India ink, alternatively called Indian ink or Chinese ink, is a simple black ink made of carbon. It has been in use in one form or another since ancient times and became standard for writing and printing in the Western world around the turn of the 20th century. At its most basic, this ink is simply a carbon pigment, such as soot from burnt wood or resin, called lampblack, mixed with water to make a liquid.
Often, India ink contains a binder or adhesive in order to make the final product more durable, and sometimes it also contains perfume. It is sometimes seen in the form of a hard cake or stick that must be moistened before use, and other times as a liquid.
This ink was used in both ancient Egypt and China, where it was originally used on provide contrast on carved hieroglyphics. By the 12th century CE, India ink had become common in Rome. Different shades of black can be achieved with soot from different materials. While a typical early binder in it may have been gelatin, shellac is commonly seen today.
In the early 20th century, India ink became the most popular ink for printing and writing in the West. When made with a shellac binder, it is not ideal for fountain pens, however, as it tends to clog them. Though it is not encountered in everyday life as much as it once was, the ink has a number of specialized uses in the present day. It is a preferred medium for comic strips, for example. It is also the traditional ink used in Chinese and Japanese calligraphy.
India ink is also used in microbiology to prepare slides. It is typically used as a background color, to highlight the bacterium capsule, which remains clear. The bacterial cells are similarly stained with methyl violet, which allows them to show up as a bright purple.