I once carried out an experiment on an unsuspecting colleague...
I gave him a new e-liquid and asked him what he thought.
“It’s okay, but nothing special,” he said.
A little while later we took him another e-liquid.
“This one’s brilliant - we love it,” I enthused.
Sure enough, he loved it too.
What he didn’t realise was that it was exactly the same e-liquid.
The point is that perceptions often cloud our judgement. (See The Psychology of Taste in our Vaper’s Tongue post.)
Some e-liquid lovers believe steeping is a waste of time. But others think it makes a huge difference.
But is that due to perception, or a real difference in taste?
For this blog post we decided to a blind steeping test to settle the matter once and for all. But first, let’s explore what steeping is, how steeping vape juice works and the different ways to do it.
What is Steeping?
Steeping refers to the method used to improve the flavour of vape juice.
This usually means allowing the e-liquid to sit for a period of time. E-liquid (also known as e-juice or vape juice) is sometimes shaken and (depending on the method used) exposing it to air. As we will see later in this post, a number of techniques are used to speed up the process.
Just like a fine wine, this process is supposed to improve the flavour of the e-liquid.
E-liquid is mixed from different ingredients.
The primary ingredients are usually propylene glycol, vegetable glycerine, nicotine and flavourings. It may also include other ingredients such as distilled water and alcohol. The idea behind steeping is to better combine these different properties.
What’s Raw E-Juice?
Steeping is particularly important when you are dealing with raw e-liquid. Raw e-liquid is a just-mixed e-liquid that may have little flavour.
What is Streathing?
Streathing is the process of testing your e-liquid to determine the perfect steeping time.Usually combined with a method such as warm bath steeping, it involves testing the e-liquid at different stages in the steeping method. Ideally, you’d keep taste notes on a spreadsheet to identify the perfect steeping times.
What is breathing e-liquid?
Breathing e-liquid is when you take the cap off to allow air to mix with the e-liquid in the bottle.
What is The Maillard Reaction?
When food browns, it is undergoing the Maillard reaction. This is a chemical interaction between amino acids and reducing sugars that gives the food different flavours. Examples include bread, toasted marshmallows and seared steaks.Some vapers believe that steeped e-liquid changes taste because of the Maillard Reaction. It is also referenced in our expert interview below.
Should You Steep Vape Juice?
Some vapers believe that steeping will never negatively affect taste.
Other vapers believe steeping makes no difference to taste.
You’ve probably heard elaborate tales of how cool, dark environments are the lifeblood of a “proper” vaping experience. You’ve probably been told how steeping allows flavors to ripen, like a fine Malbec. You’ve probably even heard that a well-steeped cartridge is more potent and strengthens the nicotine.
You heard wrong.
Source: White Cloud Blog
And then there’s stories like this:
For some reason my DIY mixes go the opposite way of popular opinion with regard to steeping - all my favourite flavours are usable immediately, and then gradually die away.
For example I do a Chocolate Mint to die for, but it's pretty much dead after a month or so. Heaven for two or three weeks, then past it. So I'd be a complete failure as a flavour artist in a vape business.
Chris Price of E-Cig Politics
So who’s right? To find out if steeping is all it’s made out to be, we decided to run an experiment
The Great Steeping Experiment
There’s no question that steeping changes the property of e-liquids. (Some even change colour.)
But does it improve the taste?
We’ve done some experiments in the past. In a blind tasting test using different flavours with 4 colleagues, we were able to distinguish between steeped and unsteeped e-liquids 70% of the time. (At times, though, we thought the unsteeped e-liquid was better.)
For this blog post we decided to run the test again. This time, we used experienced but independent vapers.
We only tested one flavour and one strength of 10ml e-liquid, and we didn’t send anyone two unsteeped or two steeped e-liquids. We know that some e-liquids respond better to steeping than others, so these results are unlikely to apply to all e-liquids.
In addition, bear in mind that everyone has a different capacity to taste e-liquid. It would be interesting to do this experiment with super tasters, who would be more likely to be able to taste the difference. (Fortunately, our Halo Tasting Panel does include a wine taster!)
