Dark e liquid cause and why it is dark

Dark e liquid: nothing to worry about!

Discoloration what any product to be consumed or applied can cause anxiety and disgust. The same applies to dark e liquids. However, this is where further knowledge of such a chemical reaction comes in handy. Many vapers throw out their e-juice bottle simply because its colour differs from when they first purchased it. Little do they know, that there is nothing actually wrong with their e-liquid.

In previous articles, such as Storing E liquid and why the fridge and freezer are not the best solution and Improve E Liquid Flavour – 7 best practices , we have thoroughly discussed how to store your e juice. In these the effects of storing e juice incorrectly we generally explained. However, what happens to the liquid once stored for a more extended period of time was not explored in detail.

Let’s investigate in a more scientific approach what happens with our vaping liquid.


One reason why a colour change can occur is oxidization, a common chemical reaction where a substance comes into contact with oxygen. In our case, this substance is nicotine. Even if stored in a dark, cool place, e-juice containing nicotine will gradually darken in colour. Exposed to light, air, and heat, the speed of this process will increase, and the stronger the e-juice – i.e. the more nicotine content in the bottle -, the faster the discoloration. Some e juice manufacturers add preservatives or stabilizers to the liquid to slow down this process; however, in the long run, it is inevitable.

It is important to know that this chemical reaction does not affect the quality of the vaping liquid. Both darker and transparent, lighter juices are perfectly safe to vape, and will not affect taste. Discolouration does therefore not signify expiration.

Time does not affect the density either. Despite appearing thicker once the liquid has gained a darker colour after being stored for a longer time, there is no actual chemical reaction taking place that would change the thickness.


Another reason for discolouration are the sweet ingredients and substances within the juice. Manufacturers tend to add artificial sweeteners and sugars to the juices, while VG (vegetable glycerin) juices are found to be sweeter than PG (propylene glycol) juices. Exposed to intense heat, these sugars caramelize on the atomizer coil creating the so-called “gunk,” a sticky caramel-like substance. Thanks to its brown colour, gunk lends a darker shade to the liquid. Additionally, it leaves behind a residue in our atomizer and tank. Because of this, it is better to clean the atomizer and tank before each refill; otherwise, the gunk will darken and compromise the taste of other e-juices added to the e-cig.

Darkening your e juice on purpose

Some vapers in fact prefer their e liquid to be darker and more mature by “steeping”, though not in the same sense as you would steep tea. Steeping in the vaping dictionary is pretty much like letting your juice age. The process is fairly straightforward, as storing e liquid in a cool, dark place for as long as desired. As a result, the ingredients have more time to mix, creating a shift in the flavour and giving the e-juice a more mature aroma.

Overall, discolouration of e-juice does not reflect poor quality or expiration. Although the taste may be slightly different, the enjoyment and feel remains the same.

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