Does anyone know of a company that supplies grey and (seperate) black ink jet cartridges that allow accurate tonal range when printing black and white? I really don't want to use commercial print shops as I am rarely impressed by their quality. My printer is a HP photosmart 7350. I know that HP don't do them for this model but wondered if anyone else did.
Grey ink is very specialised and only works in printers designed to use it.
I'm not familiar with your printer model but, do the makers say that grey ink can be used in it? If yes then they should be able to supply the ink. If no, where are you expecting to put the cartridge? Be aware as well that the software must be able to accommodate the presence of grey ink.
Your comment about commercial print shops may or may not be true but, if you are dissatisfied with their work, complain. Only then will these people improve their services. Also, there are lots of print shops out there wanting business. If one can't produce satifactory results, go to another.