Have you ever spilled water in your lap right before having to present at a big meeting? Or perhaps you’ve felt your underarms start to sweat in the middle of a date that seems to be going well? In both of these situations, and plenty of other ones, you’ve likely noticed that fabrics and cloth tend to darken in color when they get wet! It would certainly be nice if moisture didn’t change the color of our clothes so noticeably, but it’s an unavoidable part of life. The question is, why do things appear darker when they get wet?
How We Perceive Color
Before we can understand the nuances of material colors changing based on the presence of moisture, we should take a quick refresher on how colors are perceived in the first place. When light from the sun streams into our atmosphere and strikes a field of grass, we perceive that grass to be green because the light energy is only partially absorbed.
The grass will absorb wavelengths of light in the blue, red, yellow and orange range of the electromagnetic spectrum, but it will reflect green light wavelengths (560-520nm). Thus, the light that bounces back from the grass is taken in by our eyes, where it hits the cone cells in our retina, and is translated visually to green grass!
This is the case with everything we look at; the diverse range of colors that we perceive in the world, from the color of a tree to the shades of our clothes and the hues of products we buy, is completely dependent on how light is either absorbed or reflected by those objects.
Additionally, the texture and composition of the material can affect how we see color. For example, an article of clothing is composed of many layers of tiny fibers, which provides a lot of surface area for light to be reflected.
Even though a material may be partially transparent, the multiple layers and countless individual fibers reflect the color back at the observer. A white t-shirt, for example, is composed of fibers that are mostly transparent, but in such large numbers and concentrations, they generate a vibrant white color. The interaction of all that fabric, light and air creates the appearance of a solid color to an observer’s eyes.
Also, fabric may feel smooth, but all those fibers make for quite a rough surface on a microscopic level. Rough surfaces tend to look brighter than smooth surfaces, because the incident light has more angles to bounce off, generating more reflection and creating a brighter appearance. Smooth surfaces, like metal or glass, tend to reflect light in a single direction based on the incident light angle.