If you vape, there’s a good chance that you’ve looked at your tank at some point and noticed that the vape juice was turning brown. Maybe you even noticed some brown or black staining in the formerly white wick openings along the side of the coil. In some cases, it’s possible for this color change to happen quite quickly. What’s happening here? Why is the vape juice turning brown in your tank, and should you be concerned about your safety?

As you’re going to learn from reading this article, there’s generally no reason to be overly concerned about a color change in your e-liquid. Most of the time, vape juice turns brown because of the natural oxidation that occurs in long-term storage. Although the oxidation likely means that the e-liquid won’t be as flavorful and potent as it once was, there’s no reason not to use it if you’re still happy with the flavor. 

When vape juice turns brown in the tank, though, it can also be an indication that the tank is in dire need of a coil change. In that case, you should definitely replace the coil right away because the coil is probably producing some substances that you don’t want to inhale.

How can you tell the difference, and what do you need to do about your brown vape juice? In this article, we’ll answer those questions.

Vape Juice Can Turn Brown if It’s Stored for a Long Time

One reason why vape juice can turn brown in the tank is because it has been stored for a long time and has begun to oxidize. Oxidation happens because of exposure to oxygen and light, and nicotine is particularly vulnerable to it. The more nicotine an e-liquid has, the more quickly it’ll oxidize. E-liquids containing tobacco extracts are also likely to oxidize rapidly. An e-liquid that has begun to oxidize will usually have a color ranging from yellow to light brown, although medium and dark brown colors are possible in some cases.

Usually, you can store vape juice for about a year after buying it and will notice little to no change in its color or flavor – but that’s if you leave the bottle closed and don’t open it until you’re ready to use it. If you’ve opened the bottle – and particularly if you’ve dispensed the e-liquid into a tank – you can expect the oxidation process to happen much more quickly. E-liquid that’s stored in a vape tank can potentially begin to show signs of oxidation after just a month or two. If you want your vape juice to last as long as it possibly can without noticeable degradation to its potency and flavor quality, you need to keep it in the original bottle.

So, what happens when an e-liquid begins to oxidize? As you’ve already noticed, the nicotine turns yellow and eventually deepens to brown. Oxidation causes nicotine to degrade, reducing the nicotine content of the e-liquid. The flavor of the vape juice will also change when it turns brown in your tank. Volatile flavors evaporate out of the e-liquid, and the remaining flavor notes begin to meld together. If you use e-liquid that has turned brown, you’ll probably notice that the individual flavor notes in the e-liquid are more difficult to detect than they used to be. 

Although oxidation does affect an e-liquid’s flavor and potency, you’re not likely to notice an enormous difference in either of those areas unless the vape juice has been in a tank for a very long time. As long as the vape juice still tastes good to you, there’s no reason not to use it unless it’s been in the tank for more than a few months.

Vape Juice Can Turn Brown Because of a Dirty Coil

Although a little oxidation in an e-liquid is generally nothing to worry about, there is another reason why the vape juice can turn brown in your tank – and in this case, it’s unwise to use the tank until you’ve resolved the issue.

When you vape, not all of the ingredients in your e-liquid actually turn to vapor. There are always impurities present in the vape juice that stick to the atomizer coil in your tank and create a film. The worst offender, however, isn’t actually an impurity at all – it’s sucralose, the sweetener that’s in a large percentage of today’s e-liquids. When sucralose is heated, it melts and forms a caramel-like substance. This residue – which the members of the vaping community have nicknamed “coil gunk” – quickly covers an entire vape coil and turns the coil black. Depending on how sweet your e-liquid is, a thick layer of coil gunk can form in just a couple of days.

If you’ve been using a heavily sweetened e-liquid for several days, the coil in your vape tank almost certainly has a thick layer of gunk. The gunk tends to create a dark, smoky flavor, but you might not notice it right away if the e-liquid you’re using is very sweet. If coil gunk is causing the e-liquid in your tank to turn brown, though, it’ll be obvious because the e-liquid will look dirty. It’ll be medium to dark brown, and you may even see black flecks floating in the tank. The wick holes on the side of the coil will be almost black if the coil reaches this point.

If your vape coil has developed such a thick layer of gunk that it’s turning the e-liquid brown, it means that you’re essentially inhaling burnt sucralose every time you vape. This definitely isn’t a good idea, and it indicates that you should replace the coil right away.

Coil gunk is an annoying problem, but it is possible to make your vape coils last much longer simply by using unsweetened e-liquid. Although most mainstream vape juice is sweetened these days, it’s still possible to find products that don’t use sucralose. If you’re happy with your current vape juice and don’t want to change it, that’s fine – but you should be prepared to install a new coil every few days if you don’t want to inhale coil gunk.