We only managed to get nine tests completed. If anyone wants to repeat the test on a larger scale, it would be interesting to see how the results are affected by including a larger range of flavours, strengths. It would also be interesting to see if you could receive different results when you sent out exactly the same e-liquid.
Who Tested The E-Liquid
Huge thanks to the following vapers for participating in these tests:
(One vaper preferred to be anonymous, and is not listed here.)
To replicate what most vapers do, we decided to use a simple steeping test.
The steeped e-liquid was first mixed on the 05/02/2016. This was done as a whole batch, and then shaken vigorously until the liquid became very aerated (almost white in colour!). The e-liquid was then shaken intermittently for the next 2 hours before bottling.
Once the liquid was bottled, it was allowed to breathe for 12 hours with the cap off. Once the 12 hours was complete, it was shaken vigorously again.
The bottles were then stored in a cool, dark place, and were shaken daily until the 12/02/2016. At this stage, the bottles were then opened. The air within them recycled by giving the bottle a couple of squeezes. Once complete, these were shaken again and returned to the cool, dark place.
For the final process, the bottles were shaken daily until the 19/02/2016, at which point the air was once again recycled. After another shaking, these were left over the weekend before shipment on the 22/02/2016. You can probably guess that these were shaken once more before shipment!
How The Test Worked
Each tester was sent two bottles of Halo Vanilla Ice Cream E-Liquid.
One of them was from a batch steeped by our mixologist, Will. The other was bottled just before we sent out the e-liquid.
The bottles were coloured blue and black. There was no way to tell from the bottles which was steeped and unsteeped, and in fact our mixologist didn’t even tell me which one was steeped until after the experiment was over.
We asked the bloggers to rate the different flavours based on throat hit and flavour.
Steeped or Unsteeped: The Winner!
The results of the test couldn’t be clearer. Eight vapers who tried the e-liquid in the four days after the e-liquid had been sent out preferred the steeped version.What’s also interesting is the ONLY person who chose the unsteeped version was a late tester (more than ten days after the e-liquid was sent out). Steeping continues after a bottle is sent out, which could account for the different result.
How Steeping Affects Flavour
We also asked each vaper to rate each e-liquid between 1 (terrible) and 10 (excellent).
The mean rating for the unsteeped e-liquid was 6.33 and the rating for the steeped e-liquid was 8.11.
The really interesting difference was in the low scores given. One person gave the unsteeped version a 3, while a second person gave the unsteeped version a 4. However, the lowest score for the steeped version was a 7.
There was also a big difference in the high scores. Before our late tester, the unsteeped version receive a single score of 8, and no scores of 9. However, the steeped version received five scores of 8, and one score of 9.
Intriguingly, our late tester gave both e-liquids a score of 10.
How Steeping Affected Throat Hit
We asked each vaper which e-liquid had the biggest throat hit. The results were:
- Steeped e-liquid: 3 votes
- Unsteeped e-liquid: 5 votes
- Skipped question: 1
While it appears that steeping reduces throat hit, we’d really need stronger data to be sure.
Despite the limited data, our small test suggests that steeping can lead to a big difference in the taste of e-liquid.
How does steeping work: An interview with an expert
To dig deeper into the science behind steeping, we wanted to interview an expert.
It wasn’t easy to find someone who had both an in-depth knowledge of chemistry AND a practical knowledge of steeping - but we managed it.
Our expert combines a background in medicinal chemistry and mechanical engineering with practical experience in the mixing, steeping and production of e-liquid on a large scale.
Because of his position in the industry, he has requested anonymity in this post.
How does steeping work, and what causes the changes in taste?
There are several factors behind the flavour changes during the steeping process. These include both physical and chemical factors.
The ones occurring quite quickly are evaporation of volatiles and degasification.
Flavour concentrates often contain certain amounts of volatiles, which may not contribute final, overall flavour perception.
