“…In previous papers (Cabric & Janicijevic, 2007;Cabric & Danilovic, 2009), we have described a design for an air cooler in a laboratory tube furnace, with the aim of regulating the crystallization rates in a column of crucibles and Tamman test tubes. In this paper, the development and improvement of the exterior and interior of the cooler, including an air-cooled tube with mounting rings, cold plugs, movable cold thresholds and slide bars ('crystallization incubator'), is presented (Fig.…”