Why are things shiny (or shinier) when wet?

It is quite often that we observe things appear shinier when they are wet. Whether it may be while washing the car or rain falling down on metal surfaces, things look more reflective and shinier than usual. You might have wondered why is that so? And the answer is quite simple.

When a surface becomes wet, it has a very thin layer of coating on top of it. As is the case, now you are not looking directly at the surface rather looking through the surface of the water. Basically, that very thin layer of water is both smooth and flat. This is one of the reasons that the surface looks shinier. If the surface is flat without any holes, chips, and gouges, the water is able to reflect evenly as well. This reflection of light is exactly what we see as being ‘shiny.’ 

The same logic is followed when you polish and wax the car. The purpose is to level out the surface by clearing it of any microscopic impurities. Otherwise, if you were to apply both polish and wax without preparing the base, neither would the wax stick, nor will the shine pop out. You will be clearly able to see the impurities existing on the surface. Therefore, when the surface is level and has been properly buffed out, the light will reflect evenly on the entire body. 

Moreover, detailers across the globe rely on high-tech machinery and products to provide ultimate detailing services to their customers. Not only that, but the shine also has to stand out for as long as it can and should protect the original paint of the vehicle as well. Therefore, manufacturers of detailing products come up with products like polish, wax, sealant, and coatings to keep the car in showroom condition. Before ceramic or glass coating the car, it is made sure that the surface is not uneven or contains bumps. If that is the case, then the light will be reflected in different directions. Keeping in mind, the detailing specialists begin by using a clay bar and then gradually proceed towards coating the car. All while making sure that every inch is even in terms of shine.

So now, if you were to wash the car, it will look much more glossy. With water on its surface, the reflection of light will be equal, resulting in an equal shine. 

Furthermore, when you look at anything, what you’re really seeing is light bouncing off of that object and then traveling to your eyes. When light strikes a surface, it will reflect at the same angle that it struck the surface at, 100% of the time, according to what is known in optics as “the law of reflection”.

Now, look at the nearest flat surface. It looks perfectly flat, but it isn’t. 

If you zoom in, to a molecular level, you’d be able to see that the surface is really, really bumpy. Imagine playing ping-pong on a table that wasn’t flat but was instead covered in bumps and deformities. When the ball hits the side of a bump it wouldn’t reflect and keep moving to the other side of the table; it would probably be deflected to the left or the right or maybe even straight back to you. The exact same thing happens with light: when it strikes the surface that’s bumpy at the molecular level, it can bounce in pretty much any direction.

Most dry surfaces are pretty bumpy, but water likes to lie flat and isn’t as bumpy as those surfaces. When light strikes the water, it’s more-or-less deflected all in the same direction because now the surface is much smoother. This is why wet things are shiny: because the water is making the surface smooth (again, on a molecular level) which makes any light that strikes it reflect not randomly, but in the same direction.

Concluding, in order for things to look shiner when they are wet, the surface needs to be even and flat, let alone smooth. The smoother and even the surface is the shinier and glossy the surface will look when it is wet.