Why Clear Cases Turn Yellow and How to Avoid
We all love clear cases because they showcase the beauty of our phones. For this reason, most people have two or more phone cases, one of which is a clear case or has a clear back cover so that they can always be reminded of the beauty of what their hard-earned money got them.
But why do they turn yellow/Brown?
Ah, the age-old mystery of the yellowing clear phone case! It’s a common frustration, and while it might seem like your once pristine case is simply aging poorly, there’s some interesting science at play.
The primary culprit behind this discoloration is a process called oxidation. Many clear phone cases are made from a type of plastic called thermoplastic polyurethane (TPU). This material is popular because it’s flexible, durable, and relatively inexpensive. However, TPU contains polymer chains that react with ultraviolet (UV) light from the sun and even artificial light. This exposure initiates a chemical reaction where the material begins to break down at a molecular level.
Think of it like this: just as oxygen can cause metal to rust, it can also cause TPU to undergo a chemical change. This change results in the formation of new molecules that absorb light differently, giving the case that characteristic yellow hue.
A Piece of metal having undergone oxidation.
Another contributing factor is the oils from your skin and the environment. Every time you hold your phone, natural oils and sweat transfer to the case. Dust and other tiny particles in the air also accumulate on the surface. Over time, these substances can become embedded in the TPU and, through further chemical reactions or simply by staining, contribute to the yellowing effect.
Heat can also accelerate this process. Leaving your phone in direct sunlight or in a hot car can speed up the oxidation of the TPU, making the yellowing appear more quickly and intensely.
While some manufacturers are exploring materials and coatings to mitigate this issue, the fundamental chemical properties of TPU make it susceptible to yellowing over time. So, while that clear case looked fantastic when you first got it, the eventual yellowing is often an unavoidable consequence of the material’s interaction with light, heat, and the environment.
How do you slow down your clear phone case from turning yellow?
There are many ways to prevent your phone from turning yellow. They start with preventing exposure of your phone case to the above-mentioned factors that make your phone turn yellow, and end with using a completely different material for your phone case.
A photo showing a TPU transparent phone case (left) vs a Polycarbonate (PC) transparent phone case (right).
Ways in which to slowing down yellowing are:
- With clear cases, it is important to prevent them from being exposed to too much UV light, that is, sunlight, fluorescent lamps, and LED lights, by covering them with an opaque material or putting them in pockets if you are out. It is also important to use clean hands to prevent the case from being exposed to oils and dirt. Using your phone in a cool, dry place will also definitely help slow down yellowing.
- It is also important to note that all TPU cases will turn yellow after a while, and the above methods only slow down yellowing. One good way to substantially slow down yellowing is by buying a phone case made of transparent PC material (Polycarbonate) or Acrylic (Hard Clear Cases). PC or acrylic case have strong bonds in them which slow down the chemical reaction that would make them to oxidate faster. These clear cases are, however expensive than their TPU counterparts.
It is important to note that most clear cases turn yellow eventually. In recent times, some manufacturers have made phone cases with clear covers that have been promised not to turn yellow in their entirety for their lifetime, but we are yet to confirm this.