Not a chemist so looking for a little clarification. The typical "base liquids" (that nicotine is suspended in) are vegetable glycerin ("VG") and propylene glycol ("PG"). When you say "glycerol", which exactly are you referring to? (Or is it both?)

(VG makes the larger "clouds" that some people prefer, typically with lower nicotine concentrations. PG is much less visible and dissipates quicker, but some people consider it a little more harsh, regardless of nicotine concentration)