Propylene Glycol is a carrier fluid used to hold the flavour in E-Liquid. It is tasteless, odorless and found in everyday products such as food, medical vaccines, cosmetics, medicine, hand lotions, shampoos, theater fog and cleaning supplies. PG allows the E-Liquid to be vaporised by the atomiser, producing the vapor that is inhaled into the lungs.
Vegetable Glycerin is a carrier fluid used to hold the flavour in E-Liquid. It is odorless and commonly used in the food and cosmetic industry. Vegetable Glycerin is an organic compound produced from vegetable oil. VG allows E-Liquid to be vaporised by the atomiser, producing the vapor that is inhaled into the lungs.
VG is classed as a carbohydrate for food purposes. VG is hypoallergenic, and is found in hypoallergenic soaps, cosmetics and other products. VG naturally has a sweet taste, and though it is a carbohydrate, it does not have a drastic effect on blood sugar and can be safely used by those who require insulin.
Both Propylene Glycol and Vegetable Glycerin are carrier fluids that hold the flavour in E-Liquid and are both odorless and tasteless. PG is thinner than VG and is more easily vaporised by the atomiser.
PG provides a stronger "throat hit" and more effectively carries the flavour during vaping. VG is a more viscous liquid which has a slightly sweet taste; it is used in foods for this purpose. In addition, it produces more vapor than PG.
Yes, your E-Liquid is still safe to use, even after the colour change. E-Liquids change colour due to oxygenation, extreme temperature changes or exposure to sunlight. This is a harmless process that does not effect the safety, vape-ability or quality of the product.