Dipropylene Glycol (DPG) is the most common diluent and solubiliser in perfumery today. It is sometimes used to pad out a formula (bringing its total to 1,000 for uniformity) and it can offer some minor benefits as a fixative, but an intelligent combination of musks is usually a better option for that purpose. DPG is almost odourless — in general it has a very faint almost alcohol-like odour that some only some people can perceive. Unlike alcohol, however, it is non-flammable having a closed cup flash point of 138°C (280°F). It has a higher viscosity than water. Some fragrances contain very large amounts of DPG to lower their cost or even their strength as we see in Baccarat Rouge 540 which uses nearly 50% in the finished formula for Eau de Parfum (compared to almost none in the Extrait). DPG is not readily soluble in fixed oils such as Fractionated Coconut Oil and can cause turbidity. If you are working with fixed oils a better option is ethanol or IPM (MIP). When DPG passes its expiry (usually after three or four years) it can develop an unpleasant bready-sour note. This can make it unsuitable for some long-term dilution needs. TEC, DEP and IPM are potential alternative options for those cases. NOTE: This must not be used in food or vape juices. Dipropylene Glycol is not a safe alternative to Propylene Glycol. Do not consume.
