Abstract: Hot molds are internally cooled by providing a plurality of cooling passages having first and second opened ends, in the body of said molds; a plurality of blowing heads, each of which having an inner flow convertor defining an inner anular chamber and a central suctioning passage, and is coupled to the first end of a corresponding cooling passage, in order to provide a tangential flow of cooling air to said cooling passage causing a swirl cooling current therethrough, which is accelerated by an air current that is suctioned through the suctioning passage of the blowing head, and which afterwards is exhausted through the second end of said cooling passage; and cooling air feeding means correspondingly coupled to each of said blowing heads, providing a flow of cooling air to said blowing heads.