i found a F40T12 tube in someones trash on the side of the road and brought it home lmao and i found it to be mercury starved, it glowed very very dim with stritations, so i thought im going to put it on my F96T12/HO ballast to kill it, to my surprise it ran fine it was dim but gradually got brighter, i flipped the orientation of the tube ever once and awhile so i didint burn out a cathode and eventually it was at full brighness and so i left it for about 20 min to cool down and i put it in my living room light (2x F40T12 fuxture) and it ran perfectly! no stritations or anything it ran normally! it is now in service in my living room XD

hows that work? why does it act dead then come back?

i have no idea

i found a F40T12 tube in someones trash on the side of the road and brought it home lmao and i found it to be mercury starved, it glowed very very dim with stritations, so i thought im going to put it on my F96T12/HO ballast to kill it, to my surprise it ran fine it was dim but gradually got brighter, i flipped the orientation of the tube ever once and awhile so i didint burn out a cathode and eventually it was at full brighness and so i left it for about 20 min to cool down and i put it in my living room light (2x F40T12 fuxture) and it ran perfectly! no stritations or anything it ran normally! it is now in service in my living room XD

The only reason I thought for this situation, is because mercury hasn't yet released from the capsule/amalgam, during the manufacturing stage. I think you could also run it on your F40T12 and wait several tens of mins, and the mercury would eventually evaporate and the lamp become stable.

This is quite common when the tubes are operated very rarely, getting old and stay in cold environment. The mercury then condenses on different parts (practically all metals tend to attract it there), so when powered up after long time, there is insufficient mercury in the gaseous form before the tube warms up and the mercury evaporates back.
With daily operation the mercury get "stirred up" enough so there is enough mercury even for the next start.

This is also pretty common with old neon signs, if parts of the tubes are dim just give then a good spin and shake to distribute the mercury they will normally come back to life, but don't do it before you buy it or the price will go up as the brightness increases back to there former glory..