Implosion protection thumb|Datapoint 1500 terminal with exposed chassis, with its CRT suffering from a "cataract" due to aging PVA Early CRTs had a glass plate over the screen that was bonded to it using glue, creating a laminated glass screen: initially the glue was polyvinyl acetate (PVA), while later versions such as the LG Flatron used a resin, perhaps a UV-curable resin. The PVA degrades over time creating a "cataract", a ring of degraded glue around the edges of the CRT that does not allow light from the screen to pass through. Later CRTs instead use a tensioned metal rim band mounted around the perimeter that also provides mounting points for the CRT to be mounted to a housing. In a 19-inch CRT, the tensile stress in the rim band is 70 kg/cm2.
Implosion protection thumb|Datapoint 1500 terminal with exposed chassis, with its CRT suffering from a "cataract" due to aging PVA Early CRTs had a glass plate over the screen that was bonded to it using glue, creating a laminated glass screen initially the glue was polyvinyl acetate (PVA), while later versions such as the LG Flatron used a resin, perhaps a UV-curable resin The PVA degrades over time creating a "cataract", a ring of degraded glue around the edges of the CRT that does not allow light from the screen to pass through. Later CRTs instead use a tensioned metal rim band mounted around the perimeter that also provides mounting points for the CRT to be mounted to a housing. In a 19-inch CRT the tensile stress in the rim band is 70 kg/cm2.