Epson cartridges are not empty

[mcm]

I have purchased a refillable cartidge set for my Epson 7900 from Inkjet Mall and have began to replace my opaque Epson 700 ml cartridges (at $280 ea. from Epson) as the printer tells me that I should replace a color. I replaced it with Cone Color Pro ink in a refillable cartridge. Imagine my surprise when I pulled the supposedly empty Epson cartridge to find that it still contained 350 ml in it! There is a reason why the Epson cartridges are opaque. Thanks Jon Cone and Inkjet Mall for giving us such a wonderful option!