In every town centre there is a cheap shop which will most likely sell a cartridge refill kit for either £1.99 or £2.99 and each kit will refill a colour cartridge about 4 or 5 times. A Black refill kit will refill the cartridge approx. 10 to 12 times.
I have been refilling cartridges for about 12 years now and the cartridges I bought with my latest printer were refilled for just under two years, total cost of refilling?? - approx £5.00. Before starting to refill, cover the area with plenty of newspaper and, if necessary, wear rubber gloves.
It can be messy at times but you get much better with practice and saving loads of money makes it all worth while. Also, never let the cartridge completely run out, always check and refill early.
Using either a wooden cocktail stick or a sharpened match stick, locate a depression in the plastic label with a thumb or finger nail and then pierce the label with the stick to find the right colour of ink needed for that particular filling hole.
Using the supplied syringe, gently and slowly refill that particular part of the cartridge. If the filling ink starts to show at the filing hole or floods out of the bottom at the print head, then suck about 1 cc back into the syringe. Each compartment has a certain amount of sponge in it to soak up and retain the ink so if you inject too much ink it is bound to flood out.
Repeat the above for the remaining colours (Yellow, Magenta and Cyan).
Always clean the syringe between using different colours.
Draw a plan showing which hole is for each colour for future reference.
Now make a document file with three rows of capital letters, making one Yellow, one Red and one Blue, then print out the document.
If any colour is a bit feint or has pale lines running through it, stand the cartridge in a scaucer of hot water (not boiling) until cool and then wipe the print head with a paper tissue until all the colours show on the tissue.
Reprint the document to check that all colours are printing OK or repeat the hot water treatment as necessary.
The above will save you having to regularly replace expensive cartridges.
Some printers will not allow you to replace a cartridge once it has been removed but there are ways around that problem.
Hope this helps.