View of the nozzles on a thermal bubble inkjet print head

 

Thermal bubble - Used by manufacturers such as Canon and Hewlett Packard, this method is commonly referred to as bubble jet. In a thermal inkjet printer, tiny resistors create heat, and this heat vaporizes ink to create a bubble. As the bubble expands, some of the ink is pushed out of a nozzle onto the paper. When the bubble "pops" (collapses), a vacuum is created. This pulls more ink into the print head from the cartridge. A typical bubble jet print head has 300 or 600 tiny nozzles, and all of them can fire a droplet simultaneously. Click the button to see how a thermal bubble inkjet printer works.

Piezoelectric Used by Epson, this technology uses piezo crystals. A crystal is located at the back of the ink reservoir of each nozzle. The crystal receives a tiny electric charge that causes it to vibrate. When the crystal vibrates inward, it forces a tiny amount of ink out of the nozzle. When it vibrates out, it pulls some more ink into the reservoir to replace the ink sprayed out.

Click on the button to see how a piezoelectric inkjet printer works.

Let's walk through the printing process to see just what happens.

Paper and Ink
Inkjet printers are fairly inexpensive. They cost less than a typical black-and-white laser printer, and much less than a color laser printer. In fact, quite a few of the manufacturers sell some of their printers at a loss. Quite often, you can find the printer on sale for less than you would pay for a set of the ink cartridges!

 

This printer sells for less than $100.

Why would they do this? Because they count on the supplies you purchase to provide their profit. This is very similar to the way the video game business works. The hardware is sold at or below cost. Once you buy a particular brand of hardware, then you must buy the other products that work with that hardware. In other words, you can't buy a printer from Manufacturer A and ink cartridges from Manufacturer B. They will not work together.

 

A typical color ink cartridge: This cartridge has cyan, magenta and yellow inks in separate reservoirs.

Another way that they have reduced costs is by incorporating much of the actual print head into the cartridge itself. The manufacturers believe that since the print head is the part of the printer that is most likely to wear out, replacing it every time you replace the cartridge increases the life of the printer.

The paper you use on an inkjet printer greatly determines the quality of the image. Standard copier paper works, but doesn't provide as crisp and bright an image as paper made for an inkjet printer. There are two main factors that affect image quality:

 

	Brightness
	Absorption

The brightness of a paper is normally determined by how rough the surface of the paper is. A course or rough paper will scatter light in several directions, whereas a smooth paper will reflect more of the light back in the same direction. This makes the paper appear brighter, which in turn makes any image on the paper appear brighter. You can see this yourself by comparing a photo in a newspaper with a photo in a magazine. The smooth paper of the magazine page reflects light back to your eye much better than the rough texture of the newspaper. Any paper that is listed as being bright is generally a smoother-than-normal paper.

The other key factor in image quality is absorption. When the ink is sprayed onto the paper, it should stay in a tight, symmetrical dot. The ink should not be absorbed too much into the paper. If that happens, the dot will begin to feather. This means that it will spread out in an irregular fashion to cover a slightly larger area than the printer expects it to. The result is an page that looks somewhat fuzzy, particularly at the edges of objects and text.

 

Imagine that the dot on the left is on coated paper and the dot on the right is on low-grade copier paper. Notice how irregular and larger the right dot is compared to the left one.

As stated, feathering is caused by the paper absorbing the ink. To combat this, high-quality inkjet paper is coated with a waxy film that keeps the ink on the surface of the paper. Coated paper normally yields a dramatically better print than other paper. The low absorption of coated paper is key to the high resolution capabilities of many of today's inkjet printers. For example, a typical Epson inkjet printer can print at a resolution of up to 720x720 dpi on standard paper. With coated paper, the resolution increases to 1440x720 dpi. The reason is that the printer can actually shift the paper slightly and add a second row of dots for every normal row, knowing that the image will not feather and cause the dots to blur together.

Inkjet printers are capable of printing on a variety of media. Commercial inkjet printers sometimes spray directly on an item like the label on a beer bottle. For consumer use, there are a number of specialty papers, ranging from adhesive-backed labels or stickers to business cards and brochures. You can even get iron-on transfers that allow you to create an image and put it on a T-shirt! One thing is for certain, inkjet printers definitely provide an easy and affordable way to unleash your creativity.