What is the difference between PBT and ABS plastic?
"PBT plastic is different from its shiny ABS counterpart. PBT has a much higher melting point, therefore can be treated with a process called 'Dye sublimation'. An image is printed on a film, the film is then laid on the keycaps, a press closes, and the image sublimates into the plastic. Sublimation by definition is when a solid rapidly changes to a gas, by which the gas saturates the hot plastic. The legend is therefore dyed into the plastic forevermore.”