he Epson cartridges in the very old time that I know of is the S020034 and S020036 which is the black and color (3 colors) cartridges for Epson Stylus PRO. That was in 1996. I never opened those cartridges. Later, I got to know S020108 and S020089 which are the cartridges for Epson Stylus 800. Again, never open those. The common knowledge is those cartridges contain sponge, have no valves and no chips. They are not supposed to be taken off the prnter before they ran out. Since, there is no valve, if you do so, the ink will just about ooze out from the exit. This non-valve cartridge now still can be found in the 3rd party compatible cartridges for the new Epson model.

In the new Millenium (after 2000). I get to know T007 and T009 which is the cartridges for Epson 1280. These new generations of cartridges are chipped (so are Epson 2000P's, 980's, etc) and they contain the valve to prevent the efflux at the exit port. The vent hole was redesigned to be a crooked/wining path (compare to the simple straight hole). The sponge is still there in both dye-based type and the pigment type (T015/T016 for Epson 2000P). These cartridges now allow users to take the cartridge out before it ran out because the valve will keep it closed and the chip has the record of the ink usage. Users can actually change the ink between the printing job. Many people curse the company for the chip that doesn't really read the ink content and seem to prevent the refilling. Moreover, the anger is increased when the users opened the cartridges (which is not recommended) and found a significant amount of left unused ink. At that time, Epson has never made any individual ink tank for the home user printers.

The opened T009 showed the sponge inside.

Then, in the year 2001. The first individual ink tank printer came out -Epson Stylus C80. This is perhaps the pressure from the competitive maker -Canon who is a pioneer in this individual ink tank. The cartridges for C80 is totally different from the previoius models. These cartridges' physical properties are the same as the one for Epson 2200, C82, 960. Only the black cartridge of C80/C82 is twice wider. In this website, we'll talk about the regular size cartridge like the one showed below.

The very first individual ink cartridge of Epson. From outside, it looks like just a simple container. But this cartridge is amazingly detailed and complicated.

Somebody accused Epson of going through all this complicated design to prevent users from refilling which I must believe this is true. Optimistically, the new cartridge also comes with many nice features.

   1) no more cartridge clamp on the printer, the cartridge itself contain the clips to lock itself into the socket. Easily snap in and taken out.
   2) no more plastic cover to peel off. The vent hole will automatically opened when inserted into the socket. The little small plastic piece on the left side is for the air-vent activation. This is the first time that the cartridge is completely sealed off from any air after use and taken off the printer.

Somethings in the cartridge that can be a problems with refill includes
   1) A multi-chamber internal structure (the cartridge is not a single chamber)
   2) The plastic is not a see-thru clear plastic (like Canon). This is probably make the refill blind enough.
   3) The wall that may enable users to do refill are all double walled. (top part). So making hole is a little harder, holding finger to provide a temporary seal is not possible.
   4) The presence of the circular one-way valve right before the exit. To prevent any reflux/air or refilling backward from the exit port. (this could be considered as a nice feature, too).
   5) The internal mechanism that re-route the air vent to open to the lower part of the cartridge.
   6) The presence of internal membrane that may be susceptible to the puncture from needle that used for refills.
   7) The filling port is moved to the bottom wall. Any access for refill for this, need to be resealed again.
   8) The chips is now improved, more resistant (the old resetters doesn't work) and the swedish software doesn't work, either.
   9) the collection of ink in the air-vent reservoir over and over time.

Many of these impeding features turn out to be helpful for a negative pressure refill.