Wicks aren't just for candles. In a general sense, wicks are strips of materials that absorb liquid using capillary action (where liquid flows into a narrow space regardless of external forces such as gravity). In a vape, the wick is the element in the tank that absorbs e-liquid.
Vape cotton is used to create wicks for your vape device. While pre-built coils already include wicking material, making your own rebuildable atomiser coils means you'll need to pick your cotton and install it.
Cotton wicks work by absorbing the e-liquid that is dripped onto the atomiser (in the case of RDA devices) or that is held in the tank (for RTA and RDTA devices). Once the wicking is saturated with e-liquid in the tank, the vape's battery sends power to the coils, heating them up until the heat turns the e-liquid into vapour. This vapour is then inhaled through the drip tip. Meanwhile, more e-liquid absorbs into the wick, ready for your next hit.
The earliest vapes used silica for their wicks instead of cotton, however, most vapers now avoid this material because of health risks. Because silica is made from glass, it can break down into small particles that enter your body when you use your vaping device.
Today, vapes mostly use cotton wicks. While the first cotton wicks used cotton for crafts like knitting, and later wicks were made out of unbleached cotton used in surgeries, we now have purpose-made organic cotton designed for use with vape devices.
Types of cotton for wicks
Loose cotton wicks
One way to buy your vape wick material is as loose cotton which you will need to measure and thread. This is the form that Cotton Bacon and Vapefly Cotton Clouds come in.
Cotton thread wicks
Cotton threads are ready-to-use portions of cotton which are measured to size for use with your vape. Some have aglets on the end like a shoelace. This makes them easier to thread through the coil without any sections of cotton bunching at the ends. If you prefer to use pre-rolled threads rather than loose cotton, check out the Coilology Thread Cotton or the Wotofo Agleted Cotton which is designed for their Profile RDA.