Introduction to the Glass and Screen Aqeinq Procedures This procedure is broken down into three subsections. They are: I. Glass Ageing This procedure tests the ageing properties of CRT glass alone@ independent of screening conditions or phosphors. II. Pre-Ageing This procedure tests the often rapid initial ageing of the complete CRT system. This test may be used alone or as a pre-test before long term ageing. III. Long Term Ageing This procedure tests the long term ageing Properties Of the complete CRT system. If the tube is cut down after the test is complete@ glass and screen effects may be seperated.