Independence Day. And Nuclear Ice Cream

 "God has a special providence for fools, drunkards, and the United States of America." - Otto Von Bismarck, German Chancellor, 1871-1890

Where is a magnificent diplomat like Bismarck when the world really needs one?

Happy Independence Day.

Story time again.

I've been thinking lately about getting a Dewar flask - many working-class people already have one of these things.  Everyone that I know used to have a tiny Dewar flask.  I still have mine!  These are usually  called Thermos bottles.  The Dewar that I once filled with coffee every morning was a Stanley brand, rather than a 'Thermos' brand, but the process was identical - it was still a glass vacuum flask.  The commute is not quite so long anymore, so I can get by without one.  It's currently sitting in a storage cabinet.

What's inside a Thermos flask?  A double-walled glass container, with the air pumped out between the walls, and a reflective coating applied inside.  Removing the air reduces heat loss due to convection and conduction, while the reflective coating reduces heat loss due to radiation.  

Yeah, you remember this point of view, don't you?

Modern Yeti cups accomplish the same thing, but with stainless steel.  This is not as effective, but its much less delicate and less expensive to manufacture.  Not sure how the copper plating helps, but I'm sure there's a good reason for it.

Vacuum flasks are handy for other things than keeping your coffee warm though.  They are the standard storage container for holding liquid Nitrogen.

The Dewar flask that I'm interested in is a bit smaller than the above bulk storage container, but larger than a coffee thermos.  This one is for freezing and transporting bull or stallion er... DNA.  It even has long-handled sample holders to drop the ...DNA samples down into the liquid Nitrogen and retrieve it without freezing your fingers.

I may decide to buy this 6 liter capacity dewar flask - it's not cheap, but it's also not that expensive.  The sample containers will go in the trash, because I don't need to transport ... DNA to a mare.   I just need to store a modest quantity of liquid Nitrogen for a modest amount of time.  Why?  Because it's been a long time since I've made "Nuclear Ice Cream". 

There's nothing radioactive about Nuclear Ice Cream - it's just a nick-name for making ice cream really really fast, by cooling the liquid cream mixture with cryogenic liquid Nitrogen.  When I worked at General Atomics, I had access to liquid Nitrogen and a dewar flask whenever I wanted.  I made Nuclear Ice Cream in my apartment all the time, to the great delight of my friends.

The last time I had access to liquid Nitrogen was about 20 years ago.  I managed to make Nuclear Ice Cream, even though I didn't have a dewar flask - because it wasn't necessary to transport the liquid Nitrogen - just a few hundred feet.  I just filled a plastic bucket and quickly used the Nitrogen before it could evaporate.  Just so you know, it's important to wear proper personal protective equipment when handling cryogenic liquids - goggles, face shield, rubber apron, insulated gloves, and long sleeves.  Safety first!

Below:  Nobody was delighted this time around :(

Liquid Nitrogen really isn't that dangerous.  It's cold, but it takes a fair bit of contact time for it to actually freeze skin, even though it's -320F (-196C).  It immediately evaporates when it touches something warm, so it is reasonably safe to handle, assuming you have good ventilation.

It takes 2-3 minutes to make Ice Cream using a bucket of liquid Nitrogen.  Compare that to 30-45 minutes for hand-made ice cream using ice and salt.  This was always a chore that adults would stick us kids with at picnics.  I still resent that.  Your arms would fall off before ice cream would be ready, and it got harder to crank as the ice cream froze up.

 

The only real down-side to making cryogenic ice cream is that it tends to be a lot more crunchy and crystalline than ice cream that has been cooled down more slowly.  Even so, it still tastes great, and your arms are still intact.  Also there are better visual effects, and you can toss a spoonful of nitrogen on the floor and watch the droplets skitter around.

I was reminded of Nuclear Ice Cream when I made the earlier post about the Hot Cell Mess.  The head physicist of the Hot Cell at General Atomics is the one who taught me how to make ice cream really really fast, and to have fun while doing it.  

I have to say that the job at GA was incredibly rewarding from an intellectual reference.  Too bad I was slowly going broke, due to San Diego's incredibly low wages and high cost of living.  It really was a cool place to work at the time.

Below:  The General Atomics campus - with atomic age architecture.  I never used the pool or tennis courts.  That's the famous Torrey Pines Golf Course at the top left.