Abstract: The cooling of glass forming molds is accomplished by providing a plurality of radially spaced passages either in the mold itself or in a mold holder in good heat transfer relationship to a mold insert. The passages extend vertically and may either be completely through the mold or may extend substantially to the lower end of the mold. These passages are radially insulated by the compaction of a particulate material such as 316-L Stainless Steel Compacting Powder, with the compressed material being carefully packed within the passage and in surrounding relationship to a coaxially positioned metal tube. The metal tube provides access for the circulation of a liquid coolant. The thickness of the particular material, its degree of compression and its composition and the relative position thereof with respect to cavities of the glass forming mold, will determine the heat flow characteristics of the mold and/or mold holder.