Vegetable Glycerin (VG)
Vegetable Glycerin (or VG) is a colourless, viscous and odourless liquid found in the composition of e-liquids. It is one of the two major components along with Propylene Glycol (or PG) that constitute the neutral base for the production of these same e-liquids. It is a key factor in the production of vapour and limits the sensation in the throat called "hit". Its boiling temperature is 290 ° C but from 60 ° C it evaporates in the form of the cloud that we know and delighted vapoteurs and especially fans of "Cloud Chasing. Most manufacturers offer equal proportions of vegetable glycerine and propylene glycol in their recipes, we speak of 50PG / 50VG.
The vegetable glycerine used in most e-liquids is composed of glycerol up to 99.5%. For this reason, it is often said that vegetable glycerin and glycerol are identical. To be completely accurate, it is better to say that glycerol is the main molecule of glycerin.
The vegetable glycerin recommended by the AFNOR XP D-300-2 standard is a distilled glycerin of pharmaceutical grade USP (United States Pharmacopeia) and EP (European Pharmacopoeia) which contains at least 99.5% glycerol.
Vegetable glycerine used in pharmaceutical grade e-liquids can be edible if accompanied by a certificate of alimentarity.
Is glycerine always of vegetable origin?
There is vegetable glycerine, used in the composition of e-liquids, but also glycerine of animal origin.
What is glycerine used for?
Glycerine is widely used in many industrial and consumer products such as soap, detergents, medicines, cosmetics, food, drinks, paints, resins and paper.
Glycerine is mainly used in the pharmaceutical industry, especially as a carrier for antibiotics, antiseptics or in capsules. This molecule is found in cough syrups (expectorant) for example, but also in suppositories. It is a moisturising agent that improves the smoothness and lubrication of pharmaceutical preparations.
Glycerine is an excellent solvent for a wide range of active ingredients and chemical compounds.
Glycerine is also widely used in the cosmetic industry. It is the main ingredient in toothpastes. It is also widely used in skin care products (soaps, moisturisers) and hair care products (shampoos). The main qualities provided by this substance are softness, but also hydration.
Glycerine is also present in animal and human food. It is often used as a food carrier for liquid flavours, but also as a sweetener, emulsifier, thickening agent or preservative. It is also often incorporated into the extraction process of plant substances.
Airborne toxicity has been studied in rats. The only effect observed is a thickening of the tracheal mucosa following high-dose exposure, which is a form of protection against chemical irritants (Renne et al, 1992).
The NOEL (non-observed effect level) in rats by inhalation is 167 mg/m3 (Renne et al, 1992); it is from this type of data that occupational exposure limit values are calculated.
The concentration of blood glycerine measured in rats exposed by inhalation to a PG/VG mixture is not increased, which can be explained by the greater presence of endogenous than exogenous glycerol and/or rapid metabolism of glycerol after absorption.
Glycerol supplied from the external environment does not affect the concentration of glycerol produced by the body.
In gavage studies in rats, mice and rabbits, no maternal toxicity and no embryotoxic or fetotoxic effects were observed (OECD SIDS 2002).
Glycerol is also not carcinogenic or mutagenic (OECD SIUDS, 2002.).
In medicines used as an excipient according to the recommendations of the French Health Products Safety Agency of 2008, if the threshold is >10g, the Information to be mentioned in the special warnings and precautions for use is as follows: "This medicine contains glycerol and may cause headaches and digestive disorders (diarrhoea).
What is the role of vegetable glycerine in vaping?
Vegetable glycerine is a humectant and hygroscopic agent used increasingly thanks to the evolution of vaping equipment.
This hygroscopic element, which can contain up to a quarter of its volume in water, provides a nice aerosol density. Glycerine vaporises at 290°C, and is almost 3 times more viscous at room temperature (20°C) than mono-propylene glycol.
Its relatively high boiling point and high dynamic viscosity have made it a demanding diluent for vaporisation systems in terms of heating power and wick feeding capacity to avoid any dry hit.
Similarly, glycerol has the disadvantage of clogging the resistors. The higher the level of vegetable glycerine, the more often the resistors will have to be changed. Similarly, it will be necessary to carry out more frequent maintenance of the equipment.
Its humectant and hygroscopic properties make it a diluent of choice for vapers with sensitive throats or cloud chasers.
In its gaseous state, it condenses into fine droplets (usually in the presence of an air flow) thus trapping some of the neighbouring molecules (i.e. nicotine, aromatic molecules, water, etc.). This rapid phenomenon produces an aerosol that visually mimics smoke.