How the volume in a pot still affects reflux (and influences flavour)
The size of a pot still affects reflux simply because it determines the volume of liquid that constitutes a fill or “charge”. The amount of liquid inside controls the distance a compound must travel to become part of the distillate. And the physics of that is important.
A smaller fill increases the distance – and energy – required for vapours to reach the condenser, creating the opportunity for more reflux to occur inside the still. A larger fill, in contrast, reduces the opportunity for reflux to occur as there is simply less space and energy required to push gaseous compounds over into the condenser.
The amount of reflux activity within a still massively affects the flavours and aromas in the new spirit. More reflux leads to a lighter and more refined new make spirit, while less reflux leads to a heavier, oilier and denser new make spirit.
Looking to refresh your reflux knowledge? Read this: What is reflux and how does it influence Scotch whisky character?