Why old computers turn yellow

Ever wonder why old computer equipment—original Macs, Apple IIs, Super Nintendos, and other relics of the '80s and early '90s—turn yellow with age? Vintage Computing and Gaming has a fascinating trip into the past that I just discovered  (even if the story is over a year old).

The case studies are curious, showing otherwise identical Super Nintendo consoles, one that looks practically new, one which has turned a hideous, vomit-toned shade of yellowish brown. One machine is obviously of a newer vintage than the other, so what happened to the older one to make it change color so dramatically?

One man looked into the matter, and the investigation starts with the obvious and traditional culprits: Exposure to ultraviolet light is commonly fingered as the suspect, but photos show that the effect is not limited to the outside of the case: Even the interior of the old Super Nintendo in question is uniformly yellowed. In the linked story, a Nintendo rep offers one (possible) alternative: A flame-retardant chemical in the plastic causes the discoloration over time when it's exposed to heat and light.

Still unhappy with the explanation, our expert turned to professional chemists and plastic experts to get to the truth of the matter. While light and heat are accessories to the crime, the truth involves oxidation: The simple exposure of the plastic to the oxygen in the air. Over time oxygen attacks a chemical in the plastic and causes it to degrade. When oxygen adheres to the molecules in the plastic, a different chemical is formed as a result, and that chemical has a yellow tinge to it. (Read the full text for more details if you're a true chem geek.)

As for what can be done, not a whole lot. Removing electronics from an oxygen environment is largely impossible, so the only thing that can really help is to put some kind of coating on non-degraded plastic to keep oxygen from getting to it. UV-resistant clear coat is available in spray cans. Other preservation methods (and repair suggestions for those hoping to restore yellowed machines to their former glory) are also available if you click on through to the full story.

LINK: Why Super Nintendos Lose Their Color: Plastic Discoloration in Classic Machines