Method of moulding and tempering glass articles

In a method of press moulding a glass article by feeding a gob of molten glass into an open mould, closing the mould to form the article to the required shape, opening the mould after forming the article, removing the article from the open mould when it has cooled to a desired condition, and then further cooling the article after removal from the mould, the improvement of reducing the time of moulding the article comprising:

• regulating the temperature of the mould and time of closure of the mould so that moulding to form the article to the required shape is complete while the moulded glass is in a state of thermal inhomogeneity such that the viscosity of the glass of the surface of the moulded article is at most 10.sup.10.5 poises and the viscosity of the glass at the center of the thickness of the article is at most 10.sup.8 poises and substantially less than that at its surface;
• opening the mould and rapidly transferring the article, while the surface viscosity and viscosity at the centre of thickness of the article are substantially different such that the article still has thermal inhomogeneity, directly into a cooling medium, avoiding forces which cause deformation of the shaped article during its transfer from the mould into the cooling medium, said transfer of the thermally inhomogeneous article being accomplished while the surface viscosity of the article is at least 10.sup.5.6 poises and at most 10.sup.10.5 poises and substantially greater than at its center of thickness;
• and
• regulating the heat transfer from the article to the cooling medium to cool the article rapidly to a temperature at which its surface viscosity is at least 10.sup.12.5 poises.