We had two printers here that were giving us issues, which we ran our own test on. The first printer is an Epson Workforce 600 that hasn't been used for over 1.5 years because ink wasn't coming out of majority of the nozzles. We have heard of customers using Windex to clear clogged Epson printers and wanted to test this method (because a lot of other websites stated to NOT use Windex or Rubbing Alcohol to clean printheads). We filled empty refillable cartridges with Windex and put it in the first printer. We ran 3-4 head cleanings 2-3 times for a day, let it sit over the weekend, then repeated the cleanings two days afterward. We inserted cartridges with ink afterward, ran a nozzle check (came out bad), head cleaning, nozzle check (still bad) and another head cleaning. We left the printer alone for 4 hours and ran a couple head cleanings before we left the office. The next following day, we ran one head cleaning and BAM, the printer was printing clean nozzle checks. Keep in mind that the printer was sitting for over 1.5 years of non use, so it took a time and patience for us to get the printer working again without us taking the printer apart.
Our second printer is a Artisan 710, which was giving slightly bad nozzle checks. For this printer, we tried using 2-parts Windex and 1-part 70% rubbing alcohol mixture in some empty refillable cartridges. We ran 5 head cleanings and printed 10+ test pages to flush out the old ink within the printer (this printer has stationary cartridges and an inner ink line that runs to the printhead). Once flushed, we inserted ink cartridges, ran about 5 head cleanings and printed 10+ test pages to get the ink to the printhead. Afterward, we successfully were able to print clean nozzle checks again!
Also remember to do the spike cleaning trick first as this might be the only step needed before proceeding to going to the advanced steps outlined above. Please view the video below to learn how to do this.