a "vigreux column", named after the french glass blower (1869–1951), is a type of air condenser in which a glass blower has modified the simple tube to include an abundance of downward-pointing indentations, thus dramatically increasing the surface area per unit length of the condenser; the vigreux column was invented in 1904. such columns are often used to add the theoretical plates required in fractional distillation, and present added cost for their manufacture, which can include designs with or without an outer glass cylinder (jacket), open to air or allowing fluid circulation, or, to aid in insulation, an outer vacuum jacket.