Remove the clogged inkjet cartridge from the printer.

Place in a small dish with print head up and put a few drops of lighter fluid on the print head

Let stand for a few minutes

wipe the print head with a lighter fluid soak cotton swap

pour some lighter fluid over a folded paper towel on a saucer

let the inkjet cartridge sit on the lighter fluid soaked paper towel propped up with a Bic lighter or other item that size so the print head is flush with the lighter fluid soaked paper towel for ten minutes

wipe the print head with a lighter fluid soak cotton swap

soak the inkjet cartridge  in a hot Windex window cleaner for five minutes

put about a quarter cup of Windex in a Pyrex cup on beverage cycle in the microwave to get it hot

soak the bottom of the ink cartridge on an angle instead of instead of print head against the bottom of the Pyrex measuring cup for five minutes

wipe the print head with a Windex soaked cotton swap

put about a quarter of a cup of Perrier www.perrier.com in a Pyrex cup and heat it on beverage cycle in the microwave oven

let the color ink cartridge sit in the hot Perrier for five minutes ink head down on the same angle with out the print head touching the bottom of the cup

wipe the print head with a hot Perrier soaked cotton swab

shake the ink cartridge vigorously for a couple of minutes up and down and sideways to dry off any moisture and to try to mix any freed up ink

then use a paper towel to dry any extra moisture off its contacts and its case but do not touch the print head with the paper towel

then put the ink cartridge back in the HP inkjet printer

run a cleaning cycle

run the priming cycle

Note:  On my HP DeskJet 842C ink printer with new four year old clogged color ink cartridge this method worked.