How do you unclog a printer head on catridge? -

I have a HP deskjet that does not print black. I think the head may be clogged how do i fix this?

Take out the cartridge and run hot water over the jet bit at the front for a minute or so. Then press a tissue over the jets with your finger and flick it in a downward motion a few times. You should see the ink leave a pattern on the tissue. You might have to do it a few times. Another way is to hold the jets over steam then do the same test. You have to be careful not to damage the contacts, but most cartridges are hardier than they look