The air in the reservoir chamber has to go somewhere when you refill ink. It seems that it leaves the cart through the big hole at the bottom without forming any bubbles (maybe because of the special materials of the small sponge/filter there? Or just because the hole is so big?), but if you put the orange clip back on, the tiny refill hole and the ventilation labyrinth on top of the cartridge are the only exits for the air. I don't know, but it seems that small spaces help building (unwanted) bubbles.sneezer2 said:In these two instances I had replaced the orange "clip" and secured it with a rubber band, a legacy of my previous
method where you need that in place. I suspect that may be the problem but I don't know why.