My printer stood unused for about 8 months. Then

Yes - if they are not used they will dry up and be unusable.
Unfortunate but you need to replace them.
For future ref - IF they will not be used in 4 - 6 months
pop them out and put scotch tape on the head where ink comes out
and that should keep them good for several months..
I have done that and close to a year later - was fine.
Hope this helps :)

Start, control panel, printers, your printer, printer preferences, advanced. Uncheck the complete-a-print boxes and also check to make sure the print in black & white box in unchecked.


Rick

Just change the ink cartridges - the print heads are built into the cartridges on this printer. If it sat unused for 8 months, then probably some ink dried in the tiny holes and clogged them. While it might be possible to dissolve it with distilled water, I haven't had very good luck with that. It would be simpler to just put in new cartridges.

Please refer to this article on how to clean the cartridge nozzles: Blank Pages Printed.

Yes, these machines are designed to only function if all inks are present and meet minimum requirements. Not doing so could result in damage to the print head. The large black ink, the 5, is also a pigment based ink and highly prone to clogging. Letting this machine sit for extended periods of time unused can also cause damage, possibly irreparable, to the print head. We typically recommend people using these style machines always keep a back up set of cartridges on hand to avoid issues.

I had almost the same exact problem. Left the printer unused for a month or so, came back, no black ink being printed, even though the level was still sufficient.
What I did, was boiled a small pot of water, and held the black ink cartridge over the steam, about 3-4 inches above the boiling water, for 2 increments of about a minute. Try not to burn your hand or cook the cartridge lol. I wiped the cartridge head with a piece of paper periodically until I noticed a good bit of dark ink on the paper, then gently wiped the condensation off of the cartridge with a paper towel so as not to put a wet cartridge back in my printer. Put it back in the printer and voila!
Works great so far, although I can't vouch for the long term effects of this solution. I did look at the cartridge a bit later to make sure it wasn't leaking, and it wasn't. You have to steam it the right amount of time. I would guess that the printer cartridge head will inevitably dry out again with limited use. I'm hoping that it will keep working though haha. Hope this helps anyone else with this problem.

Bought a new printer....

I am on my second Photosmart C6180, the first one I had quit printing black ink after 6 months, after hours with the HP help desk, the finally decided to replace the printer. I have now been using the replacement for several months and just this weekend it too quit printing black ink...no copying, no printing and no faxing.  I am now shopping for another, not a HP.  

change your printer cartridge.

