51 replies to this topic

[davidkeay]

In terms of pure novelty factor, frozen honey was very interesting. I froze about a tbsp of it by dropping it into about 1/4 cup of LN, and then broke it up with a fork (and hammer) once it was frozen solid. I ended up with crystals about 1/2 the diameter of a pea that looked like glass. When you bit into one, it would make an amazingly loud squeaky-crunch. It's a little hard to describe, but it shatters in your mouth in an interesting way (right before it melts into honey, of course). It reminds me a little of the way that cornstarch suspended in water behaves both like a viscous liquid and a solid at the same time.

[LoftyNotions]

I just did some rough calculations of what amount of air 2.5 liters of liquid nitrogen would displace. At 700 X expansion, it would displace 61.8 cubic feet of air. Assuming you're in a sealed room measuring 10 feet by 10 feet by 8 feet, the room holds 800 cubic feet of air ignoring cabinets, people, etc.

That works out to replacing approximately 7.7 percent of the room air. With air being about 21 percent oxygen that would bring the room oxygen level down to around 16 percent.

17% O2 level causes anoxia
10-14% O2 level causes dizziness
6-8% O2 level causes collapse
Less than 3% O2 causes death within 45 seconds

Of course, a spill in a smaller enclosed area such as a car would have much more dire consequences than a spill in an open area as would a spill of a much larger quantity.

As far as protective clothing goes, definitely wear at least safety glasses or goggles if not a full face shield. As mentioned above, absorbent clothing such as oven mitts can be more dangerous than bare skin. We wore Welder's gloves when doing liquid nitrogen and liquid helium transfills. The silicone gloves would work very well in this application.

[dcarch]

"---The silicone gloves would work very well in this application. "


Can we verify that?

Silicone rubber is about from -55°C to +300°C while still maintaining its useful properties. At LN temperature would silicone become very brittle?

dcarch

[LoftyNotions]

"---The silicone gloves would work very well in this application. "


Can we verify that?

Silicone rubber is about from -55°C to +300°C while still maintaining its useful properties. At LN temperature would silicone become very brittle?

dcarch

I wasn't thinking in terms of long term immersion in liquid nitrogen. I'd use them more for short exposure and to protect myself from exposure to objects chilled by the nitrogen. I watched an old Iron Chef episode last night where Homaro Cantu was submerging objects with his bare hands.His hands were actually in the liquid nitrogen for brief periods. I wouldn't personally long term immerse either my bare hands or hands covered with any kind of glove. I guess the easy way to answer your question would be to immerse a glove (sans hand)and see what happens.

One other piece of advice regarding gloves/mitts... they should be loose enough to shake off if you need to.

Best bet: Buy a pair of welder's gloves. Worst bet: Use regular cloth oven gloves. Better than nothing: Silicone mitts.

By the way, Cantu didn't wear any protection, so I wouldn't use him as a good safety example.

Hopefully this clears up my thinking at least a little.

Thanks,

Larry

[tomdarch]

"---The silicone gloves would work very well in this application. "

Can we verify that?

Silicone rubber is about from -55°C to +300°C while still maintaining its useful properties. At LN temperature would silicone become very brittle?

dcarch

I haven't re-read the Cooking Issues guide to LN2 in a while, but I think I remember comments about selecting protective gear in part on "what happens if LN2 pours into the cuff." The downside to silicone mitts is that if some quantity gets into the glove, it will be trapped against your skin. This might be even more of an issue with welders' gloves, which have an even wider, shorter "cuff" or "gauntlet." The same issue stands for selecting shoes...

That said, I suspect that using a small quantity of LN2 at home for "novelty" purposes is a lot different than using it day in and day out at a restaurant. At home, you're approaching it with wide-eyed caution and a bit of "beginners mind," where at work, you may get lax.

Another use I've for LN2 is "herb dust" - freezing fresh herbs, then crushing them into a fine powder, which thaws back into a dust of fresh herb flavor. I also recall seeing Cantu and the MOTO guys making "juice balls" working with LN2 bare handed. They put a few tablespoons of juice (beet, in this case) into a normal balloon, filled it with a bit more air, and tied it shut. They then rolled the juice/air filled balloon around on the surface of the LN2. The juice froze on the inside surface of the balloon, freezing into a hollow sphere. They cut the balloon away, leaving the sphere to be plated.

