Last night, Dennis told me about a simple check he uses on his printer to check on banding or blocking of the ink cartridges.
He has a typed out and stored a simple one page document showing each of his printer cartridge colours in large heavy font. For example, this version matches the six colours in my own Epson printer.
He simply prints this out and checks for signs of banding or ink supply problems in each of the colours. He then knows when to clean the printer nozzles or change a cartridge.
Simples! Thanks to Dennis for this tip
Note: Some printers have a built in utility for a nozzle check which does a similar job. For example Epson printers usually print a nozzle check pattern as shown below, with wavy lines for each of the cartridge colours.