Why does e-liquid turn brown?

While in most circumstances your bottle of e-liquid will be used up within a matter of days, there are those that slip to the bottom of a bag, or back of a drawer and get forgotten about – if they stay lost for long enough there is a good chance you will notice that the e-liquid within has started to turn brown, or at least a darker shade than it was when you first bought it.

Equally, you may be experiencing an even more common issue, in that your e-liquid is turning brown once in your vape tank itself!

Whichever of these applies to you, below we will explore the typical reasons for this colour change, how you can prevent it, and whether or not it is safe for you to continue vaping an e-liquid that has started to turn brown.

How long does e-liquid normally last?

E-liquid usually has a shelf life of between one to two years depending on the flavour and base used. However, in reality the ingredients used to produce an e-liquid can remain microbiologically stable for up to ten years if stored correctly.

The reason manufacturers apply expiry dates to vaping products is actually more directly intended to prevent people from vaping liquids that have over-steeped or turned unappealingly dark in colour.

With that said, we absolutely do not encourage you to begin ignoring the use-by dates provided on your e-liquids, they are there for your safety and to ensure your vaping experience is consistently enjoyable. If you do accidentally consume an e-liquid that has expired, do not panic – the immediate risk is very minimal beyond it simply tasting from odd to awful.

Why does e-liquid turn brown when it comes into contact with UV rays and oxygen?

Oxidisation and photosensitivity are two of the most common processes that can cause your e-liquid to turn darker in colour. In either case, the colour change is directly linked to the product’s nicotine content. While turning darker or brown may be perceived as a negative, it can actually be an accepted side-effect of a process carried out by many vapers known as steeping.

What is Steeping?

Steeping is a process carried out by vapers who wish to optimise the flavour of their chosen e-liquid, in-line with their personal preferences. EDGE E-liquids are all steeped in our factory as a part of the mixing process for a pre-determined amount of time depending on the flavour, so our bottles always taste their best when they reach our customers; this does not necessarily mean our customers wouldn’t steep their EDGE e-liquid even more after purchase – it is a matter of personal taste.

There are a few different methods employed by vapers to steep their juice, some leave them for long periods of time in warm and dark places, others shake them or even use sonic baths, and some simply leave the lid off the bottle for however long they see fit – in many cases it can be all of the above.

The ultimate goal of steeping your e-liquid is to develop the flavour profile until it reaches a level you are most satisfied with. Steeping an e-liquid typically makes a flavour stronger and more defined, but can also soften harsher chemical notes which are most common in cheaper e-liquids using less premium flavourings.

The reason this occurs is because many of the food-grade flavourings used in e-liquid manufacture, contain different amounts of ethanol or similar food-grade alcohols. This is because they are an excellent carrier agent for the highly concentrated compounds that go into almost all food flavourings, allowing them to be properly blended into an e-liquid recipe. Some people can be particularly sensitive to this alcohol content, however minimal, which can translate as harsh or chemical notes in the products flavour profile or aroma.

As the steeping process is carried out, this alcohol content evaporates and effectively removes these harsher notes. At the same time, shaking or agitation can cause some ion exchange and bonding between the different flavour compounds in the concentrates used for the e-liquid’s recipe. This combination of processes results in a more defined, and often smoother e-liquid to vape – but how long a product should steep is entirely down to personal taste and is far from an exact science when carried out at home.

No matter your technique, steeping will almost always come with the side-effect of turning your e-liquid a darker shade of yellow, or even brown. This is because the nicotine within the recipe begins to oxidise when exposed to the air.

What is Oxidisation?

Oxidation is a natural process that can affect a number of different materials. Examples of this include the rusting of ferrous metals as oxygen steals electrons from the host metal, or when different kinds of fruit such as bananas or apples turn brown when they are left out for a few days. The nature of the material often dictates the way in which oxidisation impacts it.

In e-liquid terms, the oxidisation caused by the steeping process has an impact on the compounds within the flavour concentrates, but most notably on the nicotine. The exposure to oxygen breaks down the nicotine as oxygen molecules bind to it. This breakdown is largely responsible for the colour change observed over time.

What is Photosensitivity?

Whether or not you understand the science behind the process, most people will have experienced photosensitivity and it’s results. Sun bleaching is a good example – in a room with old carpet where the furniture hasn’t moved for a long time it’s common to find that the colour of the carpet beneath the furniture is deeper and true to when it was dyed. The areas that have been exposed to sunlight over the years however, are often faded by comparison.

This occurs because the radiation from UV rays is damaging to many materials, including our own skin if we stay in the sunshine for too long without protection. These rays impact e-liquids much in the same way. Excessive exposure to direct sunlight over a long period of time works in tandem with oxidisation to change not only the colour of the e-liquid but also potentially reducing its potency.

Through these two processes the nicotine can lose two hydrogen atoms and gain a single oxygen atom. This effectively turns nicotine into another substance, cotinine. While cotinine is still safe to vape, it may not provide the ‘hit’ a vaper is used to, leading to the claims made by many vapers that the old liquid they tried didn’t satisfy as expected.

Is ‘over steeped’ e-liquid safe to use?

While there is no research to suggest that older, expired or simply over steeped e-liquid is dangerous, your vaping satisfaction may be reduced somewhat if the nicotine loses its strength, or if you are not partial to the flavour it provides. Let alone the visual impact of the dark colours they can turn.

If your bottle has turned a darker colour or has an odd taste or aroma compared to your expectations, it is often best to simply throw it away responsibly. E-liquids you buy from a store should always be on a colour spectrum from clear to amber (with the exception of those brands who add artificial colours – EDGE do not.) Anything darker than this should be questioned as it is entirely possible that the retailer may be selling a bottle that has been on their display for a long time, without understanding the implications of correct e-liquid storage.

Over steeped e-liquid can cause less savvy vapers to assume their coil may have burnt out when it is not the case – you can learn more about this by checking out Why do my coils keep burning out? Or to learn more about vaping basics, check out our comprehensive guide: How to Vape Properly.