Hidden science behind normal and accelerated e-Liquid steeping

Hidden science behind normal and accelerated e-Liquid steeping.

We are all aware that steeping an e-Liquid can improve its flavour and change its colour.
Here I am attempting to describe the cause and effect systems involved in steeping and accelerated steeping from a moderately scientific viewpoint.

There are two major processes involved in steeping e-Liquid

1. Removal of volatile components by evaporation and degasification

This process would include the removal of alcohol but is not restricted to alcohol, there are other volatile components used in the production of flavour concentrates that generally give off an astringent or chemical odour.

These process requires access to the atmosphere hence the need to remove tops from bottles

1a Evaporation – This is the same process as used in cooking to remove alcohol from wine.

1b Degasification – This is the same process as letting a fizzy drink go flat

Both of these processes are accelerated by heat and increased surface area.

This is a critical first step many e-Liquids are hideous and un-vapeable before this process.

Without acceleration this can take a week or longer due to the viscosity of the liquid.

2. The development of complex flavour molecules.

Over time some e-Liquids especially custard / caramel or desert flavours darken over time
From observation this cannot be oxidation as it occurs uniformly through the liquid and does not require agitation of the liquid to occur.
It also cannot be caramelization as this does not occur below 110°C.

Maillard Reaction - Colour and flavour

What seems to be happening is a Maillard reaction commonly experienced by most people every day. The browning of bread, toast and potato chips these are high temperature examples. Medium temperature examples creating Dulce de leche and condensed milk.
Mallard reactions also occur at lower temperatures and contribute to the aging of wine and Balsamic Vinegar.

Maillard reactions get exponentially slower as they progress
This fits in with our observations of steeping e-Liquid, a golden colour may be observed in a couple of days however the full desired flavour and colour may take 4-6 weeks to develop.

The Maillard reactions will continue to progress over time, hence those almost black bottles of e-Liquid that are found at the back of a draw.

The degree of colour change is dependent on the type of flavours present and the presence of Nicotine
Some flavours wont change at all these are often referred to as shake and vape liquids.
This mirrors the culinary world, you never see matured lemonade being sold.

Accelerating the steeping process

Removal of volatile components by evaporation and degasification

a) Taking the top off the bottle.

Evaporation and degasification simply wont happen with the lid on (Think bottle of lemonade)

b) Shaking the bottle (Helps)

c) Stirring (Helps)

d) Whisking (Very effective)

c) Blending to a foam (Super Effective)

d) Ultrasonic degasification (Super Effective)
Video showing ultrasonic degasification

d) Heating to 40°C-50°C (Accelerates all of the above methods)

Maillard Reaction - Colour and flavour

a) Heating to 40°C-50°C (Maillard reactions go slower at lower temperatures)

b) Ultrasonic treatment (local extremes of temperature and pressure act as a catalyst)

In Practice

The image on the left was taken immediately after mixing the image on the right was taken 5 Hours Later

60:40 VG PG 18% Nic 15% T-Juice Custard Concentrate

The e-Liquid was very vapeable the next day and is continuing to improve in the bottle.

Method used

a) Mixed liquid by weight directly into the blender cup.

b) Blended to a foam for 15 seconds remove lid

c) Placed into ultrasonic bath pre-heated to 50°C

d) 20 minute ultrasonic cycle

e) 20 minute rest

f) repeated (b) to (e) above six times

Then bottled into 50ml bottles

Storing after accelerated steeping.

Storing lid off in warm (room temp) draw or cupboard will allow any new volatiles to escape
This is less important as time passes.

The e-Liquid will continue its Maillard reaction gaining in richness, complexity and darkening

There will be a point where you will not want the process to continue this is of personal preference.
This dictates how much you should make. As the Maillard reaction slows down most e-Liquids have a “Window of Niceness” lasting a couple of months.

The process can be slowed by refrigeration don’t freeze your liquid.

Quality and Issues

There is no quality related advantage accelerating the steeping of e-Liquid.

Some of the top note flavours may be lost through aggressive evaporation.
losing the freshness and crispness associated with fruit flavours is an example.

Heating some flavours may introduce an unwanted cooked flavour

If the acceleration process is overdone the “Window of Niceness” shelf life can be drastically reduced.

Full blown blending is impractical for quantities of less than about 100ml

Good old lid off in a dark place with a bit of a shake now and then will result in a perfectly steeped e-Liquid it is also far more predictable than accelerated steeping. It just takes longer.

As there are so many variables involved, you should always keep notes on how you
have steeped your e-Liquid****along with the ingredients. You can then easily replicate your successes.
The easiest way to do this is by using the http://e-liquid-recipes.com calculator and adding notes to your recipes


Wikipedia entry on Maillard reactions

Description of low temperature Maillard reactions


Joe Dyer 11/06/2015


Nice. Is this your work? :smiley:

very informative!!! thanks

Yes it is my work
The physical methods are widely used by several people.
I felt that the underlying reasons for the real world observations were misunderstood.
This is not surprising as the two main processes involved in steeping produce very similar results and are also accelerated by the same methods.

