Ok so maybe the title of this article is a bit misleading but really it was meant to attract you the reader to this article. Of course there is some sort of ink or chemical needed for any printing but what the title really wanted to say was printing without you having to use ink.
Printing is a very old technology. Over the many years that human being knew how to print the printing technology has advanced significantly. At first printing was very slow and only black and white. Printing was limited in resolution and was really used just to print short text messages. Later on the process has been improved allowing faster printing of complete books and eventually it improved all the way to today color super fast printing machines.
What has not changed for many years is the fact that printing requires some sort of ink. The definition of ink can be broadened to basically include any perishable substance that is used in the process of printing with the purpose of creating the printed dots on the print object being paper or any other object. When using the word ink most people think about black dirty material that usually ends up spilled on your hands or that one white shirt that you now need to take to the dry cleaners.
But in the modern era ink can actually take the shape of high tech relatively clean material. For example inkjet printers use ink cartridges that include special material as ink. That special ink is a high technology material that is electrically charged and then accurately placed on the paper using a high tech printing head that uses electricity to release the exact amount of ink at the exact time. Holding an ink cartridge is completely safe and clean. There are no spills and it is not dirty. In fact it is hard to get ink out of the cartridge without the electronic circuitry that the printer uses in conjunction with the cartridge. The tiny holes from which the electrically charged ink leaves the cartridge are too small for any ink to be released without the proper electrical charge.
Yet another form of ink is chemicals that are pre coated on the printing paper. Although this might not seem like ink it is really ink that is utilized in a reverse order. Instead of the printer placing ink on paper the paper is pre coated with ink and then the printer manipulates that ink in order to create the effects needed. Such process is most common when printing digital photos on digital photo paper. Such ink is very clean too. Touching a photo paper would not stain your hands or your clothes. When put in a printer the photo paper is heated up changing the ink qualities and making it ready for the brightness and color transformations needed for the specific print. As can be seen ink can come in many forms and shapes. From the old dirty ink to modern super clean high technology ink cartridges used by modern fast printers.
Danette Mckay explains about this subject in more depth at digital photo printing