Canon inkjet printer ink tanks have various reference codes printed on their labels. One type of code that appears mid-label is a one to four character generic code printed on a horizontal bar in bold font. This code describes a specific ink color and ink type. The "PGBK" and "BK" codes are two separate examples of this type of code.
PGBK and BK Defined
The letters "PGBK" refer to Canon pigment black ink -- the primary black ink used to print documents that feature mostly text instead of images or pictures. The ink is also often referred to as "Page Black" ink. The letters "BK" refer to Canon black dye-based ink -- the primary black ink used with other color inks to create rich, high-quality images and pictures.
Canon "PGBK" pigment black ink is bleeding and smudge resistant, and it adheres and dries on most print materials quickly. Once it has dried it's also less prone to fading. On the other hand, the ink doesn't work well on glossy or coated print materials such as photo paper. Canon "BK" dye-based ink is used with other color ink because dye-based inks offer more color options and higher color contrast. It also works well with photo paper.
Canon notifies users of differences between ink tanks with the "PGBK" and "BK" codes as well as with separate part numbers. The separate part numbers come in two forms: "Canon" followed by numbers above the "PGBK" or "BK" section, and a more detailed ink tank part number used for reference purposes printed below the "PGBK" or "BK" section. You should always reference the ink tank part number when discussing the tanks with a repair person or purchasing new tanks. Although many Canon printers have "PGBK" and "BK" tanks, different printers use different parts. Part number examples include "PGI-220BK" -- number for a specific pigment black ink tank, and "CLI-221BK -- number for a specific dye-based black ink tank.
Most Canon printers stop working when any ink tank empties. Even if your printer uses both "PGBK" and "BK" ink tanks, you usually must replace the empty tank to continue printing. In addition, a Canon printer is designed to work with a specific tank in a specific slot. If you purchase generic ink and put the wrong tank into the wrong slot, or try to modify your Canon printer to accept one ink instead of the other, you can clog or damage the printer.