What kind of printer? Anything you can say would be helpful, personally I've experienced this once before, all it needed was a bit of cleaning, and the manual that came with the thing explained that. If you can find a manual for the thing it might be more useful than our speculations(but of course that's not always true).
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Would that smear be on the cartridge bay side? If so, it may be because of build up of ink that has collected and filled the evaporation tray and leaked over the side, this then smears the paper. I have an old HP printer that does this from time to time and its either that or fluff and hairs shed from the cat that are the cause.
How I used to deal with this problem was to put the printer in to the cartridge access mode, usually lifting the lid on the cartridge bay will do that for you but on chaper printers its often a button press for which you will need to consult the manual.
1. Check the ink cartridge caddy is not fouled up with ink and hairs, etc.
2. if this appears to be the issue, clean using kitchen towel and cotton buds where access is difficult then try a test page when you have cleaned it.
3. using similar processes applied to the caddy, clean the inside of the printer with kitchen towel and especially where the caddy rests when not printing, this is possibly where most of your issues may lie, thats what I found with my HP printer when it started streaking the pages.
4. paper... not many people know this but paper has a knap to it and if your paper is loaded wrong and it absorbs moisture from the air, it can have a slight curl in the wrong direction and then you get streaking. in a photocopier & laser printers, this wrong loading results in a paper jam.
You can in most cases use an alcohol based cleaner with care. if you do then get a pair of latex gloves and avoid skin contact.
Alcohol is readily absorbed by the skin and the component that is put in to it to stop you drinking it is also poisonous like the alcohol so use with care. No smoking or naked lights and ensure your in a well ventilated area like an open garage.
If its giving you a real headache, remember that cost of printers has plumeted. I got fed up with my old HP that much, I replaced it and that only cost me £29 ($50~ish) for an Epson D92 which does the job for me and does print a nice picture on proper photo paper for the price of it.
Why is my printer putting smudges of ink on whatever I print and how do I fix this?
Ink drying of various processes, said Hugh J. Price, editor of the production planning. Linseed oil inks dry by oxidation in air, which solidifies the vehicle. Ink with solvents or alcohol petroleum-based dry by evaporation, often assisted by heating the paper.
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