Sometimes - and beat us, we don't know why this happens - ink cartridges suddenly decide to start playing up.
If you find that your prints are blotchy and jarred, but the cartridge isn't empty, your beloved printer may have fallen prey to patchy ink syndrome (OK we made that condition up, but you get the gist).
Here's some possible reasons for patchy ink even when your cartridge isn't anywhere near empty.
You've just changed your ink or toner cartridge
On buying a new ink cartridge, it might not work when you first put it into the printer. This can be for a number of reasons – it's a new cartridge, for example, or there's a problem with the print head.
The best thing to do is give the ink cartridges a right good shake first off - honestly, this usually works! But if it doesn't, it could be for one of these other reasons.
There's something up with the print head
Problems with print heads usually happen when old cartridges are taken out, because air can enter the print head, disrupting the ink flow. However, this isn't a biggie.
Nearly all printers will have a 'clean print head' function built in to them - have a read through your printer's manual or fiddle around on the menu screen (that's what we'd do) to find out how you can access it.
The clean print head utility flushes the fresh ink through – you might find you need to run it a few times, though. Another issue is that you might find there's something lodged in the print head somewhere that's affecting a proper flow of ink. Grab hold of some tweezers and remove the offending blockage.
Remember too that print heads are sensitive, so make sure you treat them with care.
You're neglecting your printer
Have you fallen out with your printer? Haven't spoken to her for a while? Not printing regularly is a common cause of problem prints because the ink can dry up.
You don't have to start printing like a madman, but consider running a few sample prints every couple of weeks or so, just to keep things ticking over.