Correction fluid is a liquid which can be applied to paper to cover up errors such as those made by a pen or typewriter. The fluid is designed to dry very quickly when exposed to air, allowing people to write or type over it within a minute or so after it is applied.
The earliest versions of correction fluid were developed in the 1950s by founders of Liquid Paper, a popular brand of this product. Another famous brand is Wite-Out®, with many Europeans being familiar with Tipp-Ex. In all cases, it is typically white, reflecting a very common color choice for paper. In addition to correction fluid, people can also purchase correction tape, which works in much the same way.
Before the development of correction fluid, when an error was made, an entire document might have to be discarded if the error could not be covered up or erased. Correction fluid cut down dramatically on waste and headaches for weary secretaries, and it has become a ubiquitous feature in offices as a result. By convention, this fluid is not used on formal correspondence, because some people feel that it looks a bit tacky. If an error is made in an official document, the document will typically be reprinted without the error.
Classically, correction fluid comes in a small bottle with a brush or sponge mounted to the cap to make it easy to use. It can also be found in tubes with nozzles which typically use roller balls to control the flow of the fluid, or in the form of correction pens. Some people prefer to use correction tape because it is neater than a liquid option and it can be written over immediately, and several companies make correction tape in dispensers which are very easy to use for this very reason.
Users often notice that this product thickens over time, sometimes becoming chunky and impossible to use. This is because the solvents which keep the correction fluid in a liquid state slowly evaporate over time, especially if a container is left open, exposing the fluid to the air. One way to prevent the evaporation of the solents is to purchase it in small containers and keep the containers closed when not in use. Incidentally, these same solvents can cause health problems, so it is a good idea to avoid inhaling fumes from correction fluid.