Epson STYLUS PHOTO R2400 Manual page 252

Below are two sample nozzle check patterns.
Good sample
Print head needs to be cleaned
The above sample is in black and white, but the actual test prints in color
(CMYK).
If the nozzle check page does not print satisfactorily, there is a
problem with the printer. This could be a clogged ink nozzle or a
misaligned print head.
Cleaning the Print Head
If you find that the printout is unexpectedly faint or that dots are
missing, you may be able to solve these problems by cleaning the
print head, which ensures that the nozzles are delivering ink
properly.
You can clean the print head from your computer using the Head
Cleaning utility in the printer software or from the printer itself
by using the printer's control panel buttons.
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Improving Print Quality