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Author Topic: Big gray spot in fluorescent bulb  (Read 4448 times)

Offline mr_big

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Big gray spot in fluorescent bulb
« on: October 05, 2005, 02:19:04 pm »
In a new fluorescent light there is this big gray spot that looks like it is made up of hundreds of little dark spots anybody know what this is

Offline Zelandeth

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Re: Big gray spot in fluorescent bulb
« Reply #1 on: October 05, 2005, 05:21:45 pm »
Without seeing it, hard to say.  Chances are that it's condensed elemental mercury though.  You will also occasionally see this if a lamp has been chilled for an extended period then run up.  The mercury will natrually consense in the coldest location.

I've seen that phenomenon to some extent in new linear fluorescents, though not in CFL's that I can remember.  If it disappears, that's probably what it was.  If not, possibly a defect in the phosphor coating.

Think this is another point where photos can speak a thousand words though.

Offline mr_big

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Re: Big gray spot in fluorescent bulb
« Reply #2 on: October 06, 2005, 01:10:00 pm »
I turned the lamp verticle to see if it would go away and it pretty much did except for a few little spots