{TAIL ~ The refining} of {HEAD ~ the vitrifiable materials} after melting comprises at least one step of subjecting them to subatmospheric pressure while centrifuging 
{ TAIL ~ The refining } of { HEAD ~ the vitrifiable materials } after melting comprises at least one step of subjecting them to subatmospheric pressure while centrifuging
TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH