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Clean the scanner glass or strip inside the feeder with a lint-free cloth barely dampened with isopropyl alcohol, then let it dry before sending anything. Dust and toner residue on the scanning strip are the usual cause of the black vertical lines that show up on the recipient's copy. Unplug the machine first, never pour liquid inside, and repeat the wipe when lines return.
The classic sign is a thin black vertical line running down every page the recipient receives, while your original looks clean. That line is a speck of dust, dried ink, or a flake of correction fluid sitting on the scanning strip: because the page slides past that exact spot on every pass, the speck draws a line down the whole image. Misfeeds and pages that skew sideways are the other symptom, usually from dust on the feed rollers robbing them of grip.
Here is the part people miss: the line appears on the recipient's copy, not necessarily on anything you print locally. Cleaning the scanner strip fixes what you send. If your own printouts also show lines, that is a separate path: the print drum or toner cartridge, not the feeder. Fix the sending side first, then check a printout to see whether the second problem is real.
| Do | Don't |
|---|---|
| Unplug the machine before you open anything | Clean while the machine is powered on |
| Use a lint-free cloth, lightly dampened with isopropyl alcohol | Use paper towels, which shed fibers onto the strip |
| Wipe the scanner glass or strip gently, in one direction | Use window cleaner with ammonia or any abrasive pad |
| Let the strip dry completely before feeding pages | Pour or spray liquid directly inside the machine |
| Check the feed rollers for the same dust while you are in there | Touch the strip with bare fingers, which leave oils |
The alcohol matters because it evaporates cleanly. Water leaves minerals behind, and household cleaners leave films that smear the next scan. If you have a can of compressed air, a short puff clears loose dust from the rollers before you wipe, but hold the can upright: tipping it sprays propellant liquid onto the parts you are trying to clean.
Lift the document feeder lid and look at the narrow glass window the pages slide across on their way through. On flatbed-style machines there is a separate thin strip beside the main glass; on feeder-only models it is the single window under the lid. Either way, it is a strip of glass a finger wide, and the speck causing your line sits somewhere on it. Wipe the whole strip, not just the spot you think is dirty, since the offending speck is usually invisible.
Clean when the symptoms appear, and otherwise about once a season in a normal office. Dusty environments (workshops, mail rooms, anywhere near a paper shredder) need it more often. Offices that still use correction fluid or heavy highlighter should wipe the strip after faxing marked-up pages, since white-out flakes and highlighter smears are the most common stubborn contaminants. A five-minute wipe every few months beats an afternoon of re-faxing ruined pages.
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