Most people pick an e-liquid by flavor and nicotine strength and never read the rest of the label. Two other ingredients do most of the work, though: propylene glycol (PG) and vegetable glycerin (VG). Together they form the base of the liquid, and the proportion between them decides how thick the vapor is, how clearly the flavor comes through and how the draw feels in your throat. Flavorings and nicotine are mixed into that base to make a finished juice.
The two base liquids in brief
Both PG and VG have no smell, and both turn into vapor when a coil heats them. They look oily, yet neither one is an oil. Chemically they are classed as sugar alcohols, and each is also used in food products. Where they differ is in thickness, in taste and in the sensation they leave in the mouth and throat.
| Property | PG | VG |
|---|---|---|
| Full name | Propylene glycol | Vegetable glycerin |
| Consistency | Thin, runny | Thick |
| Taste | Carries flavorings well | Faintly sweet |
| Throat feel | Pronounced throat hit | Smoother |
| Vapor | Thin, discreet | Dense clouds |
Propylene glycol (PG)
PG is a clear liquid with no color or odor. It is thinner than VG and does a better job of carrying flavor. It is also the ingredient behind the “throat hit”, the catch at the back of the throat that people compare to drawing on a tobacco product.
Where else PG turns up
Plenty of household goods contain PG. Toothpaste and shampoo use it, as do baby wipes and makeup. Several kinds of pet food include it too, with the notable exception of cat food.
The antifreeze story
You may have heard that PG is “in antifreeze”. Antifreeze comes in two kinds. The toxic kind is made with ethylene glycol (EG), which is not an ingredient of vape juice. PG is what goes into the non-toxic kind made for food-processing machinery, where the equipment cannot be allowed to touch toxic substances.
What is and is not known
PG has been studied a good deal as a food additive. As something to inhale it has been studied very little, and the long-term effects of inhaling it are not established. More testing is needed before anyone can say what they are.
Cautions with high-PG liquids
- Cats: PG has been linked to Heinz body anemia in cats, which is why cat food leaves it out. Avoid vaping high-PG juice around them.
- Throat irritation: many users report that high-PG liquids irritate the throat. A sore throat, a dry mouth and feeling thirstier than usual are the commonly reported effects.
- Allergy: a PG allergy is uncommon, but a small number of cases have been documented. If you are new to vaping, watch for a rash or any other reaction that worries you.
Vegetable glycerin (VG)
VG is the other half of the base, and in most bottles it is the larger figure of the ratio. It is derived from vegetable oil. Its main job is to thicken the liquid, which explains why a juice made entirely with PG is so watery. VG tastes slightly sweet and gives a gentler throat hit than PG does. Sub-ohm devices are usually paired with VG-heavy liquid.
Where else VG turns up
VG is just as common around the house. In food it appears in sugar substitutes, in some sweets and baked goods (where it holds in moisture and keeps them fresh) and in various pet foods. In the bathroom cabinet you will find it in toothpaste and other dental products, soaps, hand and medicinal creams, deodorant, aftershave, bubble bath, hair mousse and makeup.
What is and is not known
As with PG, research on inhaling VG is limited, and its long-term effects would need more testing to pin down.
Cautions with high-VG liquids
- Allergy: people who are allergic to coconut oil or palm oil may react to VG.
- Coil life: thick, sweet liquid clogs coils sooner, so expect to replace them more often.
- Older atomizers: some atomizers, mostly older designs built around small coils, cannot wick high-VG juice at all. Finding the ratios your hardware accepts takes some trial and error.
- Dryness: VG can leave you with a dry mouth, a sore throat and more thirst. Drink more water, and take a break from vaping if you feel you need one.
Choosing a VG/PG ratio
New vapers often ask which juice they should buy. No single answer fits everybody, in the same way that nobody can name the one fruit all people like most. Start from what you want out of the device.
- Throat hit: for a firmer kick at the back of the throat, pick a higher share of PG. Combined with well-mixed nicotine, a high-PG liquid hits harder.
- Big clouds: cloud chasing means producing the largest, densest plumes you can, and there are even contests for it. A higher share of VG is the way to get there.
- Discreet vaping: a lot of public places discourage or ban vaping near crowds. Amusement parks, airports, subways and beaches often set aside designated areas for it, and bystanders rarely enjoy a cloud blown their way. A low-VG, high-PG liquid keeps the vapor thin.
- Smoothness: high VG gives a smooth draw and a thick cloud, though it can mute the flavor somewhat. Turning the wattage up usually brings the taste back. Go carefully, because too much power burns the coil, and dry hits and damaged tanks are no fun to deal with.
- Mixing your own: making juice at home lets you test ratios directly. Steeping a mix for longer often strengthens its flavor, particularly when VG is high. Many flavorings are made on a PG base, so try single flavors as well as blends. You can also vape an unflavored VG/PG base to judge the vapor on its own. A mix that turns out too thick can be thinned with a little water, but too much will ruin the coil and the juice.
Common ratios and the flavors they suit
70/30 VG/PG is among the ratios you will see most often. 50/50 and 60/40 are easy to find as well, and some liquids are made with VG alone or PG alone.
The ratio also changes how certain flavors come across:
- High PG: fruit, tobacco and beverage flavors such as coffee, tea and milk.
- High VG: custards, creams and other desserts, because the dense vapor resembles the texture of the dessert itself.
Every vaper wants something a little different, so try several ratios and flavors before settling on one.