Steeping (in vaping terminology,) is the process in which you are either forcing or allowing the eliquid to mix evenly at the molecular level.
The actual technical term is homogenization, which questions why we use the term “Steeping” in the first place.
The term “Steeping” actually refers to putting a solid into a liquid to soak in order to soften, cleanse or to extract a given property from.
Some eliquid producers actually use this process to extract real flavours, especially with tobacco flavours.
Incorrect terminology aside, lets move on to the real subject.
As we know, eliquid is usually made from 4 main ingredients although, there is an unimaginable amount of combinations, variations and additions to the basic recipe, the reason for steeping is exactly the same.
The basic ingredients of eliquid are: Propylene Glycol, Vegetable Glycerine, Flavouring and Nicotine.
Each ingredient is of different viscosities which means when placed in a bottle together, they don't actually mix together at the molecular level although through the naked eye, you wouldn't be able to tell. If you had a microscope, it would look something like this:
What the steeping process does, is turn the Heterogeneous mixture into a Homogeneous mixture which would look something like this:
There are a number of methods which have been reported to work including, whisking, leaving them on a radiator, even sealing bottles of eliquid to the inside of wheel trims (hub caps) before going on a drive. No matter which method works for you, eventually all eliquids will reach a point where they are "steeped."
One of the most simple and effective methods is the natural steep. To archive a natural steep, simply remove the cap and the dripper, put your bottle of juice in a safe, dark place and leave it from anywhere between a week and a month.
This method takes by far the longest to achieve a homogeneous state as you are relying on the molecules themselves to move each other until they are evenly mixed.
One of the most common ways of speeding up the process is by using an Ultrasonic cleaner.
What this does, is vibrates the eliquid at a very high rate, at the same time as heating the liquid up which in turn, forces the molecules to move around much faster, causing them to become even at a much quicker rate.
This can lower a steeping time from 3 weeks using the natural method to 24 hours if done correctly.
The outcome of all of this is a much more bodied, rounder, flavourful vape. Where you might not have tasted some flavours when the juice was new, flavours come out and are richer and more defined.
Away from vaping, homogenization is used most obviously in milk processing although, that is done by forcing the milk through tiny valves at extremely high pressure.
Homogenization is also used in Science Labs however, they use Ultrasonic Homogenizers and have some really amazing results.