E-liquid formulations are typically built around four main ingredient groups: vegetable glycerine (VG), propylene glycol (PG), nicotine and flavourings. Each serves a different purpose, influencing characteristics such as viscosity, flavour delivery, vapour production and the overall formulation.
However, developing an e-liquid is not simply a case of combining these ingredients. Their proportions and characteristics need to work together for the intended product format, nicotine strength and vaping device.
This guide explains the role of each core e-liquid ingredient and how they come together when developing a finished formulation.
Most e-liquids are formulated using a combination of four main ingredient groups:
Not every e-liquid contains all four. Nicotine-free formulations, for example, contain no nicotine, while the balance of VG and PG can vary considerably between products.
The important distinction is that these ingredients do not work independently. Changing the proportion or specification of one component can influence other characteristics of the formulation, including its viscosity, flavour profile and suitability for different vaping devices.
This is why an e-liquid formulation is better understood as a complete system rather than a fixed recipe. The appropriate combination depends on what the finished product is intended to achieve.
Vegetable glycerine (VG) is a clear, relatively thick liquid that forms one of the main base ingredients in many e-liquid formulations. It has a naturally mild sweetness and is widely used alongside propylene glycol (PG) to create the liquid base that carries nicotine and flavourings.
One of VG's most noticeable characteristics is its viscosity. Increasing the proportion of VG generally creates a thicker e-liquid, while also contributing to greater vapour production when the liquid is heated.
This makes the VG content an important consideration when developing an e-liquid for a particular product or device. Higher-VG formulations are commonly associated with products intended for greater vapour production, whereas formulations designed for smaller, lower-powered devices will often require a different VG/PG balance to support effective liquid delivery to the coil.
VG can also influence the way a finished formulation behaves beyond vapour production. Its proportion needs to be considered alongside the flavour system, nicotine format and other ingredients rather than being selected in isolation.
There is no single VG percentage that is right for every e-liquid. The appropriate ratio depends on factors including:
For a manufacturer, the aim is therefore not simply to maximise or minimise VG, but to establish a ratio that works as part of the complete formulation and its intended application.
Propylene glycol (PG) is a clear, relatively thin liquid commonly used alongside vegetable glycerine as a base ingredient in e-liquid. It also acts as an effective carrier for flavourings and nicotine, helping distribute these components throughout the formulation.
Compared with VG, PG has a much lower viscosity. A higher proportion of PG therefore produces a thinner e-liquid, which can make it easier for the liquid to move through the wicking material within certain coils and pod systems.
PG also plays an important role in how an e-liquid delivers flavour. Its properties make it particularly effective at carrying flavour compounds, while the VG/PG balance can influence the overall sensory characteristics of the finished product.
Another characteristic associated with PG is a more noticeable throat sensation when inhaled. The extent of this will also depend on other aspects of the formulation, particularly the nicotine type and strength, so PG should not be considered independently.
As with VG, there is no universally correct PG percentage. The appropriate proportion depends on the type of e-liquid being developed and how it is intended to be used. Factors to consider include:
VG and PG therefore work as a balance. Adjusting one inevitably changes the proportion of the other and can alter several characteristics of the finished e-liquid at the same time.
VG and PG both form part of the base of an e-liquid, but their different properties mean the ratio between them can significantly influence how the finished formulation behaves.
Neither ingredient is inherently better than the other. The appropriate balance depends on the product being developed, its intended device and the characteristics the formulation needs to deliver.
| Characteristic | Higher VG | Higher PG |
|---|---|---|
| Viscosity | Thicker | Thinner |
| Vapour production | Generally greater | Generally lower |
| Flavour delivery | Can soften flavour perception | Effective carrier for flavour compounds |
| Throat sensation | Typically softer | Typically more noticeable |
| Wicking | Requires suitable wicking and coil design | Flows more readily through wicking material |
| Formulation considerations | Often suited to products designed for greater vapour production | Often suited to formulations where lower viscosity is required |
Common ratios such as 50/50, 60/40 and 70/30 describe the proportion of VG to PG within the formulation. However, these numbers should not be treated as quality grades or a simple progression from one type of e-liquid to another.
