If your printer is starting to distribute ink unevenly on your pages; the most obvious reason would be a low level of ink or toner. However, before replacing the cartridge or calling a repair person, there could be other reasons that are causing these problems. If you have an inkjet printer, see the first paragraph below for trouble shooting options. If you own a laser printer, see the second paragraph for troubleshooting.

Inkjet Printers:

• Ink cartridge low on ink -Your first step in troubleshooting this particular problem is to check the ink level in your ink cartridge. You may be tempted to skip this step if you think you have not used the ink cartridge enough for it to be low on ink; however, check it anyway. If it is low and you know you have not come close to using the total yield page for the cartridge, the cartridge itself may be faulty. Replacing it will certainly fix your problem.
• Improper installation of ink cartridge – Another cause of uneven printing on a page could be that the ink cartridge is not properly installed. If it was not properly inserted and "locked" into place, and is in fact "lopsided", it will produce uneven printing results on your page. To fix simply take the cartridge out, insert it again and make sure it snaps into place. Then try printing a test page.
• Paper – Check your paper to make sure it is loaded properly and it is not wet, dirty or crumpled. You may want to put fresh sheets of paper into the printer and run a few test pages in order to determine whether the paper is the source of the problem.
• Clogged ink jets – Inkjet technology requires nozzles to eject small blasts of ink to ensure optimal quality and precision, however, occasionally dried ink will clog when the printer is not in use. The clogging will block some ink dots from being applied, thus causing part of the page to be lighter. You can run the automatic internal cleaning routine from the control panel or printer software, which may be able to clear the clog, or you can manually clean the head with Q-tips soaked in water.

Toner Cartridges for Laser Printers:

• Low Toner – The number of pages a toner cartridge will print before needing to be replaced varies among laser printer models. Check your owner's manual or find your printer toner cartridges to determine the page yield for your toner cartridge. The printer manufacturer calculates the number of pages the cartridge will produce on the basis of distributing 5% of the toner over an 8.5" x 11" page. Consequently, if you print a lot of graphics, pages larger than 8.5" x 11" and/or pages with solid backgrounds, you will yield fewer pages per toner cartridge. In order to determine how much toner is left in your cartridge, you can link here to use a tool to calculate your printer page yield, or you can generate a statistics page via the display panel on the printer or from your computer.
• Displaced toner or "clumps" within cartridge – Sometimes "clumps" or uneven distribution of toner within the cartridge produces uneven placement of toner on the paper. You can eliminate either one or both of these problems by removing the cartridge from the printer and shaking it from side to side. Reinsert it and print a couple of test pages to see whether this solves the problem.
• Improper installation of toner cartridge – Sometimes a toner cartridge is not inserted properly and in fact, is "lopsided" which will produce uneven toner distribution on your page. If you find this is the case, remove the cartridge and reinstall it until it "locks" into place. Then, try printing a couple of test pages to determine whether your problem is resolved.
• Paper – If your paper is not inserted properly or it is wet, dirty or crumpled, this may be causing your problem. Simply replace the paper and run several test pages to see whether this improves the toner distribution on the page.
• Drum Replacement or Cleaning– Laser printers have an "imaging" drum that is either in your printer or part of the toner cartridge itself, depending on your printer model. If your printer has an imaging drum separate from the cartridge it will need to be replaced periodically. The rule of thumb is that an imaging drum will have a 3 to 5 times longer life span than your toner cartridge. Like changing the oil in your car, replacing the drum on time will prevent more damage down the road. A statistics page can be printed for the drum just as you would for the toner cartridges which will show the number of documents that have been printed with the current imaging unit. Imaging drums are sensitive to light, so if you remove it, be sure to keep it somewhere dark. Also you can wipe off any dirt or oil that gets on the drum from the rollers. These things can prevent toner from sticking to the drum, thus never be transferred to the paper. If cleaning the drum does not work, it is probably time to replace the drum. If you get through this list and the problem persists, it is recommended that you contact the customer support of the printer manufacturer. They should be able to recommend more detailed troubleshooting tactics for your specific model, or recommend a technician to diagnose the problem.