Have you ever looked at your favourite bottle of e-liquid and asked yourself why the liquid appears to have changed colour since you bought it?
If the answer is yes you may also have questioned other physical properties of the e-liquid. For example:
- Is the liquid “thicker” when the colour is more intense and “waterier” when the liquid is clear?
- How is the taste of the flavour effected by this colour?
- Do I prefer the flavour when the e-liquid has been stored on my shelf at home for a few weeks? Or do I like it straight from the bottle when it was bought?
All interesting questions, I’m sure you’d agree. We all know one of the big appeals of e-liquid is the personal journey it allows vapers to undertake.
Perception of taste, colour, and even e-juice thickness is a matter of personal opinion. However, we can use a little bit of science to help reaffirm our observations. To re-examine what we think we know! Let’s take a look at some Totally Wicked e-liquid and see what happens to them over an extended storage period.
E-liquid changing colour
We looked at 5 different batches of Red Label Bubble gum 0.6 %. Stored in a sample library, at room temperature. The date of manufacture (D.O.M) indicates the age of the liquid. The bottles ranging from freshly made, to being over 12 months old.
The freshly made e-liquid is clear, with a slight tinge of yellow. As the maturing of the e-liquid progresses, the colour changes from tinge of yellow, light orange, and finally darker orange. If your nicotine strength is higher, the liquid will become even darker in time.
What is the cause of the e-liquid colour change?
One reason for the liquid colour change is a process caused by oxidation, the gain of oxygen by a substance. It is important to note the colour change due to oxidation is expected and accounted for in the product specification to which Totally Wicked manufacture all e-liquids.
Which substances are being oxidised? The first is nicotine, albeit at a slow rate. When nicotine containing e-liquid is stored at room temperature, the combination of light and air will cause the liquid to darken over a period of time. This darkening can be enhanced by the e-liquid strength. Which is quite logical as higher nicotine concentration in the bottle will result in a darker appearance.
Does this mean it has gone off?
No, don’t worry. Our laboratory stability tests have shown this nicotine oxidation process to be slow at room temperature, in a variety of e-liquid flavour formulations. The darker e-liquids are still the same quality as the newly formulated, clear e-liquid.
The type of flavour can also have an effect on the darkening of the e-liquid. For example, a custard flavour like Diavlo “the Judge” will darken more significantly. Even at low nicotine strength, due to the presence of specific flavouring ingredients.
Does the e-juice thickness stay the same?
Yes. The thickness (viscosity) of the e-liquid is consistent between the light-coloured sample and the darker liquid. No chemical processes are occurring over the storage period to significantly alter the thickness.
Sure, the diluent (PG/VG) will pick up a little bit of moisture from the air during the maturing process, but not to the extent where a vaper will notice a difference in the thickness of the e-liquid. What will change is how we perceive the e-liquid colour through our visual sense. The e-liquid stored for over one year simply looks thicker due to the darken colour and the newly manufactured e-liquid looks thinner or “watery”.
Perception through taste and smell
Let’s again use the example of Red Label Bubble gum. The processes by which flavours mature, and our perception of the flavour through taste and aroma, are complex and too numerous to cover in this article.
Some vapers will prefer a flavour which has been left to mature for several weeks (commonly known as steeping, if indeed the term is not scientifically accurate for e-juice!). Whereas other vapers will not perceive any difference between a freshly formulated e-liquid and one which has been allowed to mature.
While the complexities of e-liquid formulation are such that this article cannot cover them all, this is the condensed explanation that hopefully answers some of the key questions.
The colour changing should have little to no impact on the taste of your favourite e-liquid.
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