there are two primary plastics when dealing with keyboards, ABS and PBT

• ABS is really easy to work with and the first choice for doubleshot keycaps but it’s main shortcomings were yellowing under sunlight as it ages, not receiving dyesub printing very well (if at all), and showing shine after regular use
• PBT is very durable and doesn’t yellow with age, but only recently have companies had luck producing doubleshot keycaps, traditionally the legends were dyesub printed onto the keycap (dyesubbing works very well with PBT)

AEK II keycaps were PBT, but the case and the spacebar were ABS (PBT can shrink when molded which can lead to warping in longer keycaps – “banana spacebars”)

for general cleaning

• keycaps are best with just warm water, soap, and an old toothbrush
• for tough spots, a cloth with isopropyl alcohol will work just fine
• isopropyl is also easiest to work with when cleaning switches

for dealing with the yellowing, users on Deskthority came up with “retrobriting” (basically a timed bleaching using a hydrogen peroxide paste) – timing is finicky, best to under do things than over do things – you can usually find more up-to-date videos on Youtube