guy patented "Dots" was a lot finer grained.

Back in the sixties they were looking for markets for liquid nitrogen as the demand for it is not nearly as great as it is for oxygen and they produce almost four times as much of it to get oxygen out of atmospheric air.

This ice cream process was just one of the suggestions.

[fightinJAG]

Very cool post, king! Thanks.

[Tijeras_Slim]

A themos bottle is a dewar and would work, you just don't want to close it tightly, as LN2 expands by a factor of almost 900 when it changes to gas. I get 230 liters for about $180.

[sauropod]

Pretty cool story!

[gitmo]

Too salty.

[Freedom4US]

Another use for nitrogen that's well known around aircraft maintenance circles is it's use in vehicle tires instead of compressed air. It stops most all slow leaks.

I never heard anything about slow leaks. That would get repaired, not "stop-a-flat" anyway. The nitrogen is inert, will not react with the rubber as oxygen will. It's also dry nitrogen, so moisture will not accumulate as in automobile tires.

[Neologic]

Apparently, the temperature differential between your body and the liquid nitrogen is so great that the radiant heat from you hand causes the stuff to instantly boil and forms an insulating layer of gas between them.

You are referring to the Leidenfrost effect. It's really quite fascinating and you can do more than hold a ball of liquid nitrogen in your hands. It's even possible to dip your hand into molten lead or to gargle liquid nitrogen, if you know what you are doing. See this page for some interesting discussion and cool photos of the above.

[Alex Murphy]

I wonder if these guys use lox as a barbecue starter?

I've seen it done. Open bucket of the stuff, attached to a ten-foot pole, poured over a single lit coal.

Kids, do not try this at home.

[Drango]

It's even possible to dip your hand into molten lead or to gargle liquid nitrogen,

Just wondering out loud...how was the first idiot to try this?

[Blood of Tyrants]

And where does one get a quart of liquid nitrogen to play with?

[Blood of Tyrants]

Partially correct. Crystal formation and freezing temperatures and such are technically part of the studies in chemistry.