They say that choosing a coil for your device is a task that can't be resolved without preparation. That you need to keep in mind the various types of builds, materials and parameters. Let's figure out if that's true.
In fact, only a few variables warrant real attention, and if for some reason you don't like your coil, it can always be quickly changed.
A coil is a metal spiral that is used to evaporate liquid. The coil's specs affect wattage, amount of flavor and vapor, as well as liquid and charge consumption rate.
Both simple single wire coils and complex multi-strand structures from the realm of coil porn are used.
What to focus on?
When it comes to coils, the key parameter is resistance. Resistance depends on the material used, the number of wraps, the post diameter (the base onto which the coil is wound) and the thickness of the wire.
The lower the resistance, the higher the wattage that your coil will require. For example, a resistance of 1 Ohm would necessitate about 12 watts of power, and around 40 watts for 0,3 Ohm. Comfortable wattage will also depend on the size of your coil. A big fat coil is harder to heat up, so you'll need to turn up the power in order to quick start it.
To perform calculations for simple coils, use a coil calculator. It's easy to find using any search engine.
Kanthal or fecral. The most popular coil building material. Consists of iron, chromium and aluminium. Easy and inexpensive in practice. Doesn't change its resistance when heated.
Nichrome. An alloy of nickel and chromium. Has a slightly lower resistance than that of kanthal, but is more durable.
Nickel. A fussy metal with a very low internal resistance. Can release toxic substances upon strong heating. It used to be used in temperature control mode, and is now considered obsolete.
Titanium. A safe replacement for nickel. Titanium is expensive and has its quirks. Just like nickel, used in temperature control mode in the past.
Stainless steel. A convenient and inexpensive material. Has a low internal resistance, which allows the coils to be powerful and durable. It's the only material that is convenient for both temperature control and wattage tweaking.
Silica. The ancestor of modern wicks. Almost no one ever uses it anymore. Everyone has switched over to cotton.
Cotton wool. The most popular material thanks to the fact that it absorbs liquid well and lasts long enough. Pharmacy-bought cotton gives off a strong aftertaste, that's why specially prepared Japanese cotton is used.
Linen. A relatively new trend. Absorbs better, lasts longer, delivers great flavor. Rewicking it can pose a challenge, though.
Stainless steel mesh. Not very common due to difficult installation and start-up. Used in special tanks. Despite the disadvantages, the mesh is durable and provides a bright, clean flavor.
For the wick to be evenly heated, the coil wraps need to stick together tightly.
In chip-based mods, the resistance of a finished build has to be higher than 0.1 Ohm. Some mods might not be able to "read" such a coil and can malfunction.
The coil must not touch the walls of the heating chamber, and must be tightly fixed in the posts. Modern tanks and RDAs are designed for all kinds of setups, but older devices need more attention in this regard.
Now that you know all the basics, we can move on to various types of coils. High wattages, clouds of vapor and large coils lie ahead, but first — a cheat sheet.
The most important parameter of a coil is its resistance. The lower it is, the higher the wattage will be. Kanthal and Japanese cotton wick make up an easy-to-use coil for beginners.