How can you print without ink?


Most printing today relies on ink, but there are many inkless options.
Most printing today relies on ink, but there are many inkless options.
Bob Peterson/UpperCut Images/Getty Images

In an increasingly paperless world, you'd guess printing would become obsolete. But that's not the case. Because reading computer screens strains people's eyes and they'd prefer to hold a book or newspaper in their hands, printing technology remains indispensible. Ink on the other hand, we could do without.

Let's face it -- ink is messy, expensive and high-maintenance. Wouldn't it be nice to eliminate it? Some old and new technologies provide the opportunity to do just that. Of course, whether a process is truly "inkless" depends on what your definition of "ink" is.

Generally, true ink consists of a dye or pigment, which can be organic or inorganic, in a liquid. A dye is a colored substance that dissolves in a liquid solvent, while a pigment consists of very fine, sometimes powdery, colored particles that don't dissolve, but rather are suspended in a liquid. The solvents and liquid that hold the dye or pigment can be water, or even oils or alcohols [source: Evans].

Many methods, both ancient and cutting edge, allow us to forego ink. The old methods of printing, such as engraving, don't involve anything like ink. Engraving uses a tool to imprint or carve words or images on a hard surface. However, as impressive as it looks on special plaques, engraving obviously can't be used on common paper, so it's an impractical, difficult and expensive process. Another inkless printing technique, hot foil printing, applies foil to a surface by applying heat and pressure. While the text looks attractive, this method is also impractical for mass production.

But newer technology is allowing us to print conveniently and cheaply without a drop of ink. What are these cutting-edge inkless printing methods? Keep reading to find out. 

Modern Inkless Printing Methods

Zink paper uses embedded dye crystals that react to heat to print an image.
Zink paper uses embedded dye crystals that react to heat to print an image.
iStockPhoto/John Black

Technology seems to have come full circle since the invention of ink some 4,000 years ago. Although the printing press, an efficient way to apply ink to paper on a mass scale, was one of the most important technological advances in the history of humanity, taking ink out of the equation can simplify modern printers.

Take, for instance, the thermal fax machine. This useful gadget merely needs to apply heat to special thermal paper to print text or images. Without the mechanisms that ink requires, the printer is simpler, more durable, cheaper to maintain and takes up less space than ink printers. A different type of thermal fax machine uses ribbon rather than ink and melts the ribbon to paper to print text. Read How Thermal Fax Machines Work to learn more about this process.

Conventional photocopiers actually don't technically use ink either. If you've ever maintained a photocopier or read How Photocopiers Work, you know that they use a dry, powdery material called toner. The toner is negatively charged, and the copier uses static electricity to print copies. The copier uses light to measure the print on the original and assembles the powdery toner to fall to positively charged areas to replicate the text or image. It then fuses the toner to another piece of paper to make a copy.

Thermal fax machines and photocopiers are far from cutting edge and haven't come close to replacing ink. Despite their availability, people still prefer the sharp look and durable quality that ink printers produce. Nevertheless, scientists are now developing several other fascinating printing processes that might give ink a run for its money.

One company, Zink (which stands for zero ink), announced in 2007 that it has perfected a technology for printing without ink. Using embedded dye crystals in the paper, a printer merely needs to apply the right amount of heat to bring those crystals alive and produce a quality print -- even photos. Because there's no need for ink, this special paper allows printers to be exceptionally small. For its debut, Zink partnered with Polaroid, the company that pioneered instant film, to make an ink-free instant mobile photo printer, which isn't much bigger than a pack of cards.

Xerox, the company with the name that's synonymous with photocopiers, is also developing an inkless printing method. But the process it's working on is radically different from predecessors. Inkless prints aren't known for their long-lasting durability, but Xerox is turning this drawback into an asset. In fact, they're intentionally working to make inkless prints easily erasable. Although this seems counterintuitive, it makes a lot of sense for several reasons.

Xerox is developing an inkless, erasable printing method. Prototypes of the reusable paper gradually fade after a day.
Xerox Corporation

In offices, many people print papers to use for just a day or even less. To make this practice more economical and environmentally friendly, Xerox is developing paper that doesn't require ink and is completely reusable. It works this way: Xerox first coats paper in heliochromic chemicals. These chemicals darken when the paper is exposed to ultraviolet light (UV). They're similar to the chemicals that cause certain sunglasses to darken in the sunlight and gradually lighten again in dim light. The printer, then, merely "prints" by zapping the paper with the right wavelength of UV light and in the right places. The print can be used and then immediately erased by applying another wavelength of light. With prototypes of this technology, the print automatically fades 16 to 24 hours after printing. But Xerox is working to extend this time period. Ideally, the text will last until the user is ready to erase it manually.

Want to learn more about printing technology? Explore the links on the next page.

Related HowStuffWorks Articles

More Great Links

Sources

  • Evans, Steve. "Mixture of dyes, pigment, liquids makes world more colorful." Cornell Center for Materials Research." July 12, 2006. (June 13, 2008) http://www.ccmr.cornell.edu/education/ask/index.html?quid=1068
  • Genuth, Iddo. "Xerox Inkless Printer." The Future of Things. February 15, 2007. (June 13, 2008). http://www.tfot.info/articles.php?itemId=50/58/