wherein each of the two pieces of the mold insert comprises at least one portion partly defining said mold cavity which is made of a material or a combination of materials, other than glass {HEAD ~ the thermal diffusivity} α of which fulfills {TAIL ~ the condition} 
wherein each of the two pieces of the mold insert comprises at least one portion partly defining said mold cavity which is made of a material or a combination of materials , other than glass { HEAD ~ the thermal diffusivity } α of which fulfills { TAIL ~ the condition }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL