Glass evacuated tube Technique specification Material:borosilicate glass according to ISO3585:1991;transmittance of borosilicate glass:0.92.Absorbance of solar selective absorptive coating:0.94;Hemispherical emittance:0.08;Getter according to GB/T9505-1998. Start-up temperature:no more than 25. Start-up time:no longer than 2 minutes under normal sunshine. Low temperature resistance:no breaks at-30 Heat impact resistance:no damages after over 3 timesalternative impacts of cold water below 25 and hot water over 90. Pressure resistance:cam withstand 0.6Mpa. Hail resistance:no damage by the impact of Φ25mm hail. Appearance standard:the color of the selective absorptive coatings should be even,and the coatings should have no wrinkles and peelings.The allowed tolerance of borosilicate glad tubes diameter should be in accordance with ISO4803:1978.camber of the borosilicate glass tube should be no more than 0.3%. The translation the borosilicate glass tube,which is 40-60mm away from flange end,should be round.The ratio of the longest to the shortest radial dimensions of the borosilicate glass tube should be no more than 1.02.