The helmet on a whiskey still

[Maschmeier]

I am trying to find information on the helmets of whiskey stills. What are people's opinions of putting a helmet above the boiler on a reflux still when making whiskey? What kind of helmet dimensions do people like and what is the difference in diameter between the equator of the helmet and the entrance/exit of the helmet. Thanks!

[Mash]

What's a helmet? Other than the obvious.

[Swede]

The ogee or onion? It's usually there to give a small amount of passive reflux, and to guide vapor flow to the lyne arm. The amount of reflux generated is usually a combination of several factors including the ogee, any passive airflow that may cool it, and the heat input into the boiler.

[bluestar]

The helmet is something of an exaggerated onion/ogee, which Swede has reasonably characterized. Generally, I think of the helmet (see Kothe's "Exclusive" pot still for an example) more like the onion on a portuguese alembic still, than the ogee on a whiskey or plate still. Compared to the alembic, it has a much larger surface area for reflux compared to the surface area of the boil, and a more restricted waist, that would encourage expansion of the vapors as they enter the helmet and increased reflux. Enough reflux might reduce the need for a dephlegmator in a whiskey still, for example. It functions similarly but I suspect more efficiently than the extended conicals with ogee before going into a swans neck lyne arm, as typical of some traditional whiskey and gin stills.