Tech2 has published a guide to restoring inkjet cartridges that have dried from lack of use.
Technology website Tech2 has published a 
step-by-step to recovering dried inkjet cartridges, noting that the problem may be exacerbated during dry weather or during the summer. With a steadily increasing cost of ink and the requirement that cartridges require at least a weekly print in monochrome and colour, these instructions are increasingly necessary.
The instructions and required paraphernalia are taken only as necessary increments: should step one fail to resolve any issues, move on to step two.
Firstly, any lumps of dirt or ink accumulated on the nozzles will need to be wipe clean using a standard ear bud and either warm water or isopropyl alcohol.
If this does not solve the issue, submerge the nozzles in a dish of warm water for as much as two hours. Users are encouraged not to be alarmed at any potential ink bleed: “this is a good sign”. Afterwards, dry and test.
Should this fail to resolve the problem, wipe the nozzles again using a lint free cotton cloth. This should result in some ink smudging, an indication that the ink is flowing. Wipe for approximately five to 10 minutes to ensure free flow or proceed to step four on testing failure.
Step four comes with the caution that it may cause damage to the cartridge: place the nozzles under a warm running tap for 15 minutes. Ensure that the water flow runs over the nozzles and not on the circuit strip. On testing following step four, if printouts result in smudged prints, it may be a result of retained water and Tech2 states that the cartridge may be ready to use again.
However, there is a last step similar to step two, in which Tech2 recommends submerging the nozzles in a saucer of isoprolyl alcohol whilst taking extreme care to ensure the liquid level does not reach the circuit board.
Tech2 is remarkably frank as to possible conclusions: “If all works well, then you have successfully revived your dried cartridge, or else it is time you buy yourself a new one. All the very best!”