Why does water sometimes appear BLUE and sometimes WHITE?

Question: Why does water sometimes appear BLUE and sometimes WHITE?
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- Royal Society of Chemistry: Find out more on:
  
  blue
  
  water
  
  white
Asked by fierylittle1 to Kate, Kieren, Nicola, Rowena, Roy on 13 Mar 2014.
- Kieren Bradley answered on 13 Mar 2014:
  
  Water is actually blue, as in it absorbs colours other than blue so appears blue to us. But it doesn’t really do it very well so usually you don’t see that it is blue. In fact when you see a blue sea the majority of the reason is that it is reflecting the sky rather than actually being blue itself.
  
  When you say white water, I assume you mean when it is churned up like it river rapids, waves or even clouds. When it gets churned up it forms very water droplets which are very good at reflecting all the light which makes it go white. You get the same sort of reflections when you see soap bubbles, hence why they are also white.
- Kate Nicholson answered on 14 Mar 2014:
  
  Water is blue, although as Kieran points out so well, not a very deep colour of blue because it doesn’t really absorb that much light. The white colour is usually when it is foamy, lots of air is trapped as bubbles inside it which will scatter light a lot better, as will the fine droplets (just look at the clouds)
- Rowena Fletcher-Wood answered on 14 Mar 2014:
  
  When water gets frothed up it forms loads and loads of little droplets which go in all different directions at the same time. Light is scattered like craxy when this happens because everywhere it goes it bounces off another droplet going a different way and crisscrosses erratically. When systems crisscross in an ordered way you get patterns of light and dark from overlaps which show the crystal pattern. This is how x-ray diffraction works and how I showed the diamond in my engagement ring to be a diamond. But water is liquid and it doesn’t show a crystal pattern (plus the wavelength of light is quite big) so we just see a blurrrrr of light and that’s why you can’t see the blue.
- Nicola Rogers answered on 14 Mar 2014:
  
  This is very similar to the idea of why a pane of glass looks colourless, but if it was ground up into small particles it would look like salt – and hence white. Similarly, the small grains of glass will scatter light at every interface – i.e. every time light moves between air and glass, and hence it scatters a lot and most of the light is scattered back to your eyes, rather than passing straight through the glass

Question: Why does water sometimes appear BLUE and sometimes WHITE?

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