1. Flavors can often exhibit color changes without any affects on taste or functionality. There are a variety of reasons why flavors may vary in color over time or between order to order. Heat, light, and oxygen exposure are the most common factors causing color changes in flavors over time. For example, take an apple that is cut fresh and compare it to an apple that was cut an hour before. What you will see is a slight change in color, but if you did a blind taste test, you would not be able to detect any flavor differences. Also, since many of the flavoring ingredients are from natural sources, crop variations from harvest to harvest can often explain hue changes. Flavoring ingredients may also be specified with a range of color from our suppliers, and these slight deviations can translate into our finished flavors.
2. First, let’s talk about the way e-liquid changes color in the bottle, sometimes even before it has been opened. This is the result of a common chemical reaction known as oxidation. Nicotine is a very reactive substance, and can cause e-liquid to change color either in reaction with other ingredients in the juice, or after being exposed to air, light or heat. Nicotine-containing juices tend to become darker over time, even when stored in cool, dark places, but some companies add small amounts of preservatives or stabilizers to prevent oxidation.
However, the important thing to keep in mind is that oxidation is a natural chemical reaction which does not alter the taste of the e-liquid or your overall vaping experience in any way. You wouldn’t believe how many people throw away perfectly good e-liquid thinking that the discoloration is a sign that it has gone bad and is no longer safe to vape. Really old, nicotine-containing e-liquid can become almost black, but it is merely a cosmetic change that really shouldn’t worry anybody.
Oxidation occurs even faster in the clearomizer, where the nicotine is exposed to high levels of heat. The higher the nicotine content of your juice, the more visible the effects of oxidation, but again, with no implication on its taste or vapor production. Think of the oxidation of apples or potatoes after you’ve pealed away the skin – they become darker, but they taste the same. Think of it this way, if your e-liquid changes color, it’s probably more “natural”, as it probably contains no chemical substances that prevent oxidation.
But oxidation is not the only thing that causes e-liquid to change color. Vegetable glycerin-based juices tend to be sweeter than propylene glycole ones, regardless of the flavor, and the extreme heat causes them to caramelize on the atomizer coil. This “gunk”, as it’s commonly known in vaping circles, stains the e-liquid, an effect that becomes increasingly visible as the level of juice in the tank decreases. In extreme cases, 100% VG-based juices can start off as clear, amber-colored concoctions and become dark-brown goo by the time you reach the end of the tank. Simply adding fresh e-liquid will only cause it to darken even faster due to the gunk buildup on the coil, and the residue left in the tank.
Since this “caramelization” ultimately affects not only the color but also the taste of the e-liquid, it’s recommended that you clean both the tank and the atomizer before refilling. Of course, cleaning can only do so much, and you’re eventually going to have to replace the coil and wick of your atomizer, or use a brand new one, if it’s a disposable. It’s worth remembering that gunk buildup is closely tied to the sweetness and viscosity of the e-liquid; for example, a thick, sweet juice will caramelize much faster than a PG-based tobacco e-liquid.
Whether caused by oxidation or caramelization, a change in the color of your e-liquid is nothing to worry about. It’s actually a common occurrence, and if it hasn’t happen to you before, it’s probably because you’ve either been using nicotine-free juices or clear, PG-based unsweetened ones.
I heard about e-juice cracking some kinds of tanks. How do I know if an e-liquid will crack my tank?
If you use an e-liquid delivery system that has some sort of plastic tank, like some clearomizers and rebuildable atomizers, there are some e-liquids that may cause your tank to crack over time. Generally, it’s recommended that you use a device that doesn’t have a plastic tank. Anodized aluminum, stainless steel, and glass are all recommended over plastic.
However, if you do decide to use a device with a plastic tank, you may want to avoid e-juices with citrus, menthol, anise (licorice), or other acidic flavorings, as they may damage some plastics over time.
How should I store my e-juice?
Ideally, you want to store your e-juice somewhere cool (not higher than room temperature) and dark. Light can adversely affect your e-juice, and it’s especially important to store them somewhere dark if the bottles are clear. You also want to keep them away from pets and children, like you would any product containing nicotine. It is a poison, after all.