Canon PIXMA MG2525 All-in-One Inkjet Printer (Black) - Manual (Page 151)

Back of the Paper Is Smudged
Check1 Did you confirm the paper and print quality settings?
Print Results Not Satisfactory
Check2 Perform the Bottom Plate Cleaning to clean the inside of the machine.
Cleaning the Inside of the Machine (Bottom Plate Cleaning)
Note
• When performing duplex printing or too much printing, the inside may become stained with ink.
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