Vaping e-liquids are made up of four basic ingredients; water, nicotine, flavourings, and a mix of propylene glycol and vegetable glycerin base (most commonly known as PG and VG). PG and VG ratios will differ from e-liquid to e-liquid, depending on the type of consistency the manufacturer is trying to achieve.
If the VG content is higher than the 50%, it will be best used on sub-ohm devices, whereas if the PG concentration is at 50% or higher, a MTL device is suggested, as they are functioning at lower power, and the harshness of the e-liquid could be too much to bear into a Sub-Ohm device. An e-liquid with High PG concentration will be harsher than one with higher VG percentages, therefore this is why they have suggested type of devices.
Here is how they differ below: Propylene Glycol (PG): This is a lab-made liquid that the FDA generally views as safe in food, drugs, and cosmetics. It’s also used to make artificial smoke or fog for performances. It can irritate the lungs and eyes and maybe more harmful for people with chronic lung diseases like asthma and emphysema.
Vegetable Glycerine (VG): Vegetable glycerin, also known as glycerol or glycerine, is a clear liquid typically made from soybean, coconut, or palm oils. It is odorless and has a mild, sweet taste with a syrup-like consistency, and is particularly popular in the cosmetic industry along being utilised for several other uses.