Propylene Glycol and Vegetable Glycerin
The attached chart displays some of the qualities of Propylene Glycol (PG) and Vegetable Glycerin (VG), the two major constituents by volume of e-juice. Many E-Juices are a mixture of both with nicotine and flavorings added. There are also juices that are predominantly PG or VG.
The chart shows PG at 100% on the left and VG at 100% on the right. In between are varying mixtures with half PG and half VG in the middle.
Throat Hit and Vapor Production
100% VG provides a high volume of vapor whereas 100% PG provides more of a sensation in the throat. In-between is some of each.
E-Liquid with a high percentage of VG will usually be thicker than those with a higher percentage of PG. The viscosity may effect how well the e-juice works with various equipment. Some vendors may use liquids other than PG to thin VG mixes.
Flavor and Sweetness
VG has it's own property imparting some sweetness. However, VG tends to mute the added flavorings. A higher amount of PG in the mix tends to deliver flavors better. Other sweet flavorings can be added to high PG mixes to increase sweetness.
Most vendors indicate the ratio of PG and VG they offer or allow selection when one orders. It seems the predominate form has PG indicated first. 80/20 PG/VG is a common ratio. Some, often those with higher VG in their mix, offer in the notation like 70/30 VG/PG. There can be quite a difference between 75/25 PG/VG and 75/25 VG/PG. Some high VG vendors will state the PG first. A ratio of 20/80 PG/VG is high VG. Make careful note of which protocol a vendor is using when placing an order. Note: Some vendors may use refer to their mixtures as All VG or similar when they use no PG. There may be other constituents in the mix other than PG that may make for a thinner blend. Typically there are no pure VG mixes as flavoring are usually not in a VG base.
There are many factors which lead to the pleasure found in an e-juice. The ratio of PG and VG is an important one. The pleasure found in differing ratios can vary from vaporer to vaporer. Different equipment may also vary in appropriateness for different mixtures. The added flavors and nicotine can also alter the pleasure found in the variety of PG/VG mixes.
Enjoy your voyage into understanding E-Juice!