Sorry, steve, that you are experiencing this problem.
According to canon.com's website regarding the i9900 InkJet Photo Printer:
Why color ink may be used when printing in black and white
Even when printing in black and white, color ink is used for the following reasons:
- Automatic cleaning of the print head.
To prevent the print head nozzles from clogging, the print head is automatically cleaned periodically. At that time, a small amount of each color ink is consumed.
Therefore, although printing in black and white is performed, color ink is also consumed.
- Color inks may be used to create black.
When printing in grayscale or on photo paper or when duplex printing, although printing appears in black and white, the color black may be created using the three (cyan, magenta, and yellow) color inks. Printers without a pigment black tank / cartridge will print black / grayscale will create a composite black using color ink even on plain paper.
Therefore, although printing in black and white is performed, color ink may be consumed.
- In order to keep the heavy black ink from smearing on the page or in the printer, color ink is used when duplex printing to help create black text.
I might suggest taking out the color ink cartridges leaving only black there, but some printers don't take kindly to this. So, you may have to further experiment with magenta, cyan, and yellow to make it at least seem b&w to your best eye's judgment.
Good luck on this.