[LoftyNotions]

I haven't re-read the Cooking Issues guide to LN2 in a while, but I think I remember comments about selecting protective gear in part on "what happens if LN2 pours into the cuff." The downside to silicone mitts is that if some quantity gets into the glove, it will be trapped against your skin. This might be even more of an issue with welders' gloves, which have an even wider, shorter "cuff" or "gauntlet." The same issue stands for selecting shoes...

That's part of the reason for only wearing a glove/mitt that can be shaken off. Welding gloves were standard wear for us while handling cryogens.

As far as thermal hazard is concerned, we work with oil heated to 375 F and don't think too much about it. Given a choice of quickly dunking my hand in LN2 or hot oil, I'd take the LN2 any day.

It's a tool that should be understood and respected, but not feared.

[Hayley Casarotto]

I use LN2 at work (science, not food-related). I tend to wear two layers of gloves - rubber on the outside for lack of permeability, thick cloth on the inside for insulation.

Like many have noted, if you do the right thing and treat it with respect, then it's nothing to be afraid of. Having said that, I'd like to emphasize this - please please please please wear safety goggles. If it gets on your skin, the residual heat your skin produces will stop it from burning you right away, and you can usually brush it off without any problems. If it gets in your nice wet eye, your eye will freeze. Immediately. So please, if you do nothing else, wear proper eye protection. I've seen the pictures so you don't have to.
Kudos to everybody who has spoken about air displacement already. We transport it on the back tray of a ute (I think that's a pickup to Americans?) rather than in the cabin.

One more thing - submerge your tools (ladles, tongs etc) into it slowly, rather than dunking them on in, to avoid any violent boiling over. Other than that, have fun!

[blue_dolphin]

Oven gloves and safety glasses.

...As far as protective clothing goes, definitely wear at least safety glasses or goggles if not a full face shield....

...I'd like to emphasize this - please please please please wear safety goggles....

Another vote for eye protection. You do not want this stuff, even a droplet, in your eyes! It's way more prone to violent boiling than hot oil so extra caution is really appropriate.

I've only used LN2 at work, in a lab. The only food related "experiment" I remember was eating LN2 dipped graham crackers and blowing smoke rings.

[davidkeay]

One more thing - submerge your tools (ladles, tongs etc) into it slowly, rather than dunking them on in, to avoid any violent boiling over. Other than that, have fun!

This is a good point that I forget about when I tell people how to handle the stuff. Since I store mine in an airpot, I use the built in metal straw and pump mechanism to dispense it. When I go to actually insert the straw and pump into the LN, I have to go slowly. If I insert it too fast, the boiling action will cause LN to actually spray out the end of the straw... dramatic, but definitely not something you want happening by surprise.

[LoftyNotions]

One more safety precaution I don't remember seeing here is to remove all rings, bracelets and metal watches before handling LN2.

On another note, for those who feel that welding gloves or silicone mitts are not sufficient protection, here is another (more expensive) option:

http://www.2spi.com/...cryo-gloves.php

[avaserfi]

I just found a local welding supply place that sells liquid nitrogen by the pound. I am really excited about starting to work with the substance, but won’t be able to get a dewar since they are too expensive. I called the welding supply and asked for suggestions. They said they have people come in with plastic coolers (although they did point out that the interior plastic does crack), styrofoam coolers and dewars.

Given my situation and the fact that I won’t need a lot of liquid nitrogen at a time (cooking for 2) does anyone have any suggestions? It seems a small plastic cooler would be the least expensive option, but might not be safe? Alternatively I was thinking about getting a 1-2 liter thermal carafe and making it (or making sure) it is vented.

Would 2 liters be enough to get some experience with the technique or would it sublimate too quickly from a thermal carafe for practical use?

I don't have a truck for transport, so at best I can keep it in the trunk on the drive home. Does

[gfweb]

I think there'd be too much sloshing with a cooler in a trunk.

I'd buy a big thermous and drill a small hole completely through the cap to vent it. This is critical. LN2 will go off like a bomb if kept sealed. The only shortcoming of using a drilled thermous is that it loses a bit more N2 than a Dewar since the internal pressure is a bit lower.

If you did use a styrofoam cooler perhaps some baffles could be put in to keep the sloshing down.

Whatever you end up using, venting is critical.

[bmdaniel]

You could probably use the vacuum insulated coffee dispenser Dave Arnold recommends (or two) - he says it loses 50% of its volume in 24 hours, so it will probably work if you just want to use it for a day or two.

http://www.cookingis...itrogen-primer/ - scroll down about a quarter of the way

[avaserfi]

I think there'd be too much sloshing with a cooler in a trunk.

