HP Ink Question????????

[newavemark]

I have a HP 78 cartridge that was used once thirty days ago. After that use, I placed the protective film back over the ink heads and put it a dark cabinet. Upon taking it out yesterday, my print colors are now off. It looks as if my "yellow" has somehow changed to brown. The thing I do not understand is why it would change colors over a short time with the protective film over the head. The HP 78 is a multicolor(c,m,y) inkjet cartridge that I use in a Microboards cd label printer.

I had a second cartridge that I used about the same time and did the same procedure with (film, cabinet, 30days) and the yellow has turned green. I understand the cartridges are probably toast but what did i do wrong so I dont run into this issue again? Why brown?Green?

 

[mikling]

There are two possibilities.
1. You overfilled the cartridge and the protective film was not put on properly. Thus when the ink leaked down, it crossed contaminated over to the other colors from the outside of the nozzles.

2. The bottom plate on the HP78 are notorious for a weak bond. In effect, when this bond is compromised, ink that is next to each other leaks across to other colors from the inside right at the bottom of the plate/printhead and then cross contaminate. Even if the bond was good before refilling, if you used some sort of priming device with too much pressure to pull the ink out or if you use pressure from within the cartridge to push the ink out, this might be enough to break the bond and allow ink to seep across colors.

The Hp78 are best refilled within a vacuum chamber.

Most times when cross contamination occurs on thermal heads it is because of the bottom plate coming unbonded. Thsi will even happon on Canons but the HP78 is notorious for this weakness.