# How to wick a coil without deforming it > How to wick a coil properly: cotton density, tail length, and the mistakes behind dry hits and leaks. The gesture explained step by step. The coil is clean, the reading on the mod makes sense, everything looks right. Then the cotton goes in, and the same immaculate build produces a burnt taste within three puffs, or starts weeping liquid out of the airflow holes. In the vast majority of cases the coil is not the problem. Learning **how to wick a coil** is what separates a build that works from one that misbehaves, and it comes down to density and placement rather than skill. ## How to wick a coil, in one sentence Wicking means threading a length of cotton through the coil that is just thick enough to offer slight friction as it passes, without ever pulling the turns out of shape, then trimming and placing the tails so liquid reaches the wick without being squeezed out of it. The whole difficulty sits in the word slight. Too dense and the cotton starves; too loose and liquid runs straight through. The two failures have opposite symptoms, and both are easy to read once you know what they look like. ## The density test: how to wick a coil by feel There is no universal measurement in millimetres, because the right volume depends on the internal diameter of your own coil. The reference is tactile instead, and it is reliable. If you use too much cotton, the tension starts to distort the coil and pull it out of position. If you use too little, the wick slides through without meeting any resistance at all. The correct amount passes through with slight friction and leaves the turns exactly where they were. That feel is learned in three or four builds, not in one. The rule while you are learning is simple: if you have to push hard, there is too much cotton. Remove fibres from the length rather than forcing the strand. ## Preparing the wick before it goes anywhere near the coil Cotton shoved into a coil damages the build before the first puff. Preparation takes ten seconds and prevents most of the damage. Pinch one end of the strand between two fingers and roll it into a tapered point. That point acts as a guide: it threads through the coil and pulls the rest of the cotton behind it. This is the only moment when your fingers should touch the wick, so wash your hands before starting. If the wick jams, it is too thick. Pull it back out, thin it along the length and try again. Pushing harder only displaces the coil, which may then come into contact with a metal part of the deck. A coil moved by wicking has to be repositioned and re-checked on the mod before use, because contact with the cap or the deck creates a [short circuit](/uk/vape-short-circuit/) that you cannot see from the outside. ## Trimming and placing the tails Once the wick is through, two tails hang out either side. Their length and their position determine capillary action, which is the speed at which liquid climbs back towards the coil. This is where dripper logic and tank logic diverge, and where generic tutorials tend to give one answer for two different problems. On an open dripper deck, trim the tails and then tuck them down into the juice well, roughly until they reach the floor of the deck. The cotton sits in the reservoir it feeds, so contact with the well is what keeps it supplied. On a tank style atomiser the objective changes. The aim is to fill the wick ports completely, without packing the cotton and without leaving large voids. Ports that are half empty let liquid past; ports crammed tight stop it moving at all. That single distinction explains a good share of the leaks people report on rebuildable tanks, and it is the reason a tank build such as a [Geekvape Zeus](/uk/geekvape-zeus/) RTA rewards a careful hand more than a dripper does. ## Reading the symptom: too much or not enough The good news is that the device tells you what is wrong. You only have to translate. A dry, acrid taste in the first few puffs, usually called a dry hit, means the cotton is not being supplied fast enough: the wick is too dense, or the tails are badly placed. A liquid that creeps up into the drip tip or seeps out of the airflow means the opposite, an excess of flow through wicking that is too thin or ports that are underfilled. A moderate crackle is neither of those. It is the normal sound of liquid vaporising against the coil, and chasing it away usually means overpacking the wick. The adjustment is always made by removing fibres, never by adding them. Cotton that has been compressed to fit was too much cotton in the first place, and it will keep starving no matter how much liquid you drop onto it. ## Priming, then rewicking without wrecking the build New cotton is dry, and dry cotton heated with no liquid in it burns instantly. Priming means dripping liquid directly onto the wick and the coil until it is visibly saturated, then leaving it a few minutes before the first puff. On a tank, filling and waiting does the same job through the ports. Rewicking follows the same protocol as the first wicking, with one difference: the coil stays where it is. Pull the old cotton out from one side without dragging on the turns, dry clean the coil, then thread the new strand through. A coil in good condition takes several cotton changes before it is worth rebuilding, which is a large part of why rebuildables appeal in the first place. Manufacturers acknowledge this quietly. Several rebuildable tanks ship with spare cotton alongside the assembly tools, which is a way of admitting that knowing **how to wick a coil** is part of owning the device rather than an optional extra you might buy later. Careful wicking cuts down incidents noticeably, but it does not replace the checks described in our guide to the [vape coil build](/uk/vape-coil-build/). Those remain the only real safety barrier, and they need repeating after every manipulation, wicking included, because a coil that has been nudged out of place reads differently on the mod. ## Frequently asked questions ### What cotton should be used for a vape build? Cotton sold for vaping, unbleached and untreated, either as pre-cut laces or as a pad you cut yourself. Cosmetic cotton wool from a chemist is not intended for this use and may contain processing agents. ### How often does the cotton need changing? As soon as the taste degrades or darkens, which happens faster with sweetened liquids and at higher output. No fixed interval applies: the indicator is taste, not time. ### Can cotton be washed instead of replaced? No. Saturated cotton does not rinse usefully. It is replaced, which costs very little per build and takes a couple of minutes. ### Should cotton be soaked before insertion? No. It goes in dry and is primed once in place. Wet cotton compresses and becomes almost impossible to thread cleanly through the coil. ### Can cotton cause an unusual resistance reading? Not directly, since cotton does not conduct. But wicking that shifts the coil can create contact and change what the mod displays, which is exactly why you re-check the reading after every wicking. ## Wicking is the gesture that decides the rest A successful build rarely comes down to a beautiful coil, and almost always to the cotton. Getting the density right, then placing the tails according to the type of atomiser, resolves most of the taste and leak problems people meet in their first weeks with a rebuildable. It is also the most repeated gesture in the whole hobby, the one you will do dozens of times more often than you will wind wire. Learning **how to wick a coil** properly on the first build saves you from unlearning a bad habit on the twentieth, and it costs nothing but a little patience with the first few strands. Editorial content for adult readers only. Vaping products contain nicotine, a substance that causes addiction. Not for sale to under-18s in the United Kingdom. This article is not a buying recommendation.