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What is the blue dot in a flashbulb, anyway?

 
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Baker



Joined: 08 Apr 2002
Posts: 85
Location: Texas

PostPosted: Wed Jul 09, 2003 4:44 am    Post subject: Reply with quote

I have several boxes of old Sylvania flashbulbs that I use with my Speed Graphic. The flashbulbs, of course, have our friend the Little Blue Dot that turns pink when regular air hits it, alerting us to a breach in the bulb, which would lead to not-as-bright-as-it-should-be flashyness and possibly subject's-face-slicing-to-ribbons-shower-of-hot-glass shatteryness. (and yes, I'm concerned about them in that order: A defective flash is my problem; it prevents me from getting the picture. The red-hot bits of glass and burning tungsten are going away from me; ergo, Somebody Else's Problem )

But what is the blue dot? What mysterious chemical is it made of that magically senses when the bulb is cracked?




Disclaimer: the parenthetical statement is for amusement purposes only; my 5" reflector has the optional clear plastic cover that prevents that sort of thing from happening.
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Stephen Furley



Joined: 11 May 2001
Posts: 79
Location: London, England

PostPosted: Sun Aug 17, 2003 1:12 pm    Post subject: Reply with quote

I believe it's cobalt chloride, which is turned pink by the moisture in the air, if it (the air) leaks into the bulb.
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RichS



Joined: 18 Oct 2001
Posts: 1467
Location: South of Rochester, NY

PostPosted: Mon Aug 18, 2003 3:17 pm    Post subject: Reply with quote

I always thought the ones with pink dots were the girl bulbs?


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Graflite



Joined: 08 Nov 2001
Posts: 103
Location: Southeast US

PostPosted: Mon Aug 18, 2003 5:17 pm    Post subject: Reply with quote

This may be the reason why the flash bulbs had to be kept separated from each other inside the box, to keep the "boy bulbs" from getting to the "girl bulbs".

However I had hoped that they would mix and produce more flash bulbs, (rather like rabbits) to replace my dwindling supply of bulbs .

But then I wondered if a Press 50 Blue from a respected family could really find a lasting love with a lowly M3B from the other side of the tracks?

However I think in one hot moment of contact as the electricity flowed between them that they would both go up in smoke and it would be forever over with them.

graflite
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RichS



Joined: 18 Oct 2001
Posts: 1467
Location: South of Rochester, NY

PostPosted: Mon Aug 18, 2003 6:08 pm    Post subject: Reply with quote





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Les



Joined: 09 May 2001
Posts: 2682
Location: Detroit, MI

PostPosted: Mon Aug 18, 2003 7:31 pm    Post subject: Reply with quote

I had two number 5s mate in the pocket of my polyester double knit leisure suit when I was shooting a wedding. Rather than ending up with more bulbs, I got a pair of brown plastic trousers fused to my thigh.
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Graflite



Joined: 08 Nov 2001
Posts: 103
Location: Southeast US

PostPosted: Mon Aug 18, 2003 10:03 pm    Post subject: Reply with quote

Les:

OUCH!!! I've heard of that happening, but was lucky it never happened to me, I've heard it happens with certain kinds of clothing (i.e.: polyester) and static electricity, but it's so damm humid here in Florida (even indoors) that even so, it might still happen to me if I'm not careful).

More reason for me to get off my lazy rear and build that "retro" flash using a flash strob tube and circuit from a Globe Strob 500 and mate it with a 3 cell battery tube and a 7 inch reflector.

Rather than trash a good Globe Strob 500 to build this, I have acquired the parts list for the Globe Strob 500 and will order the same parts from an electronics supplier.

With these new parts and the parts from a non-working #2773 handle and a damaged Globe Strob 250, I can then build the "retro" flash without sacrificing a working unit.

The best of two worlds with a flashgun that doesn't look out of place on my '59 Crown and the convenience of not having to carry and dispose of flash bulbs.

The only downside would be having to carry a battery pack on the shoulder, but I already do that anyway with the Strob 500.

graflite

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