• Question: Why is it that no matter what color bubble bath you use the bubbles are always white?

    Asked by josh to Alan, Caspar, Diana, Murray, Sarah on 16 Mar 2011 in Categories: .
    • Photo: Caspar Addyman

      Caspar Addyman answered on 14 Mar 2011:

      You can make your bubbles to be a different colour but you need quite a lot of dye. (Do you remember blowing bubbles in poster paints in primary school? I do.) Bubble bath manufacturers can’t put too much dye in bubble bath because otherwise it might turn you and your bath pink or green rather than getting you clean.
      But if you don’t mind being pink or green then an experiment to try next bathtime would be to mix a whole bottle of food colouring in with your bubble bath.

      PS There is a more boring but more scientific answer to this question which is to do with how light is scattered and reflected inside bubbles.

    • Photo: Alan Winfield

      Alan Winfield answered on 16 Mar 2011:

      Hmm. Good question – I’ve really no idea. My guess is that because the walls of the soap bubbles are very thin and very transparent then you can’t actually see the colour of the soap solution when it’s frothed into bubbles.

    • Photo: Sarah Thomas

      Sarah Thomas answered on 16 Mar 2011:

      I think the bubbles aren’t white, I think they are clear.

      Have you ever noticed a sort of rainbow effect on bubbles?? This is because bubbles can act as a prism. A prism can separate out the different colours of light and that is why you can see a rainbow.

      Now here is a strange fact: when you shine a light on an object, lets say a piece of grass, contained within the light is the full spectrum of colours. All the colours are absorbed by the grass, except green. Green light is reflected back by the grass and this is why grass looks green to our eyes. The reason that some objects look white or clear is because all of the colours of light are being reflected. Things that are black, these absorb all the colours of light and that is why they look black!

    • Photo: Diana Drennan

      Diana Drennan answered on 16 Mar 2011:

      The color you see on an object is because that object is reflecting that wavelength of light and absorbing the others. So trees are green because the leaves absorb the wavelengths other than green really well, and reflect the green. So, bubble foam is white because they are reflecting all the wavelengths of light in the room (usually white). So, if you had red lights, your bubbles would be red. Interestingly, a single soap bubble reflects all the wavelengths, but because there is only one and thus limited reflectance off other bubbles, you get a rainbow effect. (at least outside, inside you might not have light-bulbs that give off all the wavelengths like the sun does)

Comments