In the spirit of a useful scientific comparrison, (I'm out of work and bored so i'm just gonna have fun with this) ^ that by itself is interesting but inconclusive.
Two tests come to mind. 1st is your pure VG vs PG question. 2nd is a complete recipe (any typical e-liquid). Let's leave number 2 alone for now and look at your original concern.
Only comparing "raw" VG/PG evaporation vs residue while a good start, is incomplete in giving us a useful conclusion. Are the properties of VG/PG changed in the vape process?
Vapor is essentially steam but (but since this is not 100% water) also carries other "contaminants" (i.e. everything in PG/VG that are suspended solids after flash evaporation). When it cools off it recondenses to liquid form.
In the case of a vapor cloud blown out and lingering in a room, some of this is absorbed into the atmoshphere prior to condensation (and carry some suspended particle with it), and some get physically deposited in/on its surroundings after condensation.
In the case of what we vape into our lungs, everything that is not expelled when we exhale is deposited in our lungs. Our lungs are designed to capture the air (or vapor) that we breath including any suspended solids that are with it.
I'm stating the obvious but for a reason. The next experiment in my mind would be to compare the difference between the contents of vaporized VG/PG prior to inhalation vs post exhalation. Without a lab to accurately analyse both we are at a loss, but there is more we can do.
One test you can do though to further your original one: Prevaporized liquid vs post vaporized liquid evaporation and residue.
Test apparatus: Build a simple see through plastic box (any clear sheet plastic) glued and sealed on all sides and bottom but leaving the top free to be removed for inspection later. I would imagine about one cubic foot in volume. Find a grommet at your local hardware store who's inside diameter will snugly hold your favorite 2 piece auto battery e-cig. Drill a hole in the side/end of the box to insert your grommet. On the opposite end of the box drill a hole about 1/2" to 1" in diameter and cover with a folded paper towel and tape in place, (this is your filter for make up air).
To get fancy, build 2, one for each VG and PG test to compare side by side after all that was your original observation.
Tape your box lid down with electrical tape (it won't leave residue and will seal for your purpose). Charge up a battery and refill a carto, and slip your PV into the grommet "mouth" end inside. (Here's the reason for an auto battery) blow on the battery sticking out of the box and fill the box with vapor. If you see vapor coming out of the filter end then slow down or stop temorarily, Blow the whole cart till it is done into the box over as little time as possible.
Obsevations:
1. Over the course of vaping into the box is there a noticable buildup/condensation layer on the surface of the box?
2. Waiting for a period of time sufficient for "the air to clear" have the conditions in Q1 changed?
3. If a noticable layer is present, is it solidified? Or is it liquid?
4. Remove the filter and inspect; findings?
5. If liquid residue is present allow a reasonable time to elapse to allow evaporation of deposited substance.
6. Repeat test until satisfied with presence or absence of findings.
Clean one of the test boxes out and instead of just testing pure VG/PG you can now test your fav e-juice and record results (there are more suspended particles in the full recipe) Compare results with test of VG only and PG only and record observations.
All of this represents the next step to your pre-vaporized static evaporation vs residue test, with a post vaporized but pre inhaled test. Next text would be to put the PV into your mouth instead of the box and exhale into the box in order to compare/discern what our body retains.
In the spirit of your original concern (even though i'm 1/2 just having fun with this) there is more that you can do to validate or disqualify your concerns if you are up to it. Not as conclusive as if you had a lab on standby ready to perform Gas Chronomograph analysis of the box and filter surfaces to give you an exact list of remaining contaminants, but you can have a bigger view of the picture than is possible from only your first experiment.
Peace, eHuman
Also worried about flavorings and colorants
Maybe I will go back to PG
