White ink is re-circulated in the system to limit any settling of the ink. For this to take place, the printer must be left powered on at all times. Regular maintenance is required to keep the white printheads functioning properly. This may involve additional purge cycles.
Daily maintenance is important even when white ink is not being actively used. Failure to perform daily maintenance can result in nozzle dropouts. The purpose of maintenance is to clean the nozzles of the printheads and thus ensure better image quality.
If your printer includes the white ink option, a white ink bag must be present in order for the printer to function properly.