PG (Propylene Glycol) – What It Is & Why It Matters in Vaping

Definition

PG (Propylene Glycol) is a clear, slightly sweet liquid that forms one half of most VapeJuice“>vape juice. It carries flavour better than Glycerin)”>VG (Vegetable Glycerin), gives the familiar “Hit“>throat hit” that smokers enjoy, and keeps ingredients from separating. In short, PG is the flavour-bringer and sensation-maker in your e-liquid, working alongside VG to balance vapour, taste, and wicking speed in everything from tiny pod systems to high-wattage box mods.

Technical Details

Propylene Glycol is a synthetic organic compound (C₃H₈O₂) with a low viscosity of ~42 mPa·s at 25 °C, making it far thinner than VG. This low thickness allows it to saturate small cotton wicks quickly and prevents dry hits in pod systems or high-puff count disposables. E-liquids are blended with PG anywhere from 30 % to 70 %; 50/50 PG/VG is the default for mouth-to-lung (MTL) kits, while 30/70 is common for direct-lung clouds. Pharmaceutical-grade USP or EP PG is used to ensure purity; lower grades may contain impurities that clog coils or irritate airways. PG boils at 188 °C, well within the range of most power mode devices, and has a water-activity value that helps prevent microbial growth in open bottles.

Usage & Tips

  • For beginners: Start with 50/50 PG/VG liquids in low-wattage pod systems to get a satisfying throat hit without leaking.
  • Preventing leaks: High-PG liquids can oversaturate loose cotton; close airflow when refilling and store tanks upright.
  • Allergy watch: A small percentage of vapers experience dry mouth or rashes; if symptoms appear, switch to higher-VG blends and consult a pharmacist.
  • Coil life: PG is less gunk-forming than VG, but sweeteners still caramelise; rinse coils weekly and pass-through charge only when necessary to avoid overheating the liquid.

History & Context

PG entered the vape scene in 2004 when early cig-a-likes needed a fast-wicking base that mimicked cigarette draw. Its pharmaceutical pedigree—already used in asthma inhalers—helped legitimise vaping among regulators and medical circles in Australia and worldwide.

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