Released in February 1969, this National Film Unit documentary offers an impressionistic view on the making of sheet glass. Director Lynton Diggle follows the raw materials (sand, limestone, dolomite) to a Whangarei factory, where they’re combined with broken glass. There, men in protective gear look like they’re enacting an alchemical ritual, as the ‘frit’ mixture is melted in the “punishing heat” of a crucible. Then it’s transferred to the drawing chamber where a toffee-like wall of glass is pulled up for cooling and slicing. Ambient sounds are used to forge a percussive score.