The liquid used in vaporizers, known as e-liquid or vape juice, is composed of flavorings, nicotine (optional), and a carrier base. Propylene Glycol (PG) is one of the two main ingredients in this carrier base. It plays a fundamental role in creating the vapor and delivering the desired experience. Understanding what PG is helps explain how e-liquids function.
Defining Propylene Glycol
Propylene Glycol is a synthetic organic compound (C₃H₈O₂). It is a clear, odorless, and nearly tasteless liquid at room temperature. It belongs to the alcohol family and is known for its ability to absorb water and mix completely with other solvents. PG is used widely across various industries for its solvent, preservative, and moisture-retaining (humectant) properties.
The U.S. Food and Drug Administration (FDA) classifies PG as “Generally Recognized As Safe” (GRAS) for use as a food additive. This allows its use in food colorings, flavorings, and medications, where it helps dissolve and carry ingredients. PG is also commonly found in cosmetics, pharmaceuticals, and theatrical fog machines. Note that the GRAS status applies to ingestion, which differs from repeated inhalation over time.
The Role of PG in E-Liquids
Within the e-liquid formula, Propylene Glycol acts primarily as an efficient solvent and a vapor-producing agent. PG’s low viscosity makes it a highly effective carrier for nicotine and flavor concentrates. It ensures flavorings dissolve uniformly and are delivered effectively in the vapor, resulting in a more pronounced taste in high-PG e-liquids.
PG is also responsible for the “throat hit,” a subtle scratchiness at the back of the throat sought by many former traditional cigarette smokers. E-liquids with a higher concentration of PG provide a more noticeable throat hit, mimicking the sensory experience of smoking tobacco.
PG produces a thinner, less dense vapor cloud compared to the other main e-liquid component. Its low viscosity allows it to absorb quickly into the atomizer’s wick and vaporize at lower temperatures. Devices with smaller coils, such as those used for mouth-to-lung (MTL) vaping, rely on this property to function efficiently and avoid dry or burnt tastes.
PG vs. VG Understanding the Key Differences
PG is almost always paired with Vegetable Glycerin (VG); the ratio between the two dictates the overall vaping experience. VG is a natural compound derived from vegetable oils, possessing a much thicker consistency than the thin, watery PG. This difference in viscosity is the fundamental distinction between the two components.
PG is superior at carrying flavor, resulting in a more intense and true-to-label taste experience. VG, in contrast, has a slightly sweet taste and is a less effective flavor carrier, often resulting in a milder flavor profile. Vapers who prioritize a strong, clean flavor generally prefer a higher PG ratio.
The compounds differ significantly in the vapor they produce. High-VG e-liquids generate large, dense clouds of vapor, making them the choice for cloud-chasing enthusiasts. Conversely, higher PG e-liquids produce less voluminous, thinner vapor, which is favored when discreetness is desired.
PG provides the desired “throat hit,” while VG offers a much smoother sensation on the inhale. The PG/VG ratio is usually displayed on e-liquid bottles, with common ratios like 50/50, 70/30, or 30/70. A balanced 50/50 ratio offers a middle ground of throat hit, flavor, and vapor production, and works well in most standard devices.
Higher PG blends, such as 60/40 or 70/30 (PG/VG), are best suited for lower-wattage, mouth-to-lung devices because the thinner liquid wicks easily. High-VG e-liquids, such as 70/30 or 80/20 (VG/PG), are necessary for high-powered, sub-ohm devices. The thickness of high-VG liquid requires more power to vaporize effectively, producing the thick clouds those devices are designed for.