For example, a 70/30 formulation is not inherently “better” than a 50/50 formulation. Each creates different physical and sensory characteristics and may be more or less appropriate depending on the intended application.
When developing a commercial e-liquid, the VG/PG ratio therefore needs to be considered alongside the device, nicotine format, flavour system and intended user experience.
Nicotine is an optional ingredient in e-liquid and is included when a product is intended to deliver a specified nicotine strength. Unlike VG and PG, which form much of the liquid base, nicotine is typically present in much smaller quantities.
The amount and form of nicotine used will depend on the type of e-liquid being developed. Two of the most common forms are freebase nicotine and nicotine salts, which have different formulation characteristics and can be suited to different product formats and nicotine strengths.
Nicotine concentration is usually expressed in milligrams per millilitre (mg/ml). For example, an e-liquid labelled as 10mg contains 10mg of nicotine per millilitre of liquid.
For manufacturers, nicotine isn't simply an ingredient that can be added independently of the rest of the formulation. Its concentration and form need to be considered alongside factors such as the VG/PG ratio, flavour system, intended device and finished product format.
In the UK, nicotine-containing e-liquids are also subject to specific regulatory requirements, meaning formulation decisions need to account for compliance as well as the intended characteristics of the product.
Flavourings give an e-liquid its intended flavour profile, but developing that profile involves more than simply choosing a flavour and adding it to a VG/PG base.
E-liquid formulations can use individual flavour components or combinations of concentrates to build a finished profile. The amount and combination used will depend on the intended flavour, the other ingredients in the formulation and how the finished product is designed to perform.
Building the Flavour Profile
A formulation may combine multiple flavour components to create the intended profile. Even apparently simple flavours can require several elements to achieve the desired balance, depth and character.
Balancing the Formulation
Flavourings need to work alongside VG, PG, nicotine and the wider formulation. Changes to one part of an e-liquid can affect how the finished flavour is perceived, so the formulation needs to be considered as a whole.
Consistency at Scale
For a commercial e-liquid, creating the desired flavour is only part of the process. The finished formulation also needs to be capable of being manufactured consistently from one production batch to the next.
For brands developing an e-liquid range, this means flavour development is both a creative and technical process. The objective isn't simply to produce something that tastes good during initial development, but to create a flavour system that works within the finished formulation and can be reproduced consistently during manufacture.
An e-liquid formulation is more than a list of individual ingredients. VG, PG, nicotine and flavourings need to work together as a complete system, with changes to one component potentially affecting the characteristics of the finished product.
Body & vapour
Contributes to the viscosity of the formulation and is commonly associated with greater vapour production.
Carrier & fluidity
Helps create a thinner formulation and acts as an effective carrier for flavourings and nicotine.
Strength & formulation
Where included, the nicotine form and concentration need to suit the intended product, formulation and use case.
Taste & character
Create the intended flavour profile and need to remain balanced with the other components of the formulation.
Changing one ingredient can influence the wider product.
Adjusting the VG/PG ratio, nicotine concentration or flavour system can alter characteristics elsewhere in the formulation. This is why commercial e-liquid development involves balancing the ingredients together rather than deciding on each one independently.
For a brand, the finished formulation therefore needs to be developed around the desired product characteristics, intended device and format, target nicotine strength and flavour profile.
The right formulation depends on much more than selecting individual ingredients. From VG/PG balance and nicotine format to flavour development and production requirements, each decision needs to support the intended finished product.
Own Label Creations works with brands to develop and manufacture e-liquids around their product requirements, from initial formulation and flavour development through to commercial production.
Our knowledge hub continues valuable insights and information about nicotine products and the nicotine industry. Take a look at some of our other articles to learn more.
