Okay ....
Without looking at all the flavors and what not...
Basic chemistry 101
Water and oil don't mix...
No there's no "oil " per say but here is a trick that can be applied to any compounding:
This can happen to any e-liquid you make when one of the components does not mix with the others.
Most if not all flavors will mix properly with PG, but not with VG, so here is what you do:
Mix all ingredients less you VG and thoroughly mix, 99% of the time there will be no issues, then add your VG last. If your NIC is VG based this applies too, do not add it until after you have combined all the other ingredients.
The problem occurs from the water in the VG and certain components that naturally will not combine together. like gasoline and water! If you add alcohol into the gasoline, it will bond with the water and make what's called a
soluble solution and now the water will mix with the gasoline!
Likewise in e-liquids the same principal applies; you can also mix all components and figure in about 3-5% PGA which will help the ingredients to mix, then lastly add your VG', TADA!
No Clouds or mixture separation! (emphasis mine; IDJoel)