I have been refilling these cartridges for over three years without problem. I had a large supply of ink left over from when I was filling Epson cartridges 3 years ago. I bought a new set of refill inks as I figured the old ink was probably not good for the Brother print heads, though I wasn't having any problems. I suspect this new ink is now causing me problems with the black. It started printing faint (gray). I have done several head cleanings and it has improved some, but still not real dark. Anybody know enough about ink to advise me of a good place to buy quality ink in small quantities? All the sellers say their ink is top quality of course. ????