How Printer Ink Works

I've got a question that's deceptively complex. How does printer ink work? You probably haven't thought much about it, but this stuff is a common part of many of our lives. It's everywhere. First, ink and toner are two different things, despite the fact that lots of us use the words interchangeably. Ink is a liquid substance that you apply to a surface like paper. Toner on the other hand, is a solid polymer. It's sort of like a very tiny plastic dust particle substance, and it relies on the physics of electrostatic attraction, pressure and heat.

A general rule of thumb is that you use toner in laser printers and ink in inkjet printers. Inkjet printers shoot ink onto a page through tiny nozzles on a printhead. There can be hundreds or even thousands of nozzles on a single printhead. The HP Office Jet Enterprise X series has forty two thousand two hundred and forty nozzles per printhead. These nozzles are really tiny, about 50 microns wide. That's point zero five millimetres or less than the width of your average human hair.


Welcome the Thermal Bubble Inkjet Printer

Most inkjet printers today are what's known as thermal bubble inkjets, which means they use heat to project ink from the nozzles. The print head has tiny resistors in it, which heat up when you pass an electric current through them. The heat vaporizes the ink. The ink creates a bubble which pushes a tiny amount of ink through the nozzle onto the page. When the bubble pops, it creates a vacuum which pulls more ink into position for the next bubble. This happens at a pretty fast rate. We're talking thirty six thousand times per second with some printers. The ink comes out at high speeds around twenty two miles per hour.

The precision of these nozzles has been described as being equivalent to trying to drop a nickel into a bucket sitting on the ground while you stand on a balcony of a 30 story building. Precision is important because it relates to the resolution you get with the finished printed page measured in DPI or dots per inch. In general, the higher the number, the better the resolution. For all of this to work flawlessly, the ink must be developed with care. A change in formula could cause a drastic effect on printing. Believe it or not, there is an extensive development and testing period for every type of ink and a particular ink design might take five years to perfect.


HP invents the first real inkjet printer

The Inkjet printer first made its debut back in 1984 with the HP thinkJet before printer cartridges were created. Printers used ink soaked ribbons the way typewriters do. Ask your parents about these ribbons. Printer cartridges however have some big advantages over ribbons. They are easier to install, they don't tear or snag the way a ribbon can and the inkjet process using cartridges is much quieter than the old dot matrix printers. The invention of the thermal bubble nozzle was pure luck. An engineer at HP was experimenting with a method to use the thin film technology in integrated circuits while passing electricity through silicon film.

The film overheated and pushed fluid out from under it. The engineer realized that if you could control the movement of fluid, you could create a practical application and from this the idea for the thermal inkjet printer was born. A few years after their debut inkjet printers became the most popular choice for the home consumer. Many of the print heads in the inkjet printers are not in the printer itself. It's actually part of the ink cartridge. By moving the print head to the cartridge they are able to produce less expensive printers. So let's say your ink cartridge runs out of ink. Should you refill it? It's less expensive than buying a new cartridge, but it tends to make cartridges unreliable and can cause quality problems costing you more in the long run.


Saving on Printer Ink costs

It's a better idea to hand your old cartridges over to a recycling program that makes new cartridges from the plastic of older ones. This keeps cartridges out of landfills and also doesn't flood the market with cartridges filled with the wrong type of ink. There are a few ways you can save on ink costs. You can decrease the size of font you use. This is similar to what a student suggested when he claimed the U.S. government could save millions of dollars by switching to Garamond font. But Garamond letters are smaller than other fonts at the same point type. So you might as well use your favorite font and just set the size slightly smaller.

There are more reliable ways to conserve ink. Many printers and programs have an ink saver or draft mode, which uses less ink per printed page. You end up with a lighter printout however you save ink in the process. When you're ready to print a final copy, you can switch the setting and get a darker printout. If you want to save money. Look into a subscription service, which typically has a monthly charge based on the amount of printing you typically need. These services replace empty ink cartridges on demand and spread the cost out over time. It could end up saving you a significant amount of money per year on your printing costs. OK, so that's the story of ink. It's pretty interesting stuff when you get down to it. You might have thought it's as simple as creating a liquid that will stain a paper a certain way. But as it turns out, there's a lot more science and technology behind getting it to work just right. Now if you'll excuse me. I've got some printing to do.


The technical process of ink production

Printing ink is used to print a wide variety of things. Everything from packaging for food, signs and even for home printers. But color is really what sells printing ink. Everything you see that's on a paper like substance has been printed with ink. Most of what we print nowadays uses a process that utilizes a four color system, yellow, magenta, cyan and black. Black is the last color in the ink formula process and that just adds all the highlights and all the detail. Printing ink is composed of two primary things, a pigment, which is the actual color and the vehicle, which is the carrier of the color. The pigment can be anything, a yellow, magenta, cyan, black or any other colours.

The colors start out as a powder and we need to incorporate that into the vehicle, which is really like a sticky, gooey varnish,not unlike honey. Some parts of the "vehicle" are thick and gooey, very sticky, very unlike the finished product. When the process begins the ingredients go into a large pot and then they get put into a mixer. They are heated by mixing until they are much thinner than they would otherwise be at room temperature. It's at this point that the pigment gets added in to the mixture. The pigment itself needs not to be a fine powder so it is ground continuously until it becomes a liquid type substance. The ink needs to be a liquid so it can run through the machines correctly. So the next step is to continue the grinding until this occurs.

The pigments start off as a dry powder and they are initially all stuck together. This needs to be ground down to maximize the reflecting surfaces. You need to break those lumps of pigment apart and to do that, we have two types of machines. The first machine is called a "bead mill". A bead mill has many, many little steel balls in it and they impact on these pigment particles and they break the particles off of this lump. But it gives us a very rough grind. To make the ink smoother so that it can be used you next must run it through three large steel rollers which are running in opposite directions. This imparts a great deal of pressure on the pigment particles and basically smears them apart. It is the best machine for refining the pigments as it imparts the most gloss and the most color strength into the ink.

The next step in making ink is quality control, or QC, as we like to call it. It ensures that the ink is the exact same colour and consistency from batch to batch. The very first test that is done after the ink is run through the bead mill and through the three roll mill is a grind test. You must ensure that every pigment particle has been reduced to its smallest possible size. This ensures a smooth, even print. You want the particles to be capable of producing a shiny and bright print. The most important test done at this stage is the bleach test. This is done by incorporating a small amount of ink into an opaque white substance. This allows us to check the color strength and allows our color computer to see whether the color has been correctly developed. Once a batch is approved by the quality control technician then it is taken to the mixer. At this stage, extra ingredients are added, things like Wax's, which impart rubber assistance and drier's, which allow the ink to turn to a solid film in a relatively short period of time.

Another important QC test that's done is called "tack", this measures how sticky the ink is. You control the tack in the ink to ensure that the printer always gets the same print quality results. The tackiness of the ink determines how the ink performs in the printer. Too much tack will cause printhead clogging and other issues, too little tack may cause leakages and poor quality prints. One of the next things done in the process is to intermix Pantone colors. We need to do this because, again, the color gamut of the yellow magenta cyan and black is not enough to satisfy all of the color variation that are required. By mixing together the base colors of the Pantone you can achieve the full array of colours.

Once this is achieved then in goes back to QC for further testing. Finally the finished product is ran over a three roller mill. This takes out the air and imparts even more gloss and polishing to the ink. The final ink produced should have the best glass, the best running ability, the best set speed, the best rubber resistance. All these terms may sound weird as they are technical terms used in the industry and I won't go into too much depth about these individual characteristics of ink. There you have it, that is how the raw ink product is made.