Very often vapours say that flavour is “too fresh” or “too sharp” straight away after mixing. In most of cases this sensation is created by the presence of small volatile molecules and small amounts of gases in the liquid. Normally they disappear, during the evaporation and degasification processes, within a few days.
Shaking bottles, from time to time, and leaving liquids with the cap off (or at least not tightly closed) helps to achieve better results quicker. That is why vapers say that they are “airing” their mixes.
Another physical factor is the homogenisation on the molecular level (by diffusion).
E-liquids, straight after mixing on the large scale, or “shaking” a DIY made bottle of juice are well homogenised as a whole volume, in a macro-scale. However, diffusion will still be occurring on the molecular scale.
After a couple of days e-liquids will get to the point of the equilibrium where not only all ingredients used are homogenised but where all the molecules coming with those ingredients re-arrange between themselves and the solvents (PG/VG).
The chemical factor of steeping probably involves, as normally happens in nature, reactions similar to the Maillard reactions or reactions occurring during the “browning process” or wine ageing. In general, this means that new, more complex flavour compounds are formed – i.e. esters, or oxidised aldehydes. A good example is browning of the vanillin-containing liquids.
These more complex molecules are formed at room temperature. However, this process takes longer and (in general) first changes in the taste can be observed after 3-5 days at least and may be occurring, at very slow pace, throughout whole shelf life of the product. It is a natural process, and shouldn’t be considered as unwanted. However, this can be slowed down by storing e-liquids in a relatively cold and dark place.
What’s the best method for a vaper to get maximum flavour?
Leaving DIY mixes in a dry and dark place, with the caps off (please don’t forget about safety, your children and pets!) Agitate them at least 2-3 times per day. All the natural processes discussed above should give significant improvement of the flavour and its perception after 5-7 days, and further changes will occur in the following weeks.
There is no general rule, as every blend is different. However, most of the liquids will significantly improve after a week’s time.
What’s the quickest method that produces results?
In theory storing liquids at higher temperatures (circa 40 oC) and degassing them in the ultrasonic bath will accelerate the whole process. However, I wouldn’t suggest doing that as it will always, even if leads to only a negligible difference, interfere with the naturally achieved equilibrium.
Does steeping leading to any changes in the chemical composition?
These changes are not major, but they will occur, as always happens with complex mixtures of varied molecules.
In fact, I would say that, from the chemical and physical point of view, “changes in the chemical composition and equilibrium are leading to the steeping”.
This kind of processes, regardless where and when, occur not only in e-liquids. Ageing is a rule of the whole universe, starting from food and beverages and ending in deep space.
Is there a danger of nicotine degradation?
As mentioned in the previous point, everything changes over time. I would not call steeping a danger, as testing and research shows that even very well-aged e-liquids are stable. Nicotine degradation process in e-liquids is very slow and takes years. (For more information see An Interview with Nicotine Expert Dr Jacques Le Houezec On E-Liquid: Storage, Safety and More.)
However, accelerated steeping (heating the liquids), may have an influence on nicotine degradation. Unfortunately, it is very difficult to judge all the DIY methods of accelerated steeping described on the forums. They may improve some characteristic of blends; however, they may have a negative influence on other factors of the e-liquids ageing.
How to Steep E-liquid
First: Heat, Light and Air
Firstly, you would usually keep your e-liquid away from heat and sunlight. These may lead to your e-liquid getting darker, and could speed up nicotine degradation. (This is not the case for accelerated steeping.)
The other thing to bear in mind is that if your e-liquid is exposed to air, impurities could get into your e-liquid. The propylene glycol in your e-liquid should kill any germs off, but it is still something to bear in mind.
Now, there are dozens of ways to steep e-liquid. Spinfuel magazine advises keeping it simple, at least to start with. But for the sake of completeness we have include a selection of different steep methods for you to play with! You’ll find many more on forums and Reddit.
The Slow Method
The first method simply involves periodically shaking your e-liquid, and the rest of the time leaving it in a cool, dark place.Most people will either remove the cap and leave the cap off, or periodically take off and replace the cap. However, E-Liquid Zine references an interesting experiment where steeping was carried out without removing the cap. The results were the same!
