580EX with gel made funny noise and smell

[gooble]

I was shooting through some gels on my 580EX flash. I put up a dark mustard yellow gel on the flash which was on camera at 1/4 power. I took a picture and there seemed to be a noticeable pop and a smell. At first I thought I'd blown a cap. I fired the flash again at lower power and it still flashed. I pulled it off the camera and sniffed it. It was something like a burnt plasticky electrical smell that reminded me a little of those growing snake fireworks things.

I pushed the test flash button and it still fired. I inspected the gel and noticed that it smelled the same and has a discolored spot on it. Apparently the flash was hot enough to melt the gel a little bit.

Is this normal at 1/4 power? Was it because the gel was so dark, maybe .6-.9ND worth, absorbing the heat of the flash. What was the noticebable pop noise?Anyone ever had this happen?

Edit: thought I'd add that there was no visible melting or discoloration to the diffuser on the flash, it just smells like the burnt gel.

[Curtis N]

Gels get hot, fast. Any light that doesn't pass through it is instantly converted to heat.

Make sure you mount the gel in a way that leaves an air gap between the gel and the flash lens.

[SYS]

Depending on how you mounted the gel, the pop sound is most likely from the gel vibration upon a load of light hitting its surface...

[lazer-jock]

Interesting... Light does have mass (that whole Relativity Theory going on here), but I have never heard of a flash putting out enough light to move something. I'd have to sit down and do the calculations, but I am guessing that the movement is a nearly explosive expansion of the rapidly heated air that is slightly confined by the gel. Just my initial thoughts...

That being said, I have seen people drop gels between the lens of their flash and the wide angle diffuser. It always makes me nervous (even if it isn't my equipment) because I know these gels can melt pretty easily (good thing swatchbooks are cheap).

[SYS]

Interesting... Light does have mass (that whole Relativity Theory going on here), but I have never heard of a flash putting out enough light to move something. I'd have to sit down and do the calculations, but I am guessing that the movement is a nearly explosive expansion of the rapidly heated air that is slightly confined by the gel. Just my initial thoughts...

You got me curious, so I just ran a little test where I simply held one of the Roscolux sample gel directly in front of the flash at 1/4th of power and popped some flashes. No detectable movement or sound. If the gel was confined in an air tight gadget of some kind, would that have made a difference... ? I don't know. But at this point my above guess is most likely wrong.

That being said, I have seen people drop gels between the lens of their flash and the wide angle diffuser. It always makes me nervous (even if it isn't my equipment) because I know these gels can melt pretty easily (good thing swatchbooks are cheap).

Yea, those are cheap, but scraping the melted cheese off the flash head can be a long labor... ;)

[lazer-jock]

Well, a quick google search says that Rosco gels start to melt at 300 °C. Assuming that you're in a temperate part of the world, your air temp will be around 25 °C. Throwing that into the Ideal Gas Law, you would have nearly instantaneous (sub-millisecond) doubling of the pressure of the air from that temperature change which would then dissipate quickly past the sides of the gel. I could see that giving a little pop or rattle to the relatively flimsy gel. I would have to rig up an experiment to see how much of an effect there really is.

[gooble]

Gels get hot, fast. Any light that doesn't pass through it is instantly converted to heat.

Make sure you mount the gel in a way that leaves an air gap between the gel and the flash lens.

I will be more careful in the future.

Depending on how you mounted the gel, the pop sound is most likely from the gel vibration upon a load of light hitting its surface...

After looking at the gel I used, a Lee 741 Mustard Yellow on page 153 of the sample book (anyone want to replicate my experiment?), I could see that it was warped. My guess is that the rapid heating and subsequent melting movement of the gel made the pop sound.

You got me curious, so I just ran a little test where I simply held one of the Roscolux sample gel directly in front of the flash at 1/4th of power and popped some flashes. No detectable movement or sound. If the gel was confined in an air tight gadget of some kind, would that have made a difference... ? I don't know. But at this point my above guess is most likely wrong.

Yea, those are cheap, but scraping the melted cheese off the flash head can be a long labor... ;)

Were any of the ones you tested very dark? The Lee mustard yellow I used was quite dark absorbing more heat that most gels would I assume.

[SYS]

Were any of the ones you tested very dark? The Lee mustard yellow I used was quite dark absorbing more heat that most gels would I assume.

No, not for the test, but in the other post regarding my DIY gel holder, I can tell you that after many pops, the laminated gel holds up really well.

[mattograph]

Were you holding the gel in place with the wide angle diffusion panel?

[gooble]

Were you holding the gel in place with the wide angle diffusion panel?

No. The WA diffuser was not pulled out. The gel was still attached to the Lee swatch pack and I just held it up by hand.

[Hermes]

All gels in sample books should have their transmission stats listed next to them (usually as a percentage). You'll find that many of the deep colour-effect gels absorb a huge percentage of light compared to standard colour correction gels which means it takes a lot less flash power to overheat them. Also worth noting that both Lee and Rosco have different ranges of gels designed for different applications and light sources - what type of gel swatchbook is it that you have?

[dpds68]

Will I be ok if I stuck the Gel where the wide angle diffuser goes on the Vivitar 285Hv ?