Pull a worn-out coil from your tank and you will often find a black, sticky crust across the top of it. Vapers call that coil gunk. It is a different problem from a burnt wick, it has a handful of well-understood causes, and a few changes in what and how you vape can slow it down. This article explains what the gunk is, separates it from a burnt coil, and then goes through the main causes one at a time.
What coil gunk is
Gunk is residue left behind by e-liquid. Each time the coil heats, a little sticky material stays on it, and the layers build up over time. As the deposit grows it turns darker and thicker until the clean flavor of the juice no longer comes through. What you get instead is a dull, burnt note with only a trace of the original flavor behind it.
High-wattage tanks that put out large clouds build residue faster, and sweet juices faster still. You can clean a gunked coil, and we explain how in our coil cleaning guide, but at best that usually buys a few extra days before a fresh coil has to go in.
Gunk is not the same as a burnt coil
Residue building up until a coil is unusable is one thing. Scorching the cotton is another, and it happens in two common ways:
- pressing the fire button when you are not inhaling
- taking a long pull after the tank has run dry
A burnt coil cannot be rescued unless you re-wick it yourself with fresh vaping cotton. For most people it is less trouble simply to fit a new one.
Sweetened juice
Sweetener makes e-liquid taste better and is also the quickest route to a dead coil. Sweeteners such as sucralose caramelize when heated and leave a deposit behind. Thick dessert flavors like custard, sugary sour and chewy candy juices, and rich fruit flavors such as blueberry and strawberry tend to clog coils sooner than others. With juices like these a coil is typically finished after 2-3 weeks, even if the odd good hit still comes through.
Vaping juice with little or no sweetener avoids the problem, though most vapers want a sweet liquid and find unsweetened ones bland. A few vendors do sell unsweetened e-juice, mostly smaller independent companies, and it takes some searching to find them. Their bottles may cost more, since the popular lines are produced in large volumes, but you spend less on replacement coils, and you may come across flavor profiles you would not otherwise have tried. One more thing to know: plain menthol vape juice contains no sweetener, although flavored menthol blends can.
High wattage and chain vaping
Higher wattage means more heat on the cotton. With a large tank (the TFV12 is one example) run at 100W+, taking hit after hit without a break, known as chain-vaping, risks overworking and burning the coil.
People chain vape for two main reasons. Sometimes the flavor is simply good enough that you keep reaching for it, in which case the fix is to slow down and leave time between puffs. Other times the puffs are about nicotine. For that case the original article pointed to nicotine strength: nicotine salts carry a high nicotine content with a smoother taste (see our nic salt article), and freebase liquids are sold in strengths of 6mg, 12mg and in some cases 24mg. Be aware that high-strength liquid in a large, powerful tank can produce a throat hit that is too harsh to tolerate, so a stronger juice belongs with a low-powered tank. That pairing of lower wattage and fewer puffs is what may lengthen the life of a coil. Nicotine is addictive, whatever the strength.
Max VG and darker liquids
Max VG juice gives a smoother throat hit and bigger clouds, and it also uses up coils more quickly than the usual VG/PG blends of 70/30, 60/40 or 50/50. Our guide to VG and PG covers the difference between the two.
Color matters as well. Liquids that are not fully clear can clog a coil. Juice containing nicotine usually has a yellow tint, anywhere from barely visible to the shade of vegetable oil or darker, and the more yellow the liquid, the more likely it is to leave buildup. One company, Juice Hog, sold a red e-juice that became known for staining coils red and leaving its flavor behind even after the juice was changed and the tank rinsed out. Residue has many causes, but plenty of vapers believe dark liquids speed up clogging and noticeably shorten coil life.
Getting more life from a coil
There are really two approaches: change some of your vaping habits, or keep up with preventive maintenance so the buildup comes more slowly. In practice that means the following.
- Choose less sweetened or unsweetened juice when coil life matters to you.
- Turn the wattage down and pause between hits.
- Expect max VG and dark-colored liquids to wear coils out sooner.
- Keep the tank topped up, and do not fire the device unless you are drawing on it.
For reference, the longest we have kept one coil in use is 6 months.