How long should you steep e-juice for?
Unfortunately, there’s no one answer. It depends on the e-liquid you use, and, of course, your personal taste. In fact, we find some e-liquids don’t need any steeping at all…
To get a clearer idea of steeping for different flavours, we asked our own mixologist, Will Brunton, to comment...
Custards and Complex Dessert Flavours
2-4 weeks is usually ideal. However, some flavours can be left even longer. Some people argue that these flavours continue to improve after several months of steeping.
Fruits and Menthol
Either shake and vape, or leave up to 2 weeks. Most fresh fruit and menthol flavours won’t require much, if any, steeping before use. Many of these flavourings react poorly to breathing in particular, and can lose flavour when this is done for too long.
However, more “creamy” fruity flavours such as Mango or similar can benefit from a week or two of steeping. The same goes for very complex fruit mixes, as this allows time for each component to “bond” and create the desired overall flavour profile.
Shake and Vape, or leave for 2-4 weeks. The majority of Tobacco flavours will benefit from a couple of weeks steeping. They tend to be quite complex flavours, and require this bonding time to really pick out the subtle flavour notes.
On the other hand, most tobacco eliquid vapers tend to be happy with the flavour when freshly mixed. I would argue that this is because some flavours used in tobacco are unfamiliar to the usual palette, so it will be difficult for most people to detect change even in a steeped bottle.
This does differ with Tobacco e-liquid containing flavours such as Caramel and Vanilla, as most people will notice the benefit and flavour improvement steeping such eliquids for 2 weeks or so.
Accelerated Steeping Methods
First, a quick thanks to all the many vapers who have experimented and documented accelerated methods of steeping. I’ve included a selection here, but you’ll find even more steeping methods listed in the resources as the end of this post.
At ECigaretteDirect, we’ve experimented with a magnetic stirrer to speed up the steeping process. The advantages are that air is mixed into the e-liquid at speed, but the results didn’t seem to be as good as leaving the e-liquid in a cool dark place for several weeks.
Various vapers have tried using an ultrasonic cleaner to steep e-liquid, with mixed results.Bobalex from E-Cigarette Forum uses a 2.5 liter ultrasonic cleaner to run e-liquid bottles through mixed warm and cold cycles. You can see his full description here.
Most vapers will tell you glass is best for heating methods. Glass retains heat better and melts at a much higher temperature.
However, the melting point of most plastic is comfortable above that of boiling water. In fact, while writing this post, I experimented with pouring boiling water on to a bottle of Halo E-Liquid. The bottle was fine.
That's not surprising - the melting point of the plastic used (PET) is 260 degrees celsius.
What about leaching chemicals, you may ask? That's a controversial subject, but the PET resin association claim that their plastic is very inert.
Even with glass, though, you avoid high temperatures. While warming can speed up the steeping process, too much heat can degrade the nicotine and flavourings.
- Heat some water. The water should be warm, not hot.
- Place the capped e-liquid in a sealed bag (some vapers recommend two bags.)
- Drop the bottle in the water, leave for 10-15 minutes.
- Remove the bottle and cap and shake. Test the e-liquid. Repeat until you get the desired taste.
Ideally, you would have water at a controlled temperature, but this is probably going a bit too far for the average vaper.
The Rice Method
Place a cup of uncooked rice in a microwave. Heat, then place the e-liquid in the rice. Leave till it reaches the desired temperature, remove, shake. Repeat process until the e-liquid achieves the desired taste.
Tie a bottle of e-liquid in a sock. Put it in the dryer and put the dryer on for fifteen minutes. Vapers who have tried this have seen a noticeable difference in the colour after just 15 minutes.They have also experienced damaged bottles and escaping caps, so be careful (and don’t use this method with glass bottles!)
The Hot Car Method
Put your e-liquid into the glove box of a hot car. Leave for a few hours, remove and enjoy.