Why is my e-juice changing color?
The change in color is a natural, chemical reaction known as oxidation. When exposing your e-juice to oxygen, light and/or heat the nicotine based substance may turn a very light brown.
Another known cause is the caramelization of 100% Vegetable Glycerin (VG) based e-juices. VG tends to be sweeter than Propylene Glycol (PG) and has a viscosity similar to syrup. The heat produced when vaping causes the VG to caramelize on the atomizer coil.
This black/brown e-juice buildup is commonly referred to as “gunk” and it stains the remaining e-liquid. As the level of the e-juice in the tank decreases the discolouration becomes more visible.
Whether the culprit is oxidation or caramelization, the color change is nothing to be concerned about and is a common occurrence.