system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do some old plastic appliances fade to an off yellow colour after many years?
gpt
Most plastics contain substances that make them burn slower, for safety reasons. These flame retardants use the element Bromine. When the Bromine remains bound up as the flame retardant, it is colourless, but when it breaks down, the remaining bromides are a bright yellow. The main thing that breaks these flame retardants down is ultra-violet light, but heat and other chemicals can also do it.