The priming station of a typical inkjet printer (e.g., HP DeskJet 500C) includes a rubber seal ('boot') and small pump to actually suck on the end of the print cartridge to free up nozzles (there are 50 or more in a typical print cartridge) that have dried up or become clogged. It may fire all the nozzles at some point during this process as well. It also includes rubber 'flappers' which the end of the cartridge pass over to wipe off excess ink.
Priming and cleaning are normally done automatically upon power-on and possibly between pages. However, additional cycles may be needed at times.
With the water based ink, even if the printer is powered off properly which seats the cartridge(s) on a rubber seal, some evaporation occurs so priming will often be needed after it sits idle for a while. Note: Don't kill power to an inkjet printer as soon as your printout pops free - it needs to position the printhead and cartridge(s) on the rubber boots. Wait until the printhead stops moving and clunking. Some (older) printers don't even have a seal in which case letting it sit idle is even more likely to result in problems.
If there has been ink spilled into the priming area, it may clog up the little hose connecting the priming station to the pump - I have used a wooden toothpick to clear the hole though this may be risky if it should break off. With care, a wire rounded off at the end so as not to puncture the tubing can also be used. Complete disassembly and washing of the parts is probably the best but is probably a pain. Search below for great deals on all of your printing needs, including inkjet cartridges, toner cartridges, ink refill kits, cleaning cartridges, printer paper, and much more.
