Man that’s great. I don’t think its necessary at all and could be detrimental. When I was using stirrers I did this using heat and pretty high speed with an overhead stirrer. By leaving out the flavors I was attempting to thin the PG/ VG without injecting any air into the flavors. I did use a bearing device in a large canning jar and lid so to eliminate introduction of any new air. The point is that I was attempting to create a shearing effect with a blade stirrer and not have to be concerned about aeration. Nope, a blade is not going to create a shear effect and it did inject air into the PG?VG mix. Bad Idea…
I thought without nicotine and flavors no bad effects would occur. But I did not consider the effects of aerating PG. And yes I’ve gone on and on about oxidized nicotine in turn oxidizing flavors. Here’s what Satan aka DOW Chemical has to say:
Propylene glycols are hygroscopic liquids and efficient humectants. As such, they attract and hold water when exposed to the environment. Propylene glycols are sensitive to
oxidizing agents, e.g., the oxygen in air, especially when exposed to elevated temperatures and/or sunlight (ultraviolet light). Therefore, propylene glycols may degrade in the presence of air/oxygen, resulting in an increase of the acid content, color, ultraviolet light absorption, odor and a decrease of purity (assay)… Depending on the individual product and conditions,
various degradation products can be formed, such as aldehydes, ketones, acids and dioxolanes.
Study Conclusions: (theirs)
Propylene glycols are susceptible to sunlight (UV) catalyzed (partial) oxidation in the presence of air. Such partial degradation can negatively impact product quality, evidenced by increased acid, aldehyde, carbonyl and water contents, and product odor.