Cyan produces most of my clogs. IP4200 with home built CISS.

[canonfodder]

So why? Why should one color be the biggest problem? Perhaps the formulation of Canon's cyan for CLI-8 cartridges is different in some property or properties that makes it more subject to some form of clogging. What do you know?

Here is what happens:
With my CIS primed and doing fine nozzle checks, one morning the cyan is partly or totally missing from the nozzle check print.
After much experimentation with unclogging methods, I have found a simple method which seems to work every time.

Here is what I do:
With the printer on, open the top lid to access the ink cartridges. When the printer has moved the printhead to the center for cartridge access, pop out the cyan cartridge. With a large syringe fitted with some tubing* that will fit neatly over the printhead input fitting, pull a good vacuum, resulting in a bit of cyan ink coming out of the printhead. Replace the ink cartridge, close the top lid, run an ordinary color cleaning, and print the nozzle check.

This works almost every time. The printer will continue operating properly for a few days to a week and then the cyan fails once more.

I would prefer a more permanent solution to the clogs, but the big question is still, why cyan and not other colors?

*A short smaller diameter piece to fit the syringe tip and a short larger diameter piece to fit over the smaller tubing and to fit over the printhead input port.

 

[embguy]

First thing come to mind is flow problem. Your cyan may not be flowing as freely as other colors. Is there any back pressure build-up after a few days of usage?

 

[websnail]

I have a quick question...

Which ink are you using and how old is it?

I ask because I've been seeing the exact same issue with my own Cyan, after months and months of Magenta issues and I'm leaning heavily towards either the location of the cartridge or the ink age/viscosity being the issue.

 

[canonfodder]

I am using Image Specialist inks purchased through PrecisionColors.

The ink is getting a bit old now. Probably 2 years old.

I have a new idea about the clogging. It does not explain the color preference, but I think it explains why my un-clogging method is working.

Since I successfully unclog by drawing ink back out of the the printhead ink input, using a syringe and adaptive tubing, I theorize that there is a build up of solids or semi-solids inside the printhead. Sucking the ink out of the printhead is removing enough of the solids to allow proper inkflow. Since the clearing of the clog doesn't last too long, I theorize that I am not removing all of the solids when I suck out the ink.

Remember that I am doing the unclog with the printhead still installed in the printer, so I am not able to feed it any water or other to more thoroughly flush the head. Perhaps removing the head and sitting it in warm water while sucking out the ink could produce a better clearing. I had tried some variations of that before, but did not get great results. I will revisit that someday.