want to make that old yellowed ABS armor white again???   the yellowing is caused by a chemical reaction in the plastic (caused by the flame retardant used in ABS reacting with UV sunlight) but fortunately this reaction is reversible. and can be done at a reasonable cost and effort (actually easier than buffing painting sanding ect..) just by making a gel called retr0bright (DO NOT USE BLEACH!!!!)i have never done this personally but you can search google for retr0bright as well and se