Esteban.......The color of the getter deposit and its density are a product of barium atoms evaporating and absorbing any remaining gas in a tube once the vacuum has been sealed and flashed. You will see silver getters and even black getters depending on how fast flashing is done. That the getter deposit may be less dense on one tube than another or less dense in an area around the inside top of a tube than another area is not an indicator of a problem. If the silver, grey or black colored getter changes color to white you have a gas leak and the tube needs to be replaced immediately. Other than that, I would not be concerned about how the tube appears in the dark. If you are in doubt as to the electrical performance of a tube have it tested for gas, shorts, plate current, and transconductance.
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Dan
STUDIO - McIntosh C1000C/P, MC2301 (2), MR88, Aurender N10, Esoteric K-01X, Shunyata Sigma spdif digital cable, Sonos Connect, PurePower 2000, Stillpoints, Furutech Flux 50, Michell Gyro SE, Michell HR Power Supply, SME 309, Ortofon Cadenza Black, Wireworld, Sonus faber Amati Anniversario
LIVING ROOM - McIntosh C2300, MC75 (2), MR85, Magnum Dynalab 205, Simaudio MOON Neo 260D-T, Schiit Audio Yggdrasil, Aurender N100H, Shunyata Sigma USB cable, Micro Seiki DD40, Ortofon Cadenza Blue, Nakamichi BX-300, Sony 60ES DAT, PS Audio P10, Furutech Flux 50, Sonos Connect, Stillpoints, Wireworld, Kimber, PMC EB1i, JL Audio f113
VINTAGE - McIntosh MA230, Tandberg 3011A tuner, Olive 04HD, Sony DTC-59ES DAT, McIntosh 4300V, JBL 4312A
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