Your inkjet printer's dirty little secret (1/26/11)

The problem you can see
If you use an inkjet printer, have you ever seen thin horizontal "white lines" in your printouts? This is caused by some of the printer's "jets" getting clogged, which prevents them from spraying their tiny, precisely-formed drops of ink onto the paper. Your printer may even have produced large white areas, which occurs when most or all of its jets get clogged.

What causes clogs?
There are two main causes of clogged ink jets:

The tiny bit of ink at the jet's opening dries up and blocks the nozzle, much like leaving a pen uncapped would dry out the ink at its tip.
Changing ink cartridges introduces air into the print head, and the air bubbles interfere with the flow of ink and can also create dried specks of ink inside the cartridge. (In printers where the print heads and cartridges are a single unit, replacing the ink also replaces the print head, so this particular problem doesn't occur, but the combined cartridge/print heads cost more to replace.)

The solution that you can see
Most inkjet printers have a "cleaning" function you can invoke, either by using the printer software on your computer or by pushing the correct sequence of buttons on the printer's front panel. The cleaning function shoots ink through all of the nozzles in an attempt to moisten and dislodge any clogged ink. Since this doesn't always clear all of the clogs on the first try, you will sometimes have to run the cleaning cycle more than once. Some of the time you may even find that the clogs get worse!

The explanation that you can't see
If you think about the nozzle-cleaning process, you might ask yourself: Where does that waste ink go? Your inkjet printer has a power cord and a parallel or USB data cable, but it doesn't have a waste ink drainpipe, and it doesn't spray that excess ink onto a piece of paper during the cleaning process.

For consumer-level inkjet printers, there seem to be two solutions to this problem:

Some models (including Epson printers) have absorbent pads or sponges in a pan under the print mechanism that collect the waste ink.
Other models (including HP printers) have an open plastic tray (called the "spittoon") where the waste ink collects.

In either design, the waste ink is collected in an internal container that is open to the air, so it will dry out to some degree, but ink sludge will build up over time and eventually overflow or interfere with the printer's ability to function. Don't panic! This will take a number of years. Unfortunately, it is very difficult for the average consumer to take a printer apart and clean out or replace this container.

Some printers try to protect you
In January 2001 I bought a very good inkjet printer, an Epson Stylus Color 860. It still works well today, although in recent years it has developed a minor problem with envelopes. In April 2010 it suddenly stopped printing, and its front panel displayed a pattern (all lights flashing) that was not listed in the user manual. I searched online and eventually found the explanation: My printer's "Protection Counter" had exceeded the recommended level. It turns out that all these years the software inside my printer has kept track of how much waste ink the cleaning function has ever consumed. Like a specialized odometer, this Protection Counter is the printer's way of predicting when its overflow ink pads may be near their capacity. When I learned how complicated it was just to get inside the printer and get access to the pads, I decided it wasn't worth the time and effort. I also found a little program that reset my printer's Protection Counter back to 0, so I can print once again, but I've also put some paper towels under it to catch the inevitable ink spill from the overflow pad.

Older printers may give you an unwelcome surprise
In 2009, a client of mine bought a new computer, which also came with a free printer. Her old Epson Stylus C40UX inkjet printer was still working fine, but since she didn't need two printers she gave the older one to me to find it a good home. I brought it back to my house, but in the course of carrying it to and from my car, I wasn't careful to keep it level at all times. She had been using that printer long before I started working with her in 2005, so it was probably at least 5 years old. As you can imagine, some ink started to drip out from one end of the printer, most likely from the overflow ink pads. It was far too much work to try to open it up and clean the mess, so I brought it to a local electronics recycling place.

Where to go from here

When your inkjet printer develops clogged jets, I recommend using the cleaning function to clear its nozzles no more than three times before switching to replacing the corresponding ink cartridges, so you don't waste more ink than necessary.
If your inkjet printer is more than 5 or 6 years old, I recommend putting some paper towels under it in case its waste ink collection tray overflows. Also, be careful when moving an old printer, as you may tilt it and spill the ink in its overflow tray, which can create a surprising mess.
See http://en.wikipedia.org/wiki/Inkjet_spittoon for some photos of an HP inkjet spittoon.
If your printer no longer works, rather than throwing it in the trash, consider recycling it. Many towns have local electronics recycling programs, and many printer manufacturers will recycle it for you as well. For example, if you go to http://www.epson.com or http://www.hp.com and type "recycle" into the Search box, you'll find that Epson and Hewlett-Packard offer many recycling options.

If you're confused or frustrated by something on your computer, I like to say, "You can do it!" You might just need a little encouragement, or information, or change of perspective, and that's where I come in.

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