In cups webinterface localhost:631 switch to Printout Mode tab page, there you can select Color Mode: Monochrome and Resolution: 1200x1200DPI instead of Controlled by 'Print Quality'.
In cups webinterface localhost:631 switch to Printout Mode tab page, there you can select Color Mode: Monochrome and Resolution: 1200x1200DPI instead of Controlled by 'Print Quality'.