It is important to avoid air bubbles from forming in the lower sponge, so we suggest that you insert the syringe needle through the exit hole and fill the sponge from the bottom up.
The precise location of the hole in the upper reservoir isn't important. What is important is that the seal be air-tight when you finish -- otherwise you'll have a slow leak.
This cartridge does not have a printhead -- only an ink reservoir.
Step 1) Put the cartridge on some paper towels in an area where you can tolerate a spill.
Step 2) Inject a small amount of ink into the sponge through the ink exit hole S-L-O-W-L-Y until the sponge is saturated. This will reduce the chance of an air bubble forming and blocking the ink flow.
Step 3) Remove the label and drill a 1/16 inch, 1.5 mm, or #55 hole directly opposite the original fill hole (the one with the steel or catridge ball).
Some people simply push the ball into the cartridge and fill through this hole. That's ok, but can make an annoying rattle.
Step 4) Inject the cartridge with about 8-9 ml of ink (about 1/4 of a syringe bottle. Fill S-L-O-W-L-Y to fill the entire cartridge. Rotate the cartridge as you fill to remove air bubbles.
Step 5) Seal the hole with hot glue, hot wax, silicone rubber, or (if desperate) electrical tape. You need to get a good air-tight seal or you will develop a leak. You also need to get the seal flush with the surface.
One of our customers recommends placing a 3/16" x 8-32 fillister head (pan head or round head will also do the job) screw to seal the original fill hole.
Step 6) Set on a paper towel for an hour as a drip precaution. Expect a few drips -- the ink must drip for the sponge to be full. Cover all holes during storage to prevent leaks and evaporation.
Follow the directions in the inkjet manual.
Run the printhead cleaning software.