Structure and effect
The wick consists of many intertwined fibers that represent fine channels and use capillary forces to feed liquid fuel (e.g. oil , petroleum , denatured alcohol , wax ) into the flame against the force of gravity . This is why capillary action is sometimes referred to as the wicking effect . The wick improves the gasification of the liquid. This locally increases the vapor pressure and lowers the flash point of the liquid so that an ignitable mixture is created.
Generally, a wick is thread-shaped. But flat materials can also support combustion in a similar way to a wick. For example, oil cannot be ignited with a match , while an oil-soaked cotton rag easily catches fire.
As a rule, wicks are made of cotton or a glass fiber braid , the latter being characterized by the fact that they do not burn themselves. In ancient times and in the Middle Ages , other materials were used, such. B. Asbestos wicks .
Wicks from tallow candles, which made up the majority of candles until the beginning of the 19th century, have to be regularly shortened ("blown") when they burn down, because the longer the wick length, the larger the flame, which leads to strong soot formation and rapid melting of the fuel . For this “ cleaning of the lights” special wick scissors are used, with which the sniff is caught after it has been cut off.
Today's wicks are braided asymmetrically so that they curve to the side in the flame. The area cranked out of the flame burns completely in the air and does not have to be cut off.