HOW TO REFILL A CANON BCI INK TANK
Here shows an empty BCI-3C (Cyan) ink tank. The best way to inject the cyan ink is a hole 1/8 of an inch from both top border and center divider (use inner edge), as the yellow dot shown on the picture.
Find your own best way to punch a hole on the ink tank as long as it is a smooth one. I prefer to burn a hole. As the picture shown here pre-heating a pushpin with candle light. The next picture shown a clean burn hole. You also need to make sure the surface around the hold is smooth by using a knife the trim any bump around the hole.
A hole 1/8 of an inch from both top and center divider edges (the inner edges).
Here shows using a knife to trim bumps to keep the surface leveled and smooth.
Injecting ink into the tank is a bit challenging compared with other steps. The goal is not to let ink seep from the nozzle at the bottom and not to let air bubble coming out of the injecting hole to create a mess. The way to do it is to hold the tank with the nozzle on the top so the ink will not come out while you injecting the ink. Make sure to try your best to avoid air pocket when you suck the ink out the ink bottle (a few practice will do the job).
Here shown a successfully filled ink tank.
Make sure you use a piece of tissue paper to dry the entire area around the hole. Any moisture will prevent the hole from properly air-sealed and will create ugly leakage in the future. Use a piece of Scotch tap to seal the entire area as the following picture shown. Use your fingernail to drive any air bubbles out the the taped surface, this is crucial because any air leakage from the hole will certainly drive excessive ink into the nozzle and the printer will be unusable.
Wrap the tape around and put the ink tank back to the cartridge holder.
Finally, don't forget to click the "Cleaning" under "Maintenance" tab in the Printer Setup. That's it! I have tried many different ways to refill the ink tank but so far this is the best and simplest way to do it. As you can see the beat-up ink tanks in the cartridge holder, I don't remember how many times I have refilled them - a lot I would say. These are still the same original tanks came with the printer I bought a year ago and the printing quality still good. Bottom line... it costs me less than 50 cents to refill the tank while Canon charges around $12 (plus tax) per tank - a bit expensive don't you think?!