I have recently been cutting various PG-free glycerin-based e-liquids with glycerin and distilled water. Here is what I have found to help get the desired vaping experience when mixing/cutting the e-liquid:
Adding water: Reduces viscosity (thins) for better wicking, reduces throat hit much more than adding VG, reduces amount thickness and duration of vapor, also reduces amount of nicotine (usually not much, as amount of water added usually is small), reduces flavor
Adding VG: Primarily used to reduce amount of nicotine (and get more bang for your buck as VG is much cheaper than VG e-liquids w/nicotine), may increase vapor amount/thickness/duration if adding to liquid containing any water, reduces throat hit much less than adding water, reduces flavor
Adding flavored/unflavored VG-based liquid w/nicotine: Increases throat hit, increases nicotine hit, may increase or decrease vapor amount/duration/thickness depending on amount of water contained, increases flavor (if flavored liquid is used)
As you can see, these three work in a dynamic relationship that can be somewhat difficult to work out at first. If you are not happy with your vapor production for example, you may want to add some VG. If you are unhappy with the throat hit, then you probably need more nicotine, but an unsatisfactory throat hit could also be due to too much water. If there is too much water in the original liquid that you are cutting, then all you can do is add VG which will increase vapor, but delute the amount of nicotine, so you may not be able to get the throat hit you want. If you want more of a nicotine hit, throat hit, and vapor, then you need to get a higher strength e-liquid which also has less water and is thicker.
Personally, I don't want any throat hit, and I want a fair nicotine hit. I add enough VG to cut the nicotine just enough, then add water to reduce the throat hit, but yet not too much water to ruin the vapor production, as I still want a decent amount of vapor.
Adding water: Reduces viscosity (thins) for better wicking, reduces throat hit much more than adding VG, reduces amount thickness and duration of vapor, also reduces amount of nicotine (usually not much, as amount of water added usually is small), reduces flavor
Adding VG: Primarily used to reduce amount of nicotine (and get more bang for your buck as VG is much cheaper than VG e-liquids w/nicotine), may increase vapor amount/thickness/duration if adding to liquid containing any water, reduces throat hit much less than adding water, reduces flavor
Adding flavored/unflavored VG-based liquid w/nicotine: Increases throat hit, increases nicotine hit, may increase or decrease vapor amount/duration/thickness depending on amount of water contained, increases flavor (if flavored liquid is used)
As you can see, these three work in a dynamic relationship that can be somewhat difficult to work out at first. If you are not happy with your vapor production for example, you may want to add some VG. If you are unhappy with the throat hit, then you probably need more nicotine, but an unsatisfactory throat hit could also be due to too much water. If there is too much water in the original liquid that you are cutting, then all you can do is add VG which will increase vapor, but delute the amount of nicotine, so you may not be able to get the throat hit you want. If you want more of a nicotine hit, throat hit, and vapor, then you need to get a higher strength e-liquid which also has less water and is thicker.
Personally, I don't want any throat hit, and I want a fair nicotine hit. I add enough VG to cut the nicotine just enough, then add water to reduce the throat hit, but yet not too much water to ruin the vapor production, as I still want a decent amount of vapor.
