Glencraig was made in Lomond stills at Glenburgie. Lomond stills have a rectification column instead of a lyne arm and are akin to a cross between a traditional pot still and a column still.
The idea behind the Lomond stills that were introduced at Ballantine's distilleries (including Miltonduff and Scapa as well as Glenburgie) was to produce different types of whisky from the same still, including a lighter, versatile, fast-maturing whisky that would age quicker and be more attractive to the American market.
Glencraig was named after Ballantine's production director William Craig. The spirit was used exclusively for blending. The Lomond stills at Glenburgie were installed in 1958 by owners Ballantine's / Hiram Walker and produced Glencraig there until 1981, when they were pulled out and replaced with pot stills.
Glencraig was never released as an official bottling. However, a very small number of casks have been bottled by independent bottlers.