• Question: Why do clothes turn darker when they are wet?

    Asked by tosty55 to Aggelos, Andrew, Eileen, Naomi, Shane on 14 Nov 2012.
    • Photo: Andrew Jackson

      Andrew Jackson answered on 14 Nov 2012:

      wow, great question I dont know, but i guess what could be happening is that the presence of water means that it absorbs more light that lands on it, so reflecting less light back to our eye and making it appear darker while pretty much the same color. Thats a guess though 😉

    • Photo: Eileen Diskin

      Eileen Diskin answered on 14 Nov 2012:

      Yep, I think that Andrew’s got it! The waters absorbing some of the light, so less of its reflected back…making it less bright!

      Some scientists are working on making really cool clothing that repells water…one of the kinds of water-repellent clothing can be soaked in water for TWO MONTHS and still come out totally dry. How cool is that?!

    • Photo: Aggelos Zacharopoulos

      Aggelos Zacharopoulos answered on 15 Nov 2012:

      when a cloth gets wet it reduces the amount of light that is reflected from it. So they look darker to us. This is because the water molecules on the cloth due to their refractive index will absorb more light compared to the dry cloth molecules.

    • Photo: Shane Bergin

      Shane Bergin answered on 16 Nov 2012:

      This has been driving me mad! it’s a brilliant question. I have to disagree with my colleague about the water absorbing light and making it appear darker. Water is transparent in the visible part of the spectrum so it’s a bit more complicated… I ask LOTS of the other professors and here’s an answer i believe (note a photon is a ‘bit’ of light)

      A wet cloth looks darker because less light is reflected from a wet cloth. Any cloth is woven from a yarn or fibre. That fibre is in turn made of smaller micro-fibres. Light comes from the room lights, or from the Sun, and lands on the cloth. Some of the photons of light are absorbed, but some are reflected and land on your retina – and that gives you the sensation of seeing the cloth as having a certain level of brightness. But when the cloth gets wet, the water fills in the gaps between each individual strand of fibre, and also between each individual micro-fibre. When light falls on the wet cloth, some of it is now more likely to enter the water, and be bent away from your eyes. So some of the light that would have previously been reflected off the cloth back to your eyes, is now bent away.

      Fewer photons of light get back to your eyeball, and so the wet cloth “appears” darker than the dry cloth. But as the water gradually evaporates, more and more light is reflected back to your eyeball, and you see the brighter colour of the fabric again.