Why can't ink jet print great BW with just black ink?

[Iluvmycam]

My 3880 Epson uses all the colors plus 3 black. Why can't it make a good BW print without using all the other colors?

[Farmer]

Because it (like all inkjet printers) is limited in the number and size and volume of dots of ink that it can lay down which means it cannot achieve all the tonal variations required by using just a single ink.  It also needs to offset the colour of the paper to achieve the tone you desire.

[Some Guy]

I believe some of the reason is that the blacks in most printers have a tint of some sort.  I know the photo black in mine has a purple cast (I made a mess refilling and spilled some and it was purple!) to it so it does use yellow to counter that.  Might have something to do with papers that may not have OBA's in them and a need to counter those warmer papers.

I read something about carbon black being a warm yellow tone so it too needs some color to counter it to neutral black or a cooler tone.

Fwiw, I used to try and save images in the B&W mode in PS, but went back to saving them as Adobe RGB as they sometimes need a bit of color to provide a sepia or selenium bluish tone.

SG

[Randy Carone]

When you print with your 3880 using the Advanced Black & White at least two inks are taken out of the mix. I don't recall which are eliminated but I believe Yellow is one. So, in ABW you are using 6 of the remaining inks, three of which are black/gray with some tinting by the other 3. That's probably as close as you'll get to printing with just black, on an Epson, without using a RIP or modifying the printer/ink.

[Peter McLennan]

I attempted black-only printing with an old Epson 1160 that had failed to a black-only state.

A black-only print must create grey tones by dividing the image into blocks, each one of which holds patterns of dots of black ink.  The more dots in the pattern, the blacker the tone.  A block with no dots indicates white and a pattern half-filled with dots is middle grey.  For a given block size, there is a limited number of discrete patterns of dots available, hence the grayscale is limited.  The tones look "chalky".  Some very contrasty inages can be successfully printed with black-only, but long tonal range images don't look optimal.

A RIP may allow better tonal range from black only prints, but I have no experience with these.

[Iluvmycam]

Thanks for all the feedback.

[Ken Doo]

It sounds like you might like a K7 piezography printer...   

[Ernst Dinkla]

I attempted black-only printing with an old Epson 1160 that had failed to a black-only state.

A black-only print must create grey tones by dividing the image into blocks, each one of which holds patterns of dots of black ink.  The more dots in the pattern, the blacker the tone.  A block with no dots indicates white and a pattern half-filled with dots is middle grey.  For a given block size, there is a limited number of discrete patterns of dots available, hence the grayscale is limited.  The tones look "chalky".  Some very contrasty inages can be successfully printed with black-only, but long tonal range images don't look optimal.

A RIP may allow better tonal range from black only prints, but I have no experience with these.

An Epson 1.5 picoliter droplet printer with 3 or 4 channels filled with a near neutral black like MIS Eboni MK or HP Vivera PK and driven by QTR will make a very acceptable B&W print when the print resolution is set at the best quality possible. The more when the paper is neutral.

The basics:
*the smallest droplets = smallest dots so less visible
*the highest resolution which also forces the printer to use only the smallest droplets
*more channels filled with black = more nozzles to even out banding in one channel + better weaving

Bigger droplets speed up printing which is important for wider machines that will normally print more volume. Hence 17"+ printers with 3.5 - 4 picoliter droplets. Bigger droplets are more visible so there are extra diluted inks LM, LC, LK, LKK for smooth gradations. Wider printers tend to print larger prints that get a wider viewing distance. Bigger droplets have some advantage in precise placing of the dots.

A black ink that is not totally neutral tends to give a more neutral image with big droplets compared to small droplets. The average opacity of a larger dot from center to edge is higher than with a small dot. The total of small dots have more circumference in total and so more dotgain than a large dot (for the same printed area and tone value) which reduces its opacity and the ink hue gets a change to show itself. Like that black will do when diluted with transparant ink medium. Increasing the inkload will reduce white area but not solve the dotgain of the small droplets.

So there are pros and cons but good B&W is not impossible with black only ink.

--
Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
July 2013, 500+ inkjet media white spectral plots.

[Peter McLennan]

Thanks, Ernst. 

My Epson 1160 experiments were interesting and useful, but I can see that newer printers would do much better with black-only.

[blpanther]

One way I have found to 'force' the printer to use black inks only was via efi rip...