Definition:

Updraft (adjective) refers to the air flow through a kiln as it is firing. In an updraft kiln, the air flows from a burner or firebox at the base of the kiln and exhausts out the top of the kiln.

Updraft (noun) is used by many potters as a shortened form of saying "updraft kiln". "Kiln" becomes the understood and unstated object of "updraft", converting it from an adjective into a noun.

Examples:

I'll be unloading the updraft kiln this evening. (adjective)

Are you firing the updraft next week?
(noun)