How can we know why things turn darker when they wet?

[princezephyr]

I have searched for the experiment (like how to do it) related to how we can know why things turn darker when they wet and found nothing. All I found is the conclusion and it's not what I'm searching for. If i just pour some water on a cloth and sum up the experiment it doesn't seem right... Anyone please kindly helps me?

 

[mfb]

Do you look for an explanation, or for a way to conduct an experiment?

If i just pour some water on a cloth and sum up the experiment it doesn't seem right

Why not? Make photos to analyze them, test different materials (not all will show the same effect).

 

[CWatters]

One paper proposes that diffuse reflection from the material is internally reflected off the surface of the water (so less is available to reach your eys). If that's the cause then perhaps increasing the depth of the water or using a liquid with a different critical angle would make a difference to the brightness?