If your printer has the white ink option and white is not printed on a regular basis, pigment settling can occur in the white ink printheads. During periods of white ink inactivity the printer will automatically try to maintain the white ink channel using the following methods:
ink recirculating
spitting
AMS cycles
Additional efforts may be required to recover nozzle performance for the white ink printheads.
Wear eye protection and nitrile gloves when handling or cleaning ink. Also, when working around ink protect your clothing and any exposed areas of skin.
Equipment
Safety glasses with side shields
Gloves (for example: Ansell Microflex 93-260)
Foam Tipped Swab (3010118211)
Cloth-Poly Wipe 10cm x 10cm (lint-free)
Isopropyl alcohol - IPA (>= 98%)
A general guideline is to do a standard AMS on the white ink channel if:
more than 2 nozzles outs exist in a single printhead
2 or more adjacent nozzle outs exist in a single printhead
more than 4 nozzle outs exist in a single color channel