Select System Preferences (or System Settings) from the Apple menu > Printers & Scanners (or Print & Scan or Print & Fax) and then select the printer.
Click Options & Supplies > Utility > Open Printer Utility.
Click Print Head Cleaning > Power Cleaning.
Follow the on-screen instructions.
If print quality has not improved after running Power Cleaning, wait for at least 12 hours without printing (we recommend turning off the printer), and then run a nozzle check. If print quality has still not improved, run Cleaning and a nozzle check again. If it has still not improved, run Power Ink Flushing.