The Enemies of E-Liquid: Heat, Light and Air
The basic rules for e-liquid storage come from an understanding of what you should keep your juice away from.
Nicotine expert Dr. Jacques Le Houezec points out that light and air will cause nicotine to oxidise, which results in a change of colour (but doesn’t affect its properties). However, he also says:
I would be more concerned about the flavours. They certainly degrade faster than nicotine.
Before going on to clarify:
It could change the taste, but should not change the effects. Some flavours, particularly tobacco flavours, or chocolate or coffee, can also turn dark with time, probably [due to light and air oxidation]. This should not be a concern, but I would recommend to keep them cool and away from light.
This advice is in agreement with material safety data sheets and general advice offered by the companies that sell e-liquid flavourings.
How Does Heat Affect E-liquid?
The problem with heat comes down to how chemical interactions work in general:
if something is hotter, its molecules have more energy, and this could be enough to allow them to interact with other ingredients or to break down into smaller components.
This wouldn’t be an issue, but the specific compounds create the flavour notes in your e-liquid, so if any of them change, it will alter the taste of your juice.
How Does Light and Air Affect E-liquid?
The reason you’re advised to avoid light and air comes down to the effect of UV light and oxygen on nicotine.
The oxygen reacts with the nicotine to produce cotinine (this “oxidation” process involves the loss of two hydrogen atoms and the gain of one oxygen atom) and the UV light helps this process along by providing energy in a similar fashion (but not in exactly the same way) as heat does. The more the reaction occurs, the less nicotine will be left in your juice, but in most cases the effect won’t be noticeable – unless you’re really careless in your storage.
The issue with oxygen can’t be completely avoided, because some will be dissolved in your juice even if you have a full bottle with no “headspace” above it, but the effect will be minimal as long as you keep it away from light.
The basic message is simple: keep your e-liquid away from heat, light, and – where possible – air. (And zombies!)
