Growing Snowflakes In A Bottle

Are you dreaming of a white Christmas? Try making your own winter wonderland. Ken Libbrecht, Caltech physicist and author of The Secret Life of a Snowflake, devised an experiment to grow a snow crystal in an old plastic bottle. Dry ice required.

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IRA FLATOW, host:

With us now is Flora Lichtman. Hi, Flora.

FLORA LICHTMAN: Hi, Ira.

FLATOW: With our digital Video Pick of the Week. Oh, this is a good one.

(Soundbite of laughter)

LICHTMAN: This week is a recipe. It's seasonal. It's a recipe for making your very own tiny winter wonderland - with the emphasis, really, belonging on the word tiny.

(Soundbite of laughter)

FLATOW: How tiny is...

LICHTMAN: Pretty tiny. It's pretty tiny.

FLATOW: Now that's...

LICHTMAN: It's not quite a white Christmas. Almost.

FLATOW: They're about snow - winter wonderland, a lot of snowy things, right?

LICHTMAN: Yes, exactly. So the experiment is from Ken Libbrecht, who's a CalTech physicist by day and a snowflake expert, probably, also by day.

FLATOW: Mm-hmm.

LICHTMAN: And he devised this experiment to grow a snow crystal in an old plastic bottle, like an old Coke bottle, or whatever.

FLATOW: Right. One of these one liter, two liter bottles, sort of.

LICHTMAN: And it's really easy. I mean, most of the stuff you have in your house, you need some string and a sponge. And the only really sort of thing you might have to go out for is the dry ice, the frozen CO2.

FLATOW: I just ran out.

(Soundbite of laughter)

LICHTMAN: Yeah, right. Not everybody has it in their cupboard.

FLATOW: But you - it's not hard to find these days.

LICHTMAN: No, apparently not. He said it's in grocery stores. I found it at, you know - in New York, of course, there's an ice cube store. There's a store for everything here.

FLATOW: Store for just ice? Another story, but - stores just for ice cubes?

LICHTMAN: Yeah, it is another story.

(Soundbite of laughter)

LICHTMAN: So you put them all together. Basically, you emerge the plastic bottle in this cup of dry ice or a bucket of dry ice, and you have a wet sponge on top. And what you're doing is you're creating, inside the bottle, all this humid air. And you have a really big temperature gradient, because the bottom of the bottle is very cold because it's next to the dry ice, which is minus 60 degrees. And at the top, it's warm because it's in your house, presumably.

FLATOW: Mm-hmm.

LICHTMAN: And what happens is the vapor travels around - these vapor molecules of water travel around, and you've got a string hanging down from the bottle. And when they hit the string in the cold air, the air is super saturated, and they condense onto the string and they grow a crystal right before your eyes.

FLATOW: Wow. And you actually - you show this on your video, on our SCIENCE FRIDAY Video Pick of the Week. Go to our website at sciencefriday.com. It's the video on the top left. And you have a sort of time lapse of watching this crystal grow.

LICHTMAN: Yeah. Aleszu Bajak - a producer of SCIENCE FRIDAY - and I did this experiment about 10 times, and my...

FLATOW: Did it take 10 times?

LICHTMAN: It took a few times.

FLATOW: So be patient.

LICHTMAN: Be patient. And actually, the best version was definitely when I went to go make dinner in between starting it and stopping it. You need to be patient. It took an hour to really grow something nice. But once - you know, when I came back, I was amazed. Really, it was beautiful. And Ken Libbrecht says that, actually, different crystals will grow - different types of crystals will grow on different parts of the string because of the temperature differences. And this is sort of the big mystery that he's interested in: Why do different temperatures produce different shapes of snowflakes, essentially?

FLATOW: Right. And we know no two are the same, or...

LICHTMAN: I - we'll let him take him - let him take that up. I'm not sure that's true.

FLATOW: But that's interesting. And if you go to our - this is a project you can do at home.

LICHTMAN: It's very easy.

FLATOW: It's safe enough that if you get the gloves and the, you know, the goggles - playing with dry ice. Don't forget that.

LICHTMAN: Yeah, use your mittens.

FLATOW: And you can, you know, sit and watch this around, you know, in the evening, put it together in one evening, right?

LICHTMAN: Yup, absolutely. And let us know if you do, what you come up with, if you get any, you know, dendrite crystals or...

FLATOW: Yeah. Send us a video of your - or a snapshot...

LICHTMAN: Or send pictures.

FLATOW: ...some pictures of your snowflakes that you're growing. Thank you.

LICHTMAN: Thanks.

FLATOW: And that's Flora Lichtman and our Video Pick of the Week up there on our website at sciencefriday.com. You can do this one at home.

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