I'd buy a big thermous and drill a small hole completely through the cap to vent it. This is critical. LN2 will go off like a bomb if kept sealed. The only shortcoming of using a drilled thermous is that it loses a bit more N2 than a Dewar since the internal pressure is a bit lower.

If you did use a styrofoam cooler perhaps some baffles could be put in to keep the sloshing down.

Whatever you end up using, venting is critical.

I will most definitely allow the vessel to vent. In the Cooking Issues primer they recommend against keeping the LN2 in the passanger portion of a car. The trunk is the best I can do, but I can drive carefully and keep the vessel held in place in a larger box to prevent/minimize sloshing.

You could probably use the vacuum insulated coffee dispenser Dave Arnold recommends (or two) - he says it loses 50% of its volume in 24 hours, so it will probably work if you just want to use it for a day or two.

http://www.cookingissues.com/primers/liquid-nitrogen-primer/ - scroll down about a quarter of the way

Yeah I saw the dispenser he recommended, but don't know enough about them to know what to order. Do you have any idea on the type they use?

[bmdaniel]

Yeah I saw the dispenser he recommended, but don't know enough about them to know what to order. Do you have any idea on the type they use?

I would just run to a restaurant supply - I am sure they will have them and you can make sure they are vented before you buy.

Otherwise, you can get something like this on Amazon for $28, but I can't be sure it vents naturally(probably does, but you may have to return if not)

[Judy Wilson]

One of our culinary research assistants just blogged about his experience with liquid nitrogen, which he's been cooking with for more than five years. So far, only one bad incident to speak of!

But basically he says a lot of what has been said here: wear gloves, don't use it in closed, unventilated areas, wear shoes that aren't made of fabric (in case some drips on your foot), etc.

[paulraphael]

I just did some rough calculations of what amount of air 2.5 liters of liquid nitrogen would displace. At 700 X expansion, it would displace 61.8 cubic feet of air. Assuming you're in a sealed room measuring 10 feet by 10 feet by 8 feet, the room holds 800 cubic feet of air ignoring cabinets, people, etc.

The trouble is that LN2 and air won't mix evenly. The LN2 will generally dsplace most of the air in the lower half of the room. The other trouble is that unlike C02, it doesn't make people ghasp for breath. People just get sleepy and lie down, often dramatically.

I think the most important precautions, mostly already mentioned are:

1) unsealed (and unsealable) container
2) safety goggles. a drop splashed in your eye can be very, very bad
3) ventilation
4) no clothes that could accumulate LN2 and hold it next to your skin (boots that are open at the top, etc...)

If you spill the stuff on open skin it just rolls and boils off. But if it ends up inside a glove or a shoe, with nowhere to go, you can get instant and extreme frotbite. I don't think full lab saftey gear is necessary ... my scientist friends who work in actual labs don't bother with it ... but some basic precautions like pants cuffs pulled down over your shoes, long, unabsorbent gloves (if you're wearing gloves at all), etc., are smart precautions.

[Skywater]

My local suppliers will only sell you liquid nitrogen if have a dewar or rent one of theirs.

[mkayahara]

My local suppliers will only sell you liquid nitrogen if have a dewar or rent one of theirs.

As they should. Transporting liquid nitrogen in any other container is just asking for trouble.

[Broken English]

How much is it on average?

Also, Heston Blumenthal was on The Jonathan Ross Show and he was dsipping his bare hands into it and flicking it at Ross, which made for quite an amusing scene. Extrapolating from this, I'd assume that it's okay to touch, if only very briefly.

[Dexter]

I know this is super late, but a professor of mine in college called it the Leidenfrost Effect - basically the same thing that makes droplets of water skitter across a hot surface without just sitting down and boiling away. A layer of rapidly forming vapor insulates the warm and cold bodies, and keeping them slightly apart. He demonstrated it by holding his hand out, fingers together, like he was sticking his hand out to shake someone elses', the poured LN2 over the top. Did it to a couple of students too. Made the point stand out in my head, even 20 something years later.

[Dexter]

Actually, now that I've gravedug this particular thread, I might as well drop this question in here as well:

Does anyone know of a good, smallish (2 person household, guests on occasion) Dewar they'd recommend, and a place that sells them? Getting it filled up isn't as much of a problem, but I'm hesitant to going the Ebay route for this kind of equipment.