POLL: Would you use a cracked bulb?

[Kirks518]

I picked up a used Quantum flash unit, as I needed a bulb. At $55+, wasn't keen on buying a bulb. I picked up a working flash unit, with reflector (needed a second one as well), and bulb. Unfortunately, the outer glass casing of the bulb is cracked. Because I like to live on the edge, I put the reflector on with the diffuser, and fired it a few times from 1/64th to 1/1, and it fired fine.

Since the area that has the cracking is the outer (protective?) shell and not the part that fires, would you use it? This would not be used for people portraits, but mostly for still life and florals.

 

[AgX]

I would either tape or cement that crack.

 

[John Koehrer]

You can try a UV cure glass cement, but I don't think I'd use it with
anything alive.
Think about liability, using a known defective tool and having it shatter on a person.

 

[AgX]

That bulb is not pressure loaded during firing, other than an untight flash bulb.

In the worst case it has to keep fragments from a shattering flashtube.

 

[Kirks518]

Yeah, it has an opening at the top, so definitely no pressure load. I was worried more about the heat causing it to crack more, but I think the biggest concern would be if the actual strobe popped, the glass shell (?) wouldn't keep it contained. What about when the bulb dies? Would that be a time of concern?

I'm not worried about it causing injury to anyone other than myself, as I won't be using this one for portraits or anything with people in it. I would be the only one around.

 

[AgX]

That bulb is not pressure loaded during firing, other than an untight flash bulb.

In the worst case it has to keep fragments from a shattering flashtube.

Or in case of heat induced stress that crack will expand and one might end with the bulb falling off in two parts.
That is the worst scenario I can imagine.


But my imagination might be limited...

 

[MartinCrabtree]

How much is the camera you plan to use it on worth? I have customers that spend $40K USD on a motorcycle and complain about an $11 oil filter. What??

 

[Kirks518]

It's off camera. But it'll be used with Mamiyas (M645 1000s, RB67, C330) mostly.

 

[Mr Bill]

The only thing I'd be worried about is what caused the crack and how likely it is to continue. My guess is that the tube was somehow dropped or knocked against something, and that it's mechanical damage. It's easy enough to mark (or measure) the end of the crack so you'll know if it's progressing.

I'd say it's most likely that the glass cover is there to block UV; perhaps the flashtubes are quartz glass. A secondary purpose is to keep one's fingers off the trigger coil as well as make flashtube replacement simple.

Although flashtube exploding might be a possibility, my experience doesn't bear this up. I don't recall hearing about any, and I spent years as the Quality Control manager in the main processing lab of a large chain studio outfit. We had thousands of studios, each one shooting in the general range of 100 thousand shots per year. We serviced all of our own equipment, and had a full time QC inspector screening all the repaired gear, so I was sort of keyed in to problems. Again, I don't recall any issues with exploding flashtubes, nor cracked glass shields for the matter. This doesn't really prove anything, but I would just be skeptical that such a thing really happens; does anyone here have any first-hand knowledge of such?

 

[AgX]

Although flashtube exploding might be a possibility, my experience doesn't bear this up.

Actually it is hard to imagine for me too. Unlike a flash bulb a electronic flash if untight should not even ingnite.
Maybe there is a state of too few air inside to hamper ignition and enough to raise pressure at ignition to make the tube brake.



But too high capacitator charge and its thus too high arc current should be detrimental for the flash tube.
A situation that could not come up with integral electronic flashes.
But with loose flash heads and generator banks...

 

[Mr Bill]

But too high capacitator charge and its thus too high arc current should be detrimental for the flash tube.

Yes, I think so too, but I think a different failure mode. At one time we had a piece of equipment running at a certain power setting; at the same time we had some residual equipment with a plug-compatible flash tube with less than half the power rating. Anyone who's ever been in a large organization with relatively unqualified people knows that it's just a matter of time until someone manages to get the low-rated flashtube into the higher-powered equipment.

I put the question to the manufacturer, what would happen? They said that the lower-rated tube would be made of glass, and initially it should work fine. But before too long the glass would begin developing microcracks, the gas would begin leaking out, and the tube would cease firing. Normally we would verify such a thing ourselves, but not in this case because we decided to pull all the low-rated tubes out of service. So I never saw for myself, but neither did I hear of any catastrophic failures so I tend to believe the flash engineers.

 

[Sirius Glass]

If that was the only flashbulb that I had, I would use it.