I still have some experiments to do:
One involving the Maillard reaction and a digital PH Meter. (Acid is an inhibitor)
Nicotine is an Accelerator as it is an alkaloid
The other involving water apparently water is both an inhibitor (when there is too much)
and an accelerant when there is just a little , helping the mobility of molecules

I have been experimenting with the physical properties of PG and VG solutions for a number of years
I manufacture high speed photographic equipment that takes images of colliding liquids


Very interesting stuff - I can’t wait to read more! :smile: Good work! And thanks for sharing it!

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In order to look at some of the other variables the steeping will have to be done under normal un accelerated conditions.
One will be to add acidic components of a mix later in the process after initial steeping.
This is very often done in cooking sometimes with the same ingredient so the dish has a mixture of Maillarded
(did I just make a word up) and un Maillarded ingredients.
Tomatoes in Italian cooking and Onions in Indian cooking come to mind.

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Very cool! I’ve been waiting for someone to prove or have an acceptable method of accelerated steeping. There are a lot of impatient DIY vapers out there! Bookmarked this for further reading and test results.

Excellent presentation.

I wish I could explain how vaping with Clapton wire has it’s advantages over standard coils… And how it effect flavor. I’m sure it’s a lot more than surface area.

With clapton you have a wick around your wire, a metal one. So you get almost genny like flavour. Your cotton inside is more like a liquid container, not a wick, because it doesn’t heat up as much as with micro coils. That changes the flavour a lot and also improves juice supply.


RiP Trippers has just done Tutorial build of Fused Clapton Coil
Towards the end he shows the coil itself wicking,
It is his opinion that this gives the increased flavour, looks convincing to me


I’m thinking this is the little air bubbles that appear and race through the liquid. It really fascinated me to the point that I made a 20 minute video of this occurring.

This is @UncleJoe’s post… I’m just sharing in the conversation.


This is very interesting! Thank you very much for posting. I guess I’ll have to buy a milk frother after all. I would really love to automate the whole steeping process so it works fully repeatable and without having to keep an eye on it.

But I’m a bit skeptical. Please don’t take offense, but can anyone peer-review this? Does anyone know if this mallard reaction really applies to the tobacco / custard flavours that mostly need steeping? What is strange about this is since the flavours are already suspended in PG why doesn’t the mallard reaction already occur in the flavour bottle before being diluted? In effect why then can’t flavour be pre steeped if it’s a chemical reaction?

A while back I read that intermolecular forces are the reason we need steeping (basically mixing so the flavour molecules lightly bond to PG/VG or something - I’m not a chemist). I’d love to hear /u/Valligo take on this. Of course Valligo doesn’t reveal the actual steeping methods so that article might just be marketing.

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I think I mentioned it before that the coils @newdrip and @Jondamon are making wick without cotton it’s similar to mesh…

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Very true a lot of the coils have juice channels to capture the juice especially so in the ones that are fused with more wire.

I wouldn’t be wrapping the coils I am today though if it hadn’t been for @NewDrip guiding me through with his metal master ways.



I do understand @UncleJoe’s theory and on a side note I always thought of it as a wine making process. The steeping is really aging until it’s ripe. One way I’ve heard the steeping process described is at first mix you billions of individual molecules, (different flavorings, pg,vg, nicotine) all together but still separate. Overtime the molecules bind together to create one uniform molecule and that’s your finished eliquid. Some molecules take longer than others to bind, thus a longer steep time. @UncleJoe has proven that this binding process can be sped up a bit.


Great, great information. One question though : will introducing air into the mixture by blending or whipping cause any oxidation?


Good read ! Great info for the forum


I like to steep by just putting it in the cupboard with the lid off for a couple of days and intermittent shaking. How long is it best to leave the lid off though please?

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This is open to debate.

I used to leave lids off for a day then cap and shake every day.

@Ken_O_Where doesn’t recommend leaving caps off at all as flavour molecules can dissipate too.

Maybe he’ll get back in on this discussion and advise further.

I’m currently steeping 2 batches without any heat source and without opening the caps to see if there’s any noticeable difference to my previous mixes.

Over to you Kustard Ken. Lol.



Great to see the debate opening.
I do mention potential loss of flavour with accelerated steeping.
A common technique in cooking is to add delicate aromatics later in the cooking process
So maybe with an Apple Pie and Custard e-Liquid the Apple could be introduced after the initial steeping.

I have also tested the alkaline theory by adding 10% of saturated sodium bicarbonate solution to a 0 % custard e-Liquid
The result was an almost chocolate brown liquid after a week. The original is still yellow and unchanged.