The process of “steeping” is when e-liquids are agitated, gently heated and allowed to “breathe” in order to help improve the flavor.
There is some disagreement about the necessity of complex procedures, but effectively the goal is to allow any perfumey-tasting alcohol elements to evaporate off and to both protect the integrity of the flavorings and allow them to blend together or “mature.”
There are numerous different methods you can use to steep your e-liquids, but generally they involve shaking the e-liquid regularly, leaving it in a dark place and – at least periodically – taking the cap off to allow evaporation and circulation of air.
If you follow the general advice on e-liquid safety so far, you’ll be able to steep safely, but there are a couple of unique concerns that are worth addressing.
Find a cool, dark and dry place to steep e-liquid, following the same basic rules as when storing it.
Cupboards and cabinets are ideal, but if you’re using a box, make sure it’s put somewhere out of reach of children and pets – especially if you steep with the cap off!
Double-check that the cap is firmly screwed on before shaking, and if you squeeze air out of the bottle, don’t rush it.
There is little to no risk of bacterial or fungal contamination when you’re steeping liquids, but keep open bottles away from obvious sources of contamination!
All liquid steeps, changes color, and will slightly change flavor. It's like a big science experiment honestly. I will usually let liquids sit for about a week before I vape them. If you don't like a liquid at first, come back to it a few weeks later and see if anything has changed. – Nick “GrimmGreen” Green (GrimmGreen.com)
[Steeping safety is] essentially the same as storage. If you steep with an open lid, do so only while you can directly watch over the e-liquid. – Steve K (Steve K’s Vaping World)
Safe E-Liquid Steeping Practices
As when storing e-liquids, it’s best to find a dark, dry and cool place if you’re leaving liquids to steep for a while, to protect both the nicotine content and the flavorings.
The main difference is that because some vapers steep with the cap off (others merely remove the cap every so often and squeeze the air out of the bottle), you may need to find a location where there is no danger of it being moved around. Even if you have a locked box with an open bottle inside, a kid or pet could knock into it and leave you with a box of spilled e-liquid. Nicotine may not be as toxic as most people think, but it still is toxic. Cupboards and medicine cabinets are good choices for steeping, being dark, hard for small things to access and unlikely to be banged around, but if you have a box, choose its location carefully.
There is also a lot of shaking that goes on during e-liquid steeping, and this presents obvious problems with leaking or even spraying of e-juice if you don’t take a minute and ensure the cap is firmly in place first.
Additionally, when you’re squeezing air out of a bottle of e-liquid, don’t get too gung ho and create a nicotine-laced fountain! Squeeze gently until you see the juice approaching the dripper-top and leave it at that. If there are any spills, follow the advice from earlier in the guide: wash the area thoroughly, avoid contact with the juice where possible and make sure others won’t be exposed to any used paper towels or rags.
Contamination During E-Liquid Steeping
Opening the cap also effectively opens the door to the environment and potential sources of contamination within it. This is another reason it’s so important to ensure the place you leave your juice is free from obvious sources of contamination, and the surrounding area has at least been given a quick wipe beforehand. However, despite some concerns, there is no risk from contamination from fungus or bacteria in the air. Propylene glycol is a well-known anti-fungal and anti-bacterial chemical, and microbes need stuff to eat, so they can’t live in PG or VG.
There is no danger inherent in steeping your e-liquid as long as you exercise the same sort of caution you would any other time you handle and store your e-liquid.
Although it would aid the evaporation of alcohols and more volatile chemicals, if you’re concerned about safety, periodically taking the cap off and squeezing the bottle is preferable to letting it sit with the cap off for extended periods of time. It’s still effective and it reduces the risk of spills, but if you have a safe spot there’s nothing to be concerned about in either case.