Canon printers have two types of sponges. One is in the cartridge and another is an ink absorber. These are both important to clean as it is necessary for proper function if you have been refilling the cartridge it frequently, or printing a lot of pages. This should take at the most 20 to 30 minutes. And, you will save money in the long run by cleaning and refilling your own cartridges.
While there are many different types of Canon cartridges, this article will focus on a general Canon cartridge.
If you have not already done self-refilling on the cartridge, drill 2 holes: one on the top and one on the bottom. Drill over a sink, where you can wash the ink away. Also, wear gloves or the ink will dye your hands.
Notice that this cartridge has two chambers. The lower chamber has a sponge. The upper chamber is an empty ink reservoir.
Extract the ink from lower chamber by drilling your first hole in the cartridge and extracting with your syringe. Make sure that you don't push on the sponge, or it will ruin print capabilities.
Drill the next hole in the upper chamber and extract the ink.
Take out the sponge by prying the top off with a flat end screwdriver, or butter knife. This will take some working at it, but eventually it'll come off. If you do not want to do this part, you could inject water into the sponge and then extract it, repeating this until the sponge is clean.
Once the sponge is out, wash it with just a little drop of soap and water. When the water comes out clear, you can squeeze it dry.
Put back in the sponge and make sure to push the sponge down onto the inkhead. Then, put the top back on and secure with tape. Tape up the bottom hole that was drilled so ink does not dribble out, and refill with it ink.