note :--do not use refilled cartridges Step 1: Did you just install a new tri-color or photo cartridge? If all three of the following are true, the problem can probably be solved just by letting the printer sit for 30 minutes: You just installed a photo or tri-color print cartridge (the cartridge can be either new or previously-used) The problem appeared right after you installed the cartridge The recently-installed cartridge is the one that is printing the defective patterns on the diagnostic page Sometimes when a tri-color or photo print cartridge is snapped into the print carriage, it ingests a small amount of air, which can prevent some nozzles from working properly. The air soon works its way out of the cartridge. Step 2: Run the clean print cartridges utility If the step above did not solve the problem, clean the print cartridges. Press the Setup button. Use the arrow keys to select Tools and then press the OK button. Select Clean Print Cartridge and then press OK . The device prints a test page. Examine the test page. If the print quality of the page is good, stop here. If the print quality is bad, go on to the next step for further cleaning. Open the Printer Toolbox . There are two ways to do this: Open HP Director , select the Settings menu, then the Print Settings submenu, and finally the Printer Toolbox . If the HP Director method does not work, open Printers and Faxes in the Windows Control Panel , then right-click your printer icon and choose Properties . Click on Printing Preferences . Click the Services tab, then the Service This Device icon. The Printer Toolbox opens. On the Device Services tab, click Clean the Print Cartridges , then follow the on-screen instructions. Up to three levels of cleaning are available. Discard or recycle the page that prints. Step 3: Clean the contacts If the steps have not solved the problem, clean the electrical contacts on the print cartridge and in the carriage in the printer. Gather the following items to clean the cartridge and print carriage: Clean distilled water. Use bottled or filtered water if distilled water is not available. Tap-water can contain contaminants that damage the cartridge. Clean cotton swabs or any soft, lint-free material that will not stick to the cartridges (coffee filters work well) Sheets of paper or a paper towel to rest the cartridges on during cleaning Open the printer cover and wait until the print carriage stops moving. Remove the cartridge and place it on a piece of paper with the nozzle plate facing up. NOTE: Clean the contacts quickly so that the cartridge is not outside of the printer for more than 30 minutes. If the cartridge is outside of the printer for too long, the ink can dry and clog the nozzles. Unplug the printer. Dip a swab in the clean water, and then squeeze it to remove most of the moisture. The swab should be only slightly damp. Clean the print-cartridge contacts. Do not touch the nozzles. Clean the contacts in the print carriage, inside the printer. Either let the cartridge sit for ten minutes to allow the cleaned area to dry, or use a new swab to dry it. Reinstall the cartridge, plug the printer back in, and close the printer cover. Try to print again. If the issue still appears, proceed to the next step. Step 4: Black cartridges only: remove and rest for two hours NOTE: The following procedure does not fix missing lines or streaked bars printed by the tri-color, photo, or gray photo cartridges, or other color-printing problems. Perform the following steps only if the black print cartridge has printed defective patterns or if you notice non-uniform black text-darkness. In the black print cartridge, this problem might be caused by sediments collecting in the nozzle area. Perform the following steps to solve this problem: Remove the black print cartridge. If the carriage has a latch, re-latch it and then close the printer. NOTE: If the printer is not closed, it cannot adequately protect the remaining tri-color cartridge. Place the cartridge on a level surface with the nozzles up (label down). Allow the cartridge to sit undisturbed for two hours. Reinstall the cartridge and print another diagnostic page. Load letter or A4 unused plain white paper into the input tray. Press and hold the Cancel button and then press the Start Copy Color button. Make sure that the test patterns show a complete grid and the thick color lines are complete. More than a few broken lines in a pattern can indicate a problem with the nozzles. You might need to clean the print cartridges. If the black line is missing, faded, streaked, or shows lines, this might indicate a problem with the black print cartridge in the right slot. If any of the color lines are missing, or if the pattern appears faded, streaked, or shows lines, this might indicate a problem with the tri-color print cartridge in the left slot. Look for defects on the page. If the diagnostic page shows no defects for the black cartridge, and if the cartridge was new, align the cartridge. To align the cartridge, follow the steps: Load letter, A4, or legal unused plain white paper into the input tray. In the HP Solution Center, click Settings , point to Print Settings , and then click Printer Toolbox . NOTE: You can also open the Printer Toolbox from the Print Properties dialog box. In the Print Properties dialog box, click the Services tab, and then click Service this device . The Printer Toolbox appears. Click the Device Services tab. Click Align the Print Cartridges and a print cartridge alignment sheet is printed. Load the print cartridge alignment sheet with the print side down on the right front corner of the glass. Press the Start Scan/Reprints button and the HP All-in-One aligns the print cartridges. Recycle or discard the print cartridge alignment sheet. For aligning the cartridges from the hardware only, follow the steps: Load letter or A4 unused plain white paper into the input tray. Press and hold the Cancel button and then the On/Power button. While the Check Paper and Check Print Cartridge lights are blinking, press the following buttons one at a time in the following order: Cancel , Number of Copies , Paper Type , Color Start If the page still shows defects, go to the next step. Step 5: Replace the problem cartridge If the problem has not been solved by the steps above, either the printer or the problem cartridge is defective. If you have not tried cartridge replacement previously to solve this problem, replace the problem cartridge now. Click here to see if your cartridge is covered under warranty (c00059195). If you have already tried cartridge replacement and it did not help, service the printer. Preventing missing lines Missing lines occur when the cartridge nozzles dry out, or when a cartridge is running low on ink. Do not remove the protective tape from a new print cartridge until just before you install it. Once you remove the tape, do not reapply it. After you have removed the protective tape, do not allow anything to touch the nozzles. Print at least once a month to keep the print cartridges in good working order. Always turn the printer off by pressing the button on the printer control panel, rather than by unplugging the printer. Turning the printer off properly allows it to protect the cartridges. If you are removing a cartridge from the printer temporarily (for instance, removing the black cartridge in order to install the photo cartridge), put it in a cartridge protector. If you do not have a cartridge protector and need to remove a cartridge temporarily, put it in an airtight plastic tub. Make sure nothing touches the nozzles. Do not use a plastic bag. If you intend to store print cartridges in a tub for a long period of time, place color cartridges with the nozzles down, and black cartridges with the nozzles up.