The use, misuse, and re-use of the laser printer toner cartridge is a confusing subject in many ways. Can it be refilled? Is it safe to use a refilled cartridge? All good questions. And most with simple answers if you take a few minutes to examine the issues.
First of all, why would anyone consider refilling a toner cartridge? Primarily to save money. A new toner cartridge for a laser printer costs about $100 retail, give or take a little. They are rated at about 3,000-3,500 pages worth of output, which varies according to the coverage per page (pages with more white space use less toner).
Canon engine cartridges are about the most common among the cartridge type lasers, since many of the laser printers common to desktop publishing, such as the Apple LaserWriter line, the QMS 800's, the original H-P Laser Jet, and many others, are all based on the Canon engine line. One thing that this means is that you can use an Apple LaserWriter cartridge in a Hewlett-Packard printer, or vice versa.
Once the toner is gone, you are supposed to pack the old cartridge up, and ship it back to the manufacturer for proper disposal, since some components in the cartridge, such as the drum, are considered to be a low level hazardous waste, and cannot be thrown out with the regular trash. Depending on who you ask about that particular point, answers vary considerably. One thing that is important is that you shouldn't get the impression that your toner cartridge is dangerous to handle. Just that the EPA would like this sort of material disposed of properly.
In the additional benefits category, is the consistency and quality of solid image areas on your printed page. One thing that most every owner of a laser printer knows is that the quality of large areas of solid blocks often leaves something to be desired. Some solids have streaks, or vary considerably in consistency from end to end. Many factors contribute to this problem, such as the moisture content in a sheet of paper at the time you are printing on it, the quality of the paper, and so on. But the biggest factor is the drum of the toner cartridge and the toner itself. If the drum is well broken in, and the toner is good, most likely you have minimal or no problems with your solids. If the drum isn't broken in, you definitely have a problem. And if the toner cartridge has been sitting around in a humid environment, you have even more problems.
A great deal of disagreement exists on just how many copies it takes to properly break in a drum on a toner cartridge, and how many copies it's good for. It has been noted that with some new cartridges, you can never get them to break in properly. On others, 400-500 pages will get you to the point where they consistently produce good images. For the most part, they all begin to reach their optimum performance at 2,500-3,000 pages. That's not far from when you run out of toner. So just about the time that you start to get good performance, the toner runs out. There in lies the rationale behind the biggest benefit of refills: quality of printed images. With a well broken in drum, and good toner, you can expect to get a minimum of problems with the quality of solid areas on the printed page, and you can expect consistency.
How many refills is a cartridge (or more particularly, the drum) good for? To some extent it depends on the usage. Was it used for more graphically intense work, or mostly type, since it was last filled? Some toner cartridges can be refilled three to four times or more, depending on the use and care of the toner cartridge. In conclusion, toner cartridge refills, when properly done, are safe for use in your printer, cost less than buying a new one. Not only do you help protect the environment when you use reconditioned cartridges but the quality of your output actually improves.