Polysorbate 20 (Tween)
Polysorbate 20, or “Tween”, is an emulsifying agent to help essential oils stay mixed with water.
$4.38 – $6.95
In general, one uses as much Tween as they do essential oil in a blend -- but we've found we could use much less than that if we don't mind shaking the bottle before we use it. It has an odd aroma that dissipates after a while - perhaps a day later we don't notice it at all.