SEx Education: Ice Spy

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Science Explained

Ice Spy

If the latest predictions on climate change are accurate, then there may not be many icebergs around in the future, so let's hope the SExperts can answer Yvonne's question before it's too late...

Water is often represeted by blue colours in images, and if asked, most people say that ice is either clear or white. How come when looking at snowfields and glaciers the ice usually appears blue coloured?

Yvonne herself suggested one possible reason: 'Is this something to do with impurities?', and Mr. Dreadful agreed that they might play a part:

Water appears blue/green when in sufficient quantities due to copper oxides and similar impurities

Indeed it does, as anyone who has handled solutions of copper sulphate1, or the poor people on a housing estate in Sheffield, whose badly-installed copper pipes have meant that their tap-water is a subtle shade of blue, can attest.

But what about pure water and ice? Are they also blue? Surely water is clear and ice is white, right..?

White ice is due to the ice having lots of air bubbles and impurities in it.

So pure ice is clear, like pure water, yes..?

The answer to the question depends entirely on how much of the substance you're talking about. A glass of water = no color. A glass of ice = the same. It's completely transparent, reflects no light, and therefore has no color.

A large mass of water = blue. A large mass of ice = the same. Once you get enough of it together, it starts absorbing light from the red end of the spectrum, reflecting blue.

Blatherskite the Mugwump

So ice and water are blue after all. To prove it, Thatprat provided a link to a picture of a blue iceberg. Even more convicing, Aurora pointed us at a picture from the Kamiokande Neutrino Detector, which is filled with 50,000 tons of pure water that are very definitely blue.


This article was based on a conversation at the SEx forum — where science is explained.

Why not pop over with your own questions? The pick of the bunch will feature in The Post's next

SEx Education Archive

Danny B.


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1Or 'sulfate', as I believe we now have to call it.

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