Filling CMY cartridges with black ink to get opaque black?

[BlueToBits]

That is also what I think. The dye black (photo black) was introduced to improve black and very dark colours. Dye CMYK printers can produce "Darker blacks" than dye CMY printers can.

How about flushing the pigment black cartridge and refill it with dye black and then select plain paper as printing medium to use the pigment black cartridge? Then you would not get the CMY channels in the print head contaminated with black ink that might take some cleaning to get rid of.

I assumed the black cart was already dye based ink. That's a good idea. I have the extra print head, a bottle of IPA (iso prop alcohol not india pale ale ) and a compressed air supply so cleaning the head is not too difficult. My thoughts were that if the black is made up of CMY (+ K), given the opacity of the each of the CM&Y is pretty poor, if I put black ink in these carts I should get a deeper black. It seems that the printer won't care, I may be killing the printhead as far as future colour printing goes, but it's a spare anyhow. I was just a bit worried about cross contamination if there's an "excess ink wiper", "head seal" or "overspill tank" that may put black ink from the modded print head onto the colour print head.

 

[BlueToBits]

Maybe you should consider using a Laser printer, you’d have better success with that...

I tried a few laser printers a cheapo desk top, a big commercial one , one at our local library and one at a commercial printing company. Prints look fine until you hold them up to the light. none of them were any better than my inkjet. However, I only had access to experiment with settings on the cheap one here in my workshop so I haven't ruled laser out completely, I will have find one that will allow me to turn the toner density right up.

 

[PeterBJ]

A concentrated alcohol is not a good print head cleaner. It can act as a desiccant and extract water from a clog, making it harder to dissolve. Diluted alcohol is much better for this purpose, and here is a recipe for pharmacist's cleaning fluid that is very popular on this forum. A window cleaner with ammonia is also good for print head cleaning.

The print head in your printer is very similar to some print heads used by Canon, and the same cleaning methods can be used for instance this.

Both the Canon and HP print heads have separate sections for pigment and dye inks, so filling black ink in the cleaned pigment black cartridge should cause no cross contamination from the purge unit/cleaning station, else the normally used pigment black would have also have caused problems.

As the cleaning station in your printer doesn't normally cause cross contamination between cyan, magenta and yellow, I think no harm will be done by using the printer with 3xdye black instead of CMY. I think a few print head cleanings will be sufficient to replace the black ink with coloured ink when you change back to CMY inks.