§1.Molecular Properties & Purity

Propylene Glycol (1,2-Propanediol, C₃H₈O₂, E1520) and Vegetable Glycerin (Glycerol, C₃H₈O₃, E422) are the two dominant base ingredients in nearly all E-Liquids. Chemically, both are monovalent alcohols with a high affinity for water and polar flavor molecules thanks to their hydroxyl groups. The pharmaceutical and food-grade specification (Ph. Eur. / USP) requires a minimum purity of 99.5 %. Lower grades may contain residues such as ethylene oxide or diethylene glycol, which can promote health-hazardous byproducts during vaporization.

Glycerol crystallizes at room temperature into a white, highly viscous mass and is extremely hygroscopic due to its three hydroxyl groups — it absorbs atmospheric moisture, which affects the aging and cloudiness of liquid over weeks. Propylene Glycol, by contrast, is a colorless, clear liquid under standard conditions with a slightly sweet taste and significantly reduced hygroscopicity. Both substances are thermally stable up to approximately 230–260 °C; beyond that, decomposition products such as acrolein, formaldehyde, and acetaldehyde are formed. Modern vaporizers operate in the 150–280 °C range, where controlled vaporization limits these byproducts to trace amounts. The decisive factors are the combination of sufficient airflow, the correct amount of cotton, and well-defined coil geometry — only then does the thermodynamic equilibrium tip in favor of clean vaporization, and the purity of the bases can be fully leveraged.

§2.Viscosity & Wick Saturation Mechanics (Capillary Action)

Viscosity is the central parameter that determines how a liquid flows through capillary structures. Glycerol has a dynamic viscosity of about 1,412 mPa·s at 20 °C — making it roughly 25 times more viscous than Propylene Glycol, whose value under comparable conditions is only 56 mPa·s. Crucially, this relationship is exponentially temperature-dependent: While PG reacts to cooling in an almost linear fashion, VG viscosity rises disproportionately as ambient temperature drops. This physical property directly governs the Capillary Action in the wick channels of a coil. Capillary Action describes the ability of liquids to travel against gravity along fine pores and capillaries due to adhesive and cohesive forces. Too low a PG content means: the viscous VG base flows through the cotton too slowly, the vaporizer consumes more E-Liquid than is being replenished — the result is a Dry Hit, the overheated wick begins to char, and every puff introduces harmful substances into the vapor.

On the other hand, an excessively high PG ratio (e.g., a 30/70 mix in a high-powered DL Vaporizer) can lead to gurgling and leaking. PG flows in so quickly that excess liquid exits through the air channels and causes bubble formation there. Practically speaking: The compression of the cotton, the bore diameter of the juice ports, and the capillary force of the wick material used must be in the right proportion to the base's viscosity. A rule-of-thumb orientation: The smaller the capillaries and the lower the power, the higher the PG content needs to be — and conversely, for large, highly porous wicks in RDA systems, Max VG can guarantee optimal wick saturation as long as a liquid-guided system is in place.

§3.Vapor Volume vs. Flavor Carrier Dynamics

Propylene Glycol functions as the polar carrier medium par excellence. Due to its low surface tension and intermediate polarity, PG forms thermodynamically stable mixtures with aromatic compounds and transports flavor molecules directly into the airways. Chemical flavors with a polar character (fruits, menthol, and sweetener compounds) bind particularly efficiently to PG molecules, resulting in a sharply articulated flavor profile with high intensity and a clean attack. PG also handles thermal conduction to the wick and vaporizes at a lower temperature (boiling point around 186 °C), meaning maximum vapor production is reached at lower coil temperatures.

Glycerol, by contrast, has a significantly higher boiling point (290 °C) and requires more energy to transition into the gas phase. In return, it delivers dense, snow-white aerosol clouds upon vaporization: the larger glycerol droplets in the mist refract and scatter light more strongly, creating the characteristic milky appearance. Glycerol also has a natural, subtle sweetness (about 60 % of the sweetness of sucrose) that harmoniously complements sugar substitutes in flavors — or, depending on the ratio, floods the flavor profile with unwanted sweetness. Critically, higher VG ratios partially dampen flavor perception, since the larger, heavier glycerol molecules associate less effectively with volatile flavor compounds. Practical consequence: for 70/30 and 80/20 bases, you need 2–5 % higher flavor concentrate to achieve the same flavor impression in the finished liquid as in a 50/50 mix. This DIY correction is essential for reproducible flavor profiles.

§4.VG/PG Ratio Matrix 2026

Choosing the VG/PG ratio is the decisive lever for controlling vapor volume, flavor, throat hit, and flow behavior of your liquid. The following matrix summarizes the five most common mixtures along with their precise thermodynamic and sensory properties — orient yourself primarily around your hardware, since the coil geometry determines the boundaries within which a liquid will function safely.

§5.Throat Hit & PG Sensitivity

The Throat Hit — that tingling, sometimes irritating sensation in the throat upon inhalation — is primarily induced by Propylene Glycol. PG reacts with mucous membrane receptors in the throat and trachea much like menthol or spicy seasonings do, triggering an intense scratching sensation. The higher the PG ratio in the liquid, the more pronounced this effect becomes. For switchers from conventional cigarettes, this effect is positive, since it simulates the sensory feedback they are accustomed to from classic nicotine intake. At higher PG concentrations and especially over extended vaping sessions, however, the substance can cause noticeable dryness in the throat.

Typical signs of PG sensitivity include: a persistent dry throat, an increased tickling cough with every puff, a feeling of tightness in the chest, extremely dry lips, up to mild swelling of the throat. In rare cases, a type of contact allergy appears with facial itching, watering eyes, or mild shortness of breath. Those affected should gradually reduce their PG content and monitor whether symptoms subside.

As an alternative, High-VG mixtures (80/20 up to 100 % VG) are available, since glycerol is far more tolerable for mucous membranes and does not cause such intense irritation. The downside: less throat hit and a somewhat muted flavor profile. For purists, there is also Bio-PG (1,3-Propanediol), a nature-identical variant derived from rapeseed oil that is often considered even better tolerated. Practically: anyone who reacts to too much PG benefits immediately from switching to 70/30 or 80/20 — a simple self-treatment trial before consulting a doctor. Halve the PG content first and observe for 3–5 days. If the airways relax noticeably, PG concentration is confirmed as the trigger.

§6.Thermodynamics & Winter Vaping

The viscosity of liquids is, from a physical standpoint, an exponential function of temperature. For Glycerol, this relationship is especially striking: at room temperature (20 °C), the dynamic viscosity is around 1,412 mPa·s — once cooled to 0 °C, this value roughly doubles, while at –10 °C the base becomes extremely viscous and nearly gel-like. This change follows Arrhenius kinetics: as temperature drops, the kinetic energy of the molecules decreases, the intermolecular hydrogen bonds between the three hydroxyl groups of the glycerol molecules become more stable, and internal friction resistance rises.

The practical consequence for outdoor vapers: a 70/30 liquid that flows flawlessly through a Sub-Ohm prebuilt coil at 20 °C can overwhelm the capillary capacity of the wick in sub-zero winter temperatures. The consequence is Dry Hits after just a few puffs, since the coil overheats before the viscous base can be replenished. This often causes irreversible mechanical damage to the cotton — the wick chars permanently, and the coil must be replaced.

The solution lies in a seasonal switch to 50/50 or 60/40 bases. These mixtures lose far less flowability in the cold and guarantee safe wick saturation down into the slightly sub-zero range. Another tip: in winter, store the device in an inner pocket (around 20–30 °C) and take a few warm-up puffs before the first draw outdoors, so the base can heat up inside the coil. Using a battery sleeve with an insulating layer can also help, since cold affects not only the base but also the battery.

§7.Buying Advice & Base Recommendations

For targeted DIY mixing, it is worthwhile to purchase pre-made bases at the right concentration — especially in the Nicotine Shots category, there are now VG-heavy and PG-heavy variants that allow precise control of the mixing ratio.

Editorial Recommendation: When in doubt, always start with the lower VG ratio and increase it gradually — this is how you avoid costly coil damage. All of our bases meet the Ph. Eur. quality standard and are precisely labeled with their mixing ratios.

§8.Frequently Asked Questions