How to wick a coil for an RTA, RDA or MTL tank

The same wicking technique gives a perfect build in a dripper and a leak in a tank. The reason lies in the atomiser more than the cotton, because an RTA, an RDA and a tight-draw tank don’t feed the wick in the same way. Knowing how to wick a coil starts with knowing where the liquid is waiting for the wick, and how quickly it needs to reach it.

How to wick a coil, the common rule and what changes

How to wick a coil? Three moves apply everywhere. The wick is about twice the coil’s inner diameter wide, it slides through with light resistance without bending the wraps, and its tails are fluffed with tweezers before they go into place. What changes from one atomiser to the next is the length of the tails and where they sit.

These notes draw on three published guides, from the French retailers Arômes et Liquides and Taklope, the latter for tight-draw tanks, and from the vaping site Vapebeat, alongside the workshop’s own calculations.

Atomiser	Wick width	Tail length	Placement
RTA, tank	2 × inner diameter	Down to the juice ports	Laid over the ports, never packed
RDA, dripper	2 × inner diameter	Level with the deck	In the well, well fluffed
MTL, tight draw	4 to 6 mm for a 2 to 3 mm coil	Depends on the shape of the wells	Thinned, never stuffed

Cutting the wick to the coil’s diameter

The twice-the-inner-diameter rule gives a strip of 6 mm for a 3 mm coil, 5 mm for 2.5 mm and 4 mm for 2 mm. Leave plenty of length, as taking cotton away is easier than starting again.

Ready-made laces are calibrated for a given diameter, so wicks meant for 3 mm coils need thinning to go through a 2.5 mm coil. The method is to thread the lace in, pull gently on the end while teasing out a few fibres with the other hand, and repeat until the wick slides.

You feel the right fit by pulling the wick left and right. If it slips out with no effort, there isn’t enough cotton. If the coil twists off-centre, there is too much. When it is right, it slides with light resistance and the cotton bulges slightly on each side of the wraps.

How to wick a coil in an RTA

In a tank, knowing how to wick a coil comes down to setting a valve. The tails have to let liquid in fast enough to feed the coil, without opening a direct path to the air inlets.

Covering the juice ports without blocking them

Trim the tails so they cover the juice ports on the deck. They should sit over the ports rather than drop inside them, and cover them completely, otherwise the tank leaks or spits liquid.

Then fluff each tail with bent tweezers and lay it in without folding or packing it. Compressed cotton slows the flow of liquid just as much as a tail that is too short lets it rush through.

Single and dual coils

With a single coil, one wick feeds both sides of the deck. With a dual build, each coil has its own wick, and all four tails need the same length and density, otherwise one coil drinks faster than the other. The deck of the Bonza Pro RTA, covered in our build notes, with its single and dual chambers, shows the symmetry to respect.

Wicking a dripper, where the cotton is the reservoir

An RDA has no tank. Liquid is dripped straight onto the wick, which holds it in its tails and in the well of the deck.

Trim the tails level with the deck, then fluff them so they hold as much liquid as possible without overflowing. Leave some space between the bottom of the coil and the air holes, so the air flows evenly around the wraps.

The dripper tells you itself when cotton is short. A coil that pops and crackles usually has too little cotton, or too much liquid dropped on at once. In the first case you rewick slightly thicker, in the second you drip more lightly.

Wicking a tight-draw MTL tank

Tight-draw tanks work with small coils, generally between 2 and 3 mm inner diameter, which brings the wick down to 4 to 6 mm wide. On a 2.5 mm coil in 0.32 mm wire, seven wraps give 1.12 Ω, and the wick narrows to 5 mm.

The shape of the wells then sets the tail length. With channels open to the bottom of the tank, you can leave a good length of wick. In closed, narrow wells, you have to cut short and thin the ends so they aren’t stuffed in. Some closed but wide wells, on the other hand, need plenty of cotton or they leak.

This is where your eye counts most. Look at your wells before you cut, and always leave a little margin, since a tail that is too long can be shortened while one that is too short means starting over.

Leaks, crackling or a burnt taste, fixing the wick

Many faults on a fresh build come down to the cotton, and each one has its signature. The table gathers the causes described by the guides mentioned above.

Symptom	Likely cause	Fix
Leaking or gurgling in an RTA	Tails too short or too thin	Rewick with longer or thicker tails
Repeated burnt taste	Wick too thick or packed into the wells	Shorten or thin the tails
Crackling in a dripper	Too little cotton, or too much liquid at once	Thicker wick, lighter drips

After every rewick, take a fresh ohm reading. As it slides through, the wick can push the wraps against the deck, and the value should stay where it was, within the range your mod and batteries accept.

FAQ

Five detailed questions that come up often, and that the sections above don’t cover.

Pre-made laces or strips cut to size, which should you use?

For a first attempt, laces make life easier, with a stiff tip that threads into the coil. Strips take an extra snip of the scissors but let you match the width exactly to the coil’s diameter.

Should you dry fire the coil before rewicking?

Yes for a wire such as kanthal, once the old cotton is out. A few dry pulses burn off the deposit left by the liquid. Then let the coil cool completely before threading the new wick.

How much liquid to prime fresh cotton?

Enough for the wick to look translucent or tinted across its whole surface. Work in several passes, one side then the other, to give the fibres time to soak it up deeply.

Should you close the airflow before filling an RTA?

Yes, that is the usual precaution before filling an RTA, especially when the air comes in from the base of the deck. Open the airflow back to your usual setting afterwards.

Why cut off the scrunched-up end of the cotton?

The end you rolled to thread it through the coil is denser than the rest of the wick. Left in place, it can slow the flow of liquid on that side, hence the habit of always trimming it before placing the tails.

How to wick a coil, a question of atomiser first and foremost

The basic rule fits in one sentence, a wick twice the inner diameter wide that slides through with light resistance. Everything else depends on the atomiser. Knowing how to wick a coil means matching the length and placement of the tails to the RTA, the dripper or the MTL tank on your bench.

A good wick shows itself quickly, with no leaks, no crackling and no burnt taste. You will redo it often, and that is no bad thing, since every rewick sharpens the technique.

Also on the bench

Build notes from L’Atelier Brouillard, for adult readers only. Vaping products usually contain nicotine, which is addictive, and nicotine vaping products are not for sale to under-18s in the UK. Nothing here is a recommendation to buy.