Why do we stick to ice?

22 March 2009

Question

Why is ice sticky, especially when you touch it with wet hands or with your tongue?

Answer

Chris - I've had a nasty experience because I used to work in a lab where we had lots of -70 freezers. We used to develop various gels and things in those -70 freezers. If you weren't careful and didn't put some gloves on when you went into the freezer and grabbed your developer out then your skin could freeze onto the rack. When you removed your fingers and let go then it left a lovely fingerprint on the thing. That quite literally was a fingerprint because it left the surface layers of skin from your finger. The reason ice is sticky is for that very reason. Ice itself is so cold if you touch it with skin because your body secretes tiny amounts of liquid, sweat, which is a salty fluid onto your skin surface it actually makes your skin stickier. This is why we have it. It's for grip. If you then touch that onto a very cold ice surface the ice then re-freezes the liquid on your finger. Because that liquid is a fluid and it has got into all the nooks and crannies on your finger it then freezes solid and will form a very tight bond between your finger and the frozen surface, the ice. You get stuck to the surface. If it's an ice cube - if it's okay because there's enough heat flowing through your fingers (usually to re-melt that transient freezing) then you can detach yourself. In the case of a -70 freezer or even colder, people in the Antarctic have to be very careful about this kind of thing. It doesn't warm up and you can end up permanently frozen to the surface or you can do quite a bad injury. That's why ice is sticky. You get literally frozen to the spot.

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