Why can’t you print grayscale without color ink? How do you print using PGBK (pigment black) only (thus rendering the first question moot)? Why does Canon use color for something clearly grayscale? Why am I so frustrated? What is PGBK?
The most important question for most people will be “How do I print using only the black cartridge?” There are two reasons for doing this, and I won’t trouble you excessively to find out how.
One is that you are printing a lot of single-sided text and prefer pigment black (it is indeed best for text). The other is that it’s necessary because you don’t have all your ink cartridges full enough.
PGBK is Pigment Black. It’s a separate ink reservoir for certain operations that must be printed with a pigment that’s as black as possible. The CMYK cartridges are dyes and are just not going to make text as black as pigment black.
First, all cartridges must be installed whether they are empty or not. You cannot continue unless this is the case…so dig through the trash if necessary.
If you have an ink warning, you can dismiss it by holding down the red button until the message disappears. This should be around 10 seconds. If it isn’t working, check for another red button or one that says “stop” or something similar and use that instead.
How to print using PGBK only
The procedure for using pigment black only is fairly straight forward. Canon has it documented well enough here, so I don’t feel the need to repeat it. You basically go to printer settings and choose grayscale.
It’s almost as simple as that, but if you use duplex mode the grayscale option is silently ignored. The rationale has to do with ink smearing, but I’m not sure if I buy that. Either way, you cannot do duplex printing with pigment black only, even if you choose manual duplex. So, in order to cut down on paper waste, you have to use expensive ink and sacrifice print quality. Thanks Canon.
Composite versus PGBK for grayscale
However, that’s not the end of the story. I didn’t even answer the question for the article title. I wanted to know why color ink is used for grayscale, so I made some tests. I’m going to start out by using this test ramp pattern, printing in color, printing in grayscale, and then taking a look at a closeup.
And after scanning it in, we get this:
Well, the pigment black looks sort of fucked up, doesn’t it? But it will suit my purpose.
Comments about the results
With colors enabled, at 100% pigment black appears to be used. With pigment black looking black and composite black looking like a dark blue and the transition between them not being smooth, it definitely seems like a good idea to avoid full black for a photograph. Apart from that, each color looks smoother since dye can be used to transition instead of increasing the dot spacing. Although it retains a blue sort of tint, it manages to show distinct color bands on my monitor until 90%.
For pigment black, my printout is abominable. It continues to get darker the closer to 100%, but it doesn’t seem quite as distinct as the composite test after 80% or so. It looks as if the gradient is made up of bands of alternating intensities, which doesn’t make much sense to me.
A thought about the PGBK print nozzle array
The pigment black nozzle array is as long as two steps on the stepped gradient, which is also twice the length of the composite nozzle array. That arrangement of nozzles allows pigment black pages to be printed relatively quickly. By the frequency of the white streaks, which occurs every 2 steps, this appears to have been printed using the whole length of the nozzle array. Based on what the alignment test looks like, high quality print mode uses only the best looking set of contiguous nozzles, meaning standard quality grayscale quality is wholly dependent on the state of all your pigment black nozzles.
Oh, I found a better way than deep cleaning to clean the composite print nozzles, but I’ll save that for another post. It doesn’t even require removal of the print head or the use of solvents, etc.
Just a little closer…
It’s not the main question here, but it looks like the composite side doesn’t get dark enough at 5% like the pigment black does. It might be the fault of my manual color adjustment to make things lighter, as CMYK printing tends to make dark areas so full of ink it starts to pool a little bit.
It looks like composite black is a little too light at the low side. Pigment black’s grainy looking dots are easily seen. Well, there’s nothing profound here.
It all adds up to this…
I’m not convinced about the smearing justification for using color to print black text in duplex mode, especially in manual duplex mode where there is ample time for ink drying. It could be printed in reduced quality mode to use less ink or something. Printed text doesn’t look as good as if it was printed with pigment black — sort of black but never really black. But using pigment black in a color document would not look right either because it couldn’t provide the same sort of look across all shades.
So for text printed in regular mode, using color is acceptable, since you have the option of telling the printer not to use colors. I don’t think it’s acceptable to refuse to use pigment black when printing on both sides. That is likely when someone would print a higher volume, so it makes good business sense to force them to use color ink when doing so. However, such actions are unacceptable.