Propylene glycol is one of the world’s most useful chemicals. It’s an emulsifier that keeps the ingredients in a solution mixed. Because it attracts and retains moisture, it can help to prevent a product from drying out. Propylene glycol is also antimicrobial, so it helps to keep products from spoiling. Some of the products that commonly include propylene glycol include moisturizers and lotions, medications, deodorants, shampoos and cosmetics. Propylene glycol is also used in the fluid for commercial smoke machines, which might be the reason why it has been used as the primary component of e-liquid since the days of the first e-cigarettes.
In terms of how they perform in an e-liquid, the primary differences between propylene glycol and vegetable glycerine are that propylene glycol is thinner and generates a slightly scratchier sensation in the throat when it’s inhaled. With that in mind, you can expect a high-PG e-liquid to produce smaller vapour clouds and to give you a stronger throat hit. The smallest vaping devices work best with high-PG e-liquids because a device with a very small atomizer coil needs a thin vape juice in order to work reliably.