MIS instructions for refilling Epson carts for my old Stylus color 900
involved using a 60 cc syringe and pulling a vacuum on the bottom of the
carts to remove as much ink foam as possible from the sponge material and
then injecting the ink into the exit port with a bottom-fill adaptor to a
leur-lock syringe. this was an extra step they suggested because of the
retention of air and ink in the sponge which it retained in a foamy state,
preventing absorption of ink when refilling. Canon carts, on the other
hand, have the reservoir adjacent to the sponge area from which the ink is
drawn, first into the sponge and then through the exit port on demand for
printing. OEM Canon carts have two different densities of sponge in the
cart, one on top of the other. This system seems to control ink flow better
than some of the attempts at new and innovative design, one of which is
spongeless. I am currently using MIS carts that I purchased empty and am
refilling. They have the more typical single piece of sponge that non-OEM
carts have that takes up refill inks more readily than the OEM carts and
work quite well. I have seen a series of posts on a spongeless Canon bci-6
cart used for refilling that was glitchy and sometimes didn't feed well. I
think that you are right in that the sponge in the Epson carts presents a
problem for refilling.
Another series of posts delved into the problem of Canon carts failing to
feed properly after several refills. It appears that some ink solidifies
near the exit port and prevents ink from feeding on demand. As an
experiment, a very innovative person backflushed the non-functioning carts
with hot water, vacuumed out the water, let them dry, and refilled them.
They then worked just fine. Not practical when you consider the low cost of
aftermarket carts that are designed to be refilled, but an interesting
experiment in cart function. While someone may criticize this as a waste of
time and "tinkering", it certainly adds to the base of knowledge for solving